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1.
Tongfa Liu Yuli Xiong Anyi Mei Yue Hu Yaoguang Rong Mi Xu Zheng Wang Lingyun Lou Dongjie Du Shizhao Zheng Xia Long Shuang Xiao Shihe Yang Hongwei Han 《RSC advances》2019,9(51):29840
The spacer layer is a key component of fully printable mesoscopic perovskite solar cells, but its precise characteristics are far from being understood in relation to the device design. In the present work, we perform a detailed systematic study on the effects of spacer parameters, such as size of building blocks, layer thickness, etc., on properties of the perovskite filler, insulating ability and performance of fully printable mesoscopic perovskite solar cells by combining the techniques of time-resolved photoluminescence, high-resolution TEM, insulating resistance measurements, impedance spectroscopy and J–V characteristics. Drawing on the deep understanding from these studies, we formulate key principles, which are anticipated to guide the design of the advanced spacer layer for fully printable mesoscopic perovskite solar cells.Key principles and reasonable routes are proposed to advance the spacer layer design for fully printable mesoscopic perovskite solar cells.Lead halide perovskite (PVSK) as a promising semiconducting material has been introduced as a light harvesting semiconductor because of its ease of fabrication and excellent physical properties, such as tunable bandgap, strong absorbance, long carrier diffusion length and shallow intrinsic trap state level.1–9 Extremely flat and compact perovskite thin film with large crystal size has gained particular attention to boost power conversion efficiency (PCE) by sequential deposition method, vapor deposition, solvent-annealing, solvent engineering, hot-casting method, intramolecular exchange methods, and additive, etc.10–16 Benefiting from rapid improvements in formation of high quality perovskite thin film, a certified PCE of 25.2% has been achieved.17 However, illumination stability in real environment still remains a serious challenge due to the inherent moisture and UV sensitivity of perovskite. Moreover, using expensive and rare metals as back contact, such as gold and silver, may limit large-scale production in the future. As the competing architecture of perovskite solar cells, TiO2/spacer/carbon (abbreviated as TSC) films based fully printable mesoscopic perovskite solar cells (FP-MPSC) have attracted a lot of researchers due to their low cost and printable large-scale production process.18–21 In this type of solar cell, carbon can efficiently collect hole from perovskite layer even without any other hole transporting materials.22,23 Most importantly, FP-MPSC could work with excellent illumination stability and heat-stress stability by filling TSC films with (5-AVA)xMA1−xPbI3 (5-AVA = 5-aminovaleric acid, MA = methylammonium), although the efficiency of 12.8% is still far behind from the most efficient solar cell.16,21,24Spacer, as an important part of FP-MPSC, plays a crucial role in obtaining high performance device. Basically, the spacer layer mainly burdens triple important tasks in the efficient mesoscopic perovskite solar cells. Firstly, the core function of spacer is to separate anode and cathode and to prevent electrons in TiO2 from transporting directly to carbon electrode. The separating property of spacer depends on spacer particle sizes, morphology, materials, etc. This requires that spacer layer has no cracking and has wide bandgap. Secondly, the perovskite confined in the mesopores of spacer layer can absorb photons transmitted through perovskite/TiO2 composite layer and have contribution to photocurrents. Thirdly, the holes produced in the perovskite/TiO2 composite layer have to go through perovskite/spacer composite layer to reach carbon electrode. And the electrons produced in the perovskite/spacer composite layer have to go through perovskite/spacer composite layer to reach TiO2 electrode. Because spacer layer has these important functions, some research on spacer layer have been carried out. Recently, Al2O3 or ZrO2 spacer layer was compared with respect to their pore size.25 However, conclusion of the effect of pore size in two different materials was incomplete. The effect of spacer layer thickness was simply discussed both in monolithic dye-sensitized solar cells and FP-MPSC.20,26 The morphology of spacer layer was also improved to increase PCE of FP-MPSC.27 Although these researches made some progress, there are no clear standards that what should an ideal spacer layer satisfy. Therefore, it is urgent to carry out detailed study on how the parameters of spacer affect the above functions and performance of mesoscopic printable perovskite solar cells.In the present study, the effects of size of building blocks of spacer layer, thickness of spacer layer on property of perovskite crystals, insulating property, and performance of mesoscopic perovskite solar cells were investigated in details. Based on these deep understandings, critical principles to design advanced spacer layer are proposed.ZrO2 is used as spacer material due to its large band gap and high conduction band energy level. There are five different sizes of spacer building blocks in this study. The average particle sizes of spacer are measured to be about 5 nm, 10 nm, 20 nm, 60 nm and 100 nm, respectively, and hereafter referred to as S5, S10, S20, S60, S100 spacer, respectively. SEM images of as-prepared spacer films using these building blocks are shown in Fig. 1. X-ray diffraction patterns of spacer film with different particle sizes are presented in Fig. 1f, indicating that the five spacer films were all tetragonal crystal phase as majority phase. From Scherrer equation, the crystal sizes of spacer building blocks were calculated to be about 5 nm, 10 nm, 20 nm, 30 nm, 30 nm, respectively. These results indicated that the S60 and S100 particles are consisted of 30 nm sized crystal ZrO2. Fig. 1 presents that there is a large difference in surface morphology with particle size increasing. There are cracks in S5 and S10 spacer films and micrometer scale pores exist in the S100 spacer, while the surface of S20 and S60 are very uniform without defects.Open in a separate windowFig. 1SEM images of spacer films with particle size of 5 nm (a), 10 nm (b), 20 nm (c), 60 nm (d) and 100 nm (e), respectively. (f) XRD patterns of spacer film with different building block sizes.During solvent evaporation of perovskite precursor, perovskite crystal growth is restricted by randomly interconnected mesopores of spacer film, leading to nanoscale crystal size and random crystal orientation, as observed by high resolution transmission electron microscope (Fig. 2a), in which clear crystal lattices of perovskite crystals can be distinguished from spacer particles. Meanwhile, the mesopores of spacer film is fulfilled with perovskite materials, providing continuous channels for charge carriers. The crystal size of perovskite material in spacer film is strongly influenced by mesopore size of spacer layer, as seen in XRD intensity of perovskite at 2θ of about 14.2° (Fig. 2b). There is an apparent trend that the intensity increased with increasing the particle size of spacer film. As a reference, perovskite was also deposited on bare glass, which exhibited the best crystallinity. The calculated sizes of perovskite from XRD spectra are 4.3 nm, 3.9 nm, 6.2 nm, 11.5 nm, and 12.6 nm, respectively, for the S5, S10, S20, S60, and S100 spacer layer. Apparently, the sizes of perovskite crystals confined in the spacer layer are smaller than the average pore sizes of spacer layer measured by N2 absorption/desorption isotherms (Table S1†). The high-resolution TEM image also gives consistent results. For example, the sizes of perovskite crystals confined in the S20 spacer layer are between 8.4 nm to 12.7 nm measured in the TEM image (Fig. 2a). The infiltrated perovskite started to nucleate onto the heterogeneous surface of spacer building blocks with high surface area, resulting to multiple nucleation centers and small crystal size. In order to evaluate the effect of spacer particle size on physiochemical properties of perovskite, the band-edge emission spectra of perovskite/spacer composite film were measured in Fig. 2c. The band-edge emission spectrum of perovskite deposited on bare glass peaked at 762 nm (with photon energy of 1.627 eV). As the particle size of spacer film decreased, a blue shift of the band-edge photoluminescence occurred, and linewidth broadened. The peak position of perovskite emission spectra can be tuned in the range of 33 nm through varying the pore size of spacer film. The increase of emission line width at grain boundaries can be attributed to disorder and defects of perovskite,14,15 which also led to the decrease of lifetime in time-resolved PL (Fig. 2d). Perovskite film grown on glass has the lifetime of 141.9 ns. However, perovskite grown in spacer film decreased to 0.5 ns, 8.4 ns, 24.1 ns, 37.2 ns, 53.7 ns, for S5, S10, S20, S60, S100, respectively.Open in a separate windowFig. 2(a) High resolution transmission electron microscope image of perovskite/S20 spacer film composite. (b) XRD of perovskite/spacer film composite. (c) Steady PL emission spectra and (d) time-resolved PL of perovskite/spacer film composite.The particle size of spacer also has large effect on insulating ability of spacer films with the same thickness. FTO/spacer/carbon configuration was designed to measure the insulating ability of spacer layers. In ideal conditions, the resistance between carbon and FTO, defined as insulating resistance (RI), should be infinite, indicating that there is not any leakage current from ideal insulating spacer. However, all of the measured resistance has finite values, summarized in 28–31Photovoltaic parameters of mesoscopic perovskite solar cells based on spacer with different building block sizes
Open in a separate window Fig. 3a is the scheme showing the layout of FP-MPSC. The influence of the size of spacer layer building block on the photocurrent density–voltage (J–V) curves of the (5-AVA)xMA1−xPbI3 perovskite devices without and with spacer layer was evaluated in Fig. 3b and photovoltaic parameters are summarized in 20 The VOC increased significantly from 605 mV to above 808 mV, when the device added spacer layers. The device with S100 spacer, which had best crystallinity and longest photoluminescence lifetime, is expected to have excellent performance. But S100 spacer has relatively low VOC of 808 mV and low PCE of 10.10%. This is resulted from poorest insulating ability of S100 spacer among these spacer films. Balancing from photoluminescence property of perovskite confined in spacer layer and insulating property of spacer layer, 20 nm-sized S20 spacer film had the best performance with efficiency of 11.86%. It is common sense that devices with large perovskite crystal size with low trap density can approach VOC to the limit of theoretical value.1,32,33 The blue shift of the band-edge photoluminescence and decreased lifetime of perovskite in spacer film may explain the relatively low VOC (less than 1.0 V) relative to conventional planar perovskite solar cells (VOC was more than 1.1 V) in which the size of perovskite crystal was larger than 500 nm. Spacer film with large pore size and excellent insulating property are expected to further improve VOC of FP-MPSC. The observed quantum size effect of perovskite nanocrystals confined in spacer mesopores in some extents results from templating effect of spacer nanoparticles and unmatched crystal lattices. Matched crystal lattices may mitigate the quantum size effect by heteroepitaxy via reduced nucleation density.34Open in a separate windowFig. 3(a) Scheme showing the layout of FP-MPSC. (b) J–V curves of devices based on spacer film with different building block sizes.The effect of thickness of spacer film on mesoscopic perovskite solar cells was briefly discussed in our previous study.20,35 Here, detailed study from the points of insulating ability and impedance was carried out to clarify the mechanism on how spacer film affects the performance of FP-MPSC.All photovoltaic parameters depended on the thickness of spacer film (Fig. 4a). Dark current (Fig. 4b) is suppressed by increasing thickness of spacer film, which is in good agreement with that VOC reached maximum value and remained stable when thickness is above 2.64 μm. The VOC has coincident trends with insulating resistance in Fig. 4c. Therefore, VOC has strong relationship with insulating ability of spacer film when other conditions are the same. JSC reached maximum value and remained stable when thickness is above 3.31 μm by harvesting more photons. JSC decreased with over 5 μm-thick spacer layer resulted from recombination. PCE reached maximum value when thickness is about 4.84 μm. The device without spacer film has poorest VOC, so there is a need to avoid the damage of spacer film when screen printing of carbon film onto spacer film. The dependence of JSC on thickness of spacer film and different trends between JSC and VOC indicate that perovskite confined in spacer film can generate charge carriers, playing similar role of perovskite capping layer in conventional mesoporous/planar bilayer perovskite solar cells. The fill factor (FF) was not linearly decreased when thickness of spacer film was increased, although the transporting distance of charge carriers was increased. This result was different from dye-sensitized solar cells, where FF was linearly decreased when thickness of spacer film was increased.26Open in a separate windowFig. 4(a) Photovoltaic parameters dependence on thickness of S20 spacer film. (b) Dark current of FP-MPSC based on different thickness of spacer film. (c) Insulating resistance (RI) of spacer film with different thickness.To further elucidate the relation between thickness of the spacer film and the photovoltaic performance, impedance spectra (IS) were measured. Before analyzing the spectra, physical process correlated to each semicircle should be identified qualitatively. Up to now, IS analysis on fully printable mesoscopic perovskite solar cells simply applied existing models of dye-sensitized solar cells or planar perovskite solar cells. To assure reliability, IS are analyzed by varying thickness of spacer film, with or without meso-TiO2 to assign high frequency and low frequency semicircles. The photographs of devices used to measure the IS are shown in Fig. S1 and S2.† The typical Nyquist plot and Bode plot of the FP-MPSC device with different spacer film thickness measured at 0.3 V, under weak illumination was plotted in Fig. 5. The full IS can be found in Fig. S3 and S4, in the ESI.† The IS in high frequency part was modelled with one resistance paralleling with one constant phase element and adding another series resistance, as depicted in Fig. S5.† The fitting resistance and capacitance was normalized with active area, as presented in Fig. 6. Under weak light (0.1 sun), series resistances (Rs) are almost between 10–15 Ω cm2, remaining constant in the whole bias voltage range while high frequency resistances (RPerovskite) increased clearly with increasing thickness of spacer film and associating capacitance decreased with increasing thickness of spacer film. The change in high frequency semicircle is not related to carbon/perovskite interface because the contact of carbon/perovskite interface was unchanged. Therefore, the change in high frequency semicircle is originated from thickness varying of spacer film. Integrating the above features, it is concluded that low frequency semicircle is related to TiO2/perovskite interface, which is in good agreement with the usual understanding that charge carrier recombination in TiO2/perovskite interface is slow process, and high frequency semicircle is related to both perovskite confined in spacer film and carbon/perovskite interface. This was consistent with other researcher''s results in which one extra feature related to perovskite was observed from high to intermediate frequency.36 The new feature leads to abrupt decrease of phase value of constant phase element below 0.4 V, as can be clearly seen in Fig. 6d. The new feature is also clear in the Nyquist plot and Bode plot in Fig. 5b and c, where two RC circuit components merge at high frequency (104–105 Hz). One simple model to interpreting this new feature is to consider the perovskite/spacer composite layer as a standard parallel plate capacitor, and the capacitance can be written as eqn (1).C = ε0εS/d1where ε0 is vacuum dielectric constant, ε is relative dielectric constant of perovskite, S is the active area of device, and d is the thickness of spacer layer. Because the spacer layer is wide bandgap materials, there is little charge in the spacer itself. The charge transport is mainly from perovskite confined in the spacer layer. The normalized capacitance with active area will be reciprocal of d, which is in good consistent with the trend of fitting capacitance (RPerovskite, in Fig. 6c). Based on the above results, it can be concluded that the extra feature in high to intermediate frequency is resulting from charge transport of perovskite confined in the spacer layer. This conclusion is very consistent with the analysis of the geometrical capacitance of the perovskite layer in the planar perovskite solar cells.37 The thick spacer layer of over 2.5 μm with enough insulating ability would definitely increase the charge carrier transport length through the spacer layer and cause severe recombination considering the relatively smaller perovskite nanocrystals.Open in a separate windowFig. 5Nyquist plot (a and b) and Bode plot (c) of the FP-MPSC device with different spacer film thickness measured at 0.3 V, under weak illumination (0.1 sun).Open in a separate windowFig. 6Parameters obtained from high frequency (∼102–106 Hz) semicircle IS analysis of the FP-MPSC device with different spacer film thickness measured at between 1.1 V and 0 V, under weak illumination (0.1 sun). (a) Series resistance. (b) Resistance related to perovskite. (c) Capacitance related to perovskite and (d) associated constant phase value.Combining the analysis about the effect of building block size and thickness of spacer layer, the bottlenecks of current spacer layer and infiltrated perovskite are summarized in left picture of Fig. 7. Perovskite layer embedded in mesoporous matrix of spacer layer are usually composed of crystals with size of tens of nanometers. Although observed quantum size effect may have useful application in LED or other optoelectronic fields, the limited charge transport ability in quantum dots is detrimental for achieving high PCE in photovoltaic device due to serious charge carrier recombination. Moreover, the thickness of spacer layer has to be several micrometers to insure enough insulating ability, which further hinders the charge transport to charge carrier selective layer. These two unfavorable factors decrease the potentially achievable PCE. It has been proved that grain boundaries are not beneficial for attaining high performance perovskite solar cells.1 Monolayer perovskite crystals in vertical direction are usually deposited on charge-selective layer in order to reduce recombination near grain boundary. According to the absorption coefficient of MAPbI3 perovskite, 1 μm thick MAPbI3 perovskite layer can absorb over 95% incident light at wavelength of 750 nm.15,33 Fixing the porosity of spacer layer to be 40%, 2.5 μm thick spacer layer has equivalent 1 μm thickness of perovskite layer. Considering that the size of perovskite crystals is less than 100 nm, the ratio of length of spacer thickness to size of perovskite crystals is over 25, which means that charge generated in spacer/perovskite layer has encountered at least 25 grain boundaries before reaching charge selective layer. To overcome these issues, the ideal features of spacer layer and infiltrated perovskite are illustrated in right picture of Fig. 7. Porous single-crystal perovskite models grown in matrix of porous spacer template with 2D arrays or 3D of structured films are more favorable for achieving high PCE.38 Perovskite nanorod has high mobility due to confined charge transport. It is known in the zeolite field that meso-crystal materials can grow from one ordered template, which needs controlled template–precursor interaction.39–41 In fact, porous single crystal MAPbI3 has been realized via additive in perovskite precursor solution.42 Some favorable phenomena has been also observed in investigating the crystallization of perovskite in mesopores of TSC films. For example, the crystal growth with preferential orientation was realized via moisture-induced crystallization process in the NH4Cl–PVSK complex.43 Even the perovskite crystal growth was significantly templated by scaffold, pronounced positive effect was occurred in photovoltaic performance. Therefore, exploring methods to grow mesoporous single-crystal perovskite with less grain boundaries and higher mobility in ordered spacer layer would further promote PCE of FP-MPSC device.Open in a separate windowFig. 7Illustration to show problems of current spacer layer and infiltrated perovskite, and proposed features of ideal spacer layer and infiltrated perovskite.Another issue to overcome is the unideal insulating ability of spacer film. The melting point of ZrO2 is about 2700 degrees. Sub-micrometer to nanometer ZrO2 is usually used to decrease the sintering temperature below 1000 degrees in the ceramic field.31 The particle size of ZrO2 has to be small enough to be sintered at allowed temperatures (the FTO glass will soften when T > 550 degrees).44 The insulating ability is mainly associated with porosity and interparticle connection. The porosity is similar for all particle size. The different insulating ability arises mainly from interparticle connection. To improve insulating ability, low-melting point wide bandgap nanomaterials is preferred as building blocks. Aluminum oxide, silica, or ternary oxides may provide better choice as spacer building blocks.45 Recently, by depositing a thin layer of Al2O3 onto surface of mesoporous TiO2 before printing spacer layer, the ZrO2 thickness was reduced from 3 μm to 1.2 μm while retaining comparable device performance.35 相似文献
| Spacer | Lifetime (ns) | R I (Ω) | J SC (mA cm−2) | V OC (mV) | FF (%) | PCE (%) |
|---|---|---|---|---|---|---|
| No spacer | — | 30 | 16.21 | 605 | 66 | 6.52 |
| S5 | 0.5 | 1500 | 16.06 | 871 | 67 | 9.42 |
| S10 | 8.4 | 970 | 18.26 | 908 | 71 | 11.77 |
| S20 | 24.1 | 960 | 19.10 | 871 | 71 | 11.86 |
| S60 | 37.2 | 800 | 18.19 | 865 | 70 | 11.08 |
| S100 | 53.7 | 300 | 18.62 | 808 | 67 | 10.10 |
2.
Suyuan Zhou Tao Zhu Luyao Zheng Dong Zhang Wenzhan Xu Lei Liu Gang Cheng Jie Zheng Xiong Gong 《RSC advances》2019,9(52):30317
Perovskite solar cells have been rapidly developed in the past ten years. It was demonstrated that the interfacial layer plays an important role in device performance of perovskite solar cells. In this study, we report utilization of a photoinitiation-crosslinked zwitterionic polymer, namely dextran with carboxybetaine modified by methacrylate (Dex-CB-MA), as an interfacial layer to improve the film morphology of the CH3NH3PbI3 photoactive layer and the interfacial contact between the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hole extraction layer and CH3NH3PbI3 photoactive layer. It is found that the Dex-CB-MA thin layer forms a better band alignment between the PEDOT:PSS hole extraction layer and CH3NH3PbI3 photoactive layer, and improves the crystallization of the CH3NH3PbI3 photoactive layer, resulting in efficient charge carrier transport. As a result, perovskite solar cells with the PEDOT:PSS/Dex-CB-MA hole extraction layer exhibit more than 30% enhancement in efficiency and dramatically boosted stability as compared with that with the PEDOT:PSS hole extraction layer. Our studies provide an effective and facile way to fabricate stable perovskite solar cells with high power conversion efficiency.The zwitterionic polymer, Dex-CB-MA thin layer forms a better band alignment between the PEDOT:PSS hole extraction layer and CH3NH3PbI3 photoactive layer, and improve the crystallization of CH3NH3PbI3 photoactive layer, resulting in efficient charge carrier transport. 相似文献
3.
Mukerem Helil Abib Junchun Li Heming Yang Man Wang Taotao Chen EnzeXu Yang Jiang 《RSC advances》2021,11(6):3380
All inorganic carbon-based planar perovskites, particularly CsPbBr3, have attracted considerable attention due to their excellent stability against oxygen, moisture, and heat for photovoltaic utilization. However, the power conversion efficiency of carbon-based planar CsPbBr3 perovskite solar cells is mostly low, primarily because of the inferior film quality with undesirable crystallization and narrow light absorbance ranges. Herein, we develop a novel direct deposition approach combined with Sn doping to achieve highly efficient and stable carbon-based Sn-doped CsPbBr3 perovskite solar cells. Mass-scale Sn ion-doped CsPbBr3 perovskite powder was effectively synthesized and characterized via a facile strategy by adding hydrohalic acid in the CsBr, PbBr2 and SnBr2 precursor in a dimethyl sulfoxide solution. Moreover, using the as-synthesized CsPbBr3 and Sn-doped CsPbBr3 perovskite powder, PSCs were obtained via effective direct thermal evaporation. A smooth, constant and pinhole-free perovskite film was achieved with a configuration of FTO/TiO2/Sn:CsPbBr3/carbon. PSCs based on Sn:CsPbBr3 as an absorber and carbon as the HTM achieved an impressive power conversion efficiency of 8.95% compared to 6.87% for undoped CsPbBr3; moreover, it displayed admirable stability in an open-air atmosphere for an operational period of about 720 h without a noticeable negative result. The introduction of the Sn ion may advance the interface extraction of charge between the electric transport layer to the absorber layer and absorber to the carbon electrode. Accordingly, the Sn ion doping on CsPbBr3 during the synthesis phase and the direct evaporation paves a novel approach for intended photovoltaic applications.All inorganic carbon-based planar perovskites, particularly CsPbBr3, have attracted considerable attention due to their excellent stability against oxygen, moisture, and heat for photovoltaic utilization. 相似文献
4.
In recent times, perovskite solar cells (PSCs) have been of wide interest in solar energy research, which has ushered in a new era for photovoltaic power sources through the incredible enhancement in their power conversion efficiency (PCE). However, several serious challenges still face their high efficiency: upscaling and commercialization of the fabricated devices, including long-term stability as well as the humid environment conditions of the functional cells. To overcome these obstacles, stable graphene (G) materials with tunable electronic features have been used to assist the crystallization as well as the charge extraction inside the device configuration. Nonetheless, the hole transport layer (HTL)-free PSCs based on graphene materials exhibit unpredictable results, including a high efficiency and long-term stability even in the conditions of an ambient air atmosphere. Herein, we combine graphene materials into a mesoporous TiO2 electron transfer layer (ETL) to improve the coverage and crystallinity of the perovskite material and minimize charge recombination to augment both the stability and efficiency of the fabricated mixed cation PSCs in ambient air, even in the absence of a HTL. Our results demonstrate that an optimized PSC in the presence of different percentages of graphene materials displays a PCE of up to 17% in the case of a G:TiO2 ETL doped with 1.5% graphene. With this coverage and crystallinity amendment approach, we show hysteresis-free and stable PSCs, with less decomposition after ∼3000 h of storage under a moist ambient atmosphere. This work focuses on the originalities of the materials, expenses, and the assembling of stable and effective perovskite solar cells.In recent times, perovskite solar cells (PSCs) have been of wide interest in solar energy research, which has ushered in a new era for photovoltaic power sources through the incredible enhancement in their power conversion efficiency (PCE). 相似文献
5.
Organometal halide perovskite solar cells are becoming one of the most competitive emerging technologies. They have reached a power conversion efficiency (PCE) of 22.7% in 10 years. Their high efficiency and simple fabrication process render perovskite solar cells a promising player in the field of third-generation photovoltaics. The deposition methods play an important role in the fabrication of a high quality films. In this paper, we report the preparation of methylammonium lead bromide (MAPbBr3) thin film using a two-step method based on the transformation of PbBr2 into MAPbBr3 perovskite after dipping in a MABr solution. The effects of the dipping time and the annealing time on the photovoltaic, optical and structural properties of the devices were studied. The dipping time treatments of the inorganic film in organic solution were conducted from 30 s to 15 min. The obtained result showed that the PCE of the devices was improved with the increase of dipping time. In addition, an increase of annealing time induces an enhancement of the perovskite properties. Furthermore, the as-fabricated perovskite solar cell dipped and annealed for 10 min exhibited the highest power conversion efficiency of 4.8% with a short circuit current density of 16.16 mA cm−2, an open circuit voltage of 0.84 V, and a fill factor of 35.50.Organometal halide perovskite solar cells are becoming one of the most competitive emerging technologies. 相似文献
6.
Shengwei Shi Jing Li Tongle Bu Shili Yang Junyan Xiao Yong Peng Wei Li Jie Zhong Zhiliang Ku Yi-Bing Cheng Fuzhi Huang 《RSC advances》2019,9(18):9946
Tin oxide (SnO2) is widely used as electron transport layer (ETL) material in perovskite solar cells (PSCs). Numerous synthesis methods for SnO2 have been reported, but they all require a proper thermal treatment for the SnO2 ETLs. Herein we present a simple method to synthesize SnO2 nanoparticles (NPs) at room temperature. By using butyl acetate as a precipitator and a proper UV–Ozone treatment to remove Cl residuals, excellent SnO2 ETLs were obtained without any thermal annealing. The highest power conversion efficiency (PCE) of the prepared PSCs was 19.22% for reverse scan (RS) and 18.79% for forward scan (FS). Furthermore, flexible PSCs were fabricated with high PCEs of 15.27%/14.74% (RS/FS). The low energy consuming SnO2 ETLs therefore show great promise for the flexible PSCs'' commercialization.Room-temperature processed SnO2 as electron transport layer materials for efficient flexible perovskite solar cells. 相似文献
7.
Xin Huang Qiuhong Cui Wentao Bi Ling Li Pengcheng Jia Yanbing Hou Yufeng Hu Zhidong Lou Feng Teng 《RSC advances》2019,9(14):7984
Methylammonium lead iodide perovskite photovoltaics have attracted remarkable attention due to their exceptional power conversion efficiencies (PCEs). The film morphology of organometallic halide perovskite plays a very important role in the performance of planar perovskite solar cells (PVSCs). Previous methods have been explored to control the crystal growth for getting a compact and smooth perovskite film. Here, we report an effective and reproducible approach for enhancing the stability and the efficiency of PVSCs by incorporating a small quantity of two-dimensional (2D) material diethylammonium iodide (DAI) in three-dimensional (3D) MAPbI3, which can facilitate the perovskite crystallization processes and improve the resulting film crystal quality. The fabricated (DA2PbI4)0.05MAPbI3 perovskite hybrid films exhibit good morphology with larger grains and uniform morphology. Simultaneously, reduced defects and enhanced carrier lifetime within a full device indicate enhanced crystallization effects as a result of the DAI inclusion. The photovoltaic device attains a high photocurrent of 22.95 mA cm−2 and a high fill factor of 79.04%, resulting in an overall PCE of 19.05%. Moreover, the stability of the 10% DAI doped perovskite solar cell is also improved. These results offer a promising stable and efficient light-absorbing material for solid-state photovoltaics and other applications.Two-dimensional diethylammonium iodide as an additive to promote crystal growth of perovskite film for efficient and stable perovskite solar cells. 相似文献
8.
Mixed-cation lead halide perovskites have emerged as a new class of promising photovoltaic materials for perovskite solar cells. Formamidinium (FA), methylammonium (MA), and Cs cations are widely studied in the field of mixed-cation hybrid halide perovskites. In this work, we have investigated ethylammonium (CH3CH2NH3, EA) as an alternative cation to explore the stabilities and electronic properties of mixed MA1−xEAxPbI3 perovskites. The results indicate that replacing MA with EA is a more effective way to improve the stabilities of the mixed MA1−xEAxPbI3 perovskites except for MA0.75EA0.25PbI3. The band gap of MA1-xEAxPbI3 slightly increases with x from 0.25 to 1.00, which is quite different from the MA–FA mixed-cation perovskites. The results indicate that the c axis distortion of the Pb–I–Pb bond angles can play a greater role in tuning the band gap. Moreover, the mixed MA1−xEAxPbI3 perovskites show comparable absorption abilities in the visible light region to the pure MAPbI3 structure. We hope that our study will be greatly helpful for further experiments to find more efficient perovskite materials in the future.Mixed-cation lead halide perovskites have emerged as a new class of promising photovoltaic materials for perovskite solar cells. 相似文献
9.
The conversion efficiencies for silicon-based photovoltaic devices have become stagnant, with the record conversion efficiency of 26.7% achieved in 2017. This record efficiency is also close to the theoretical Auger limit of 29.4% for single-junction silicon solar cells. Therefore, it is anticipated that further enhancement in conversion efficiency could only be achieved by adopting multijunction or tandem concepts for silicon PV devices. In this context, perovskites are widely preferred for tandem application with silicon solar cells to mitigate thermalization and non-absorbed photon losses to achieve higher conversion efficiencies. The perovskite–silicon (PVK–Si) tandem design can deliver 45.1% efficiency, and currently, this design holds a record conversion efficiency of 29.5%. Therefore, critical research and development activities are required to unlock the potential of such devices. Thus, we have designed and investigated enhanced hole extraction PVK–Si monolithic tandem solar cells with 33% power conversion efficiency (PCE) to make a humble contribution in this field. The device is facilitated with Me-4PACz and ITO-based ideal tunnel recombination junctions for current matching, with parasitic absorption losses. Detailed standalone and tandem analysis has been carried out in terms of absorber layer thickness variation, illuminated current density–voltage (J–V) curves, external quantum efficiency (EQE), energy band diagrams (EBDs), filtered spectra, filtered integrated power, current matching, and tandem PV parameters to finalize the conversion efficiency. The device constructed using a 1.68 eV perovskite top cell and 1.12 eV c-Si-based heterojunction with an intrinsic thin layer (HIT) based bottom cell showed an open-circuit voltage, VOC, of as high as 2.02 V. The comprehensive analysis of PVK–Si tandem devices reported in this work may pave the way for developing high-efficiency tandem solar cells in the future.The conversion efficiencies for silicon-based photovoltaic devices have become stagnant, with the record conversion efficiency of 26.7% achieved in 2017. 相似文献
10.
The standard dip-coating dye-loading technique for dye-sensitized solar cells (DSSCs) remains essentially unchanged since modern DSSCs were introduced in 1991. This technique constitutes up to 80% of the DSSC fabrication time. Dip-coating of DSSC dyes not only costs time, but also generates a large amount of dye waste, necessitates use of organic solvents, requires sensitization under dark conditions, and often results in inefficient sensitization. Functionalized Carboxylate Deposition (FCD) was introduced as an alternative dye deposition technique, requiring only 2% of the fabrication time, eliminating the need for solvents, and significantly reducing dye waste. In this study, FCD was used to deposit two relatively large triphenylamine-based organic dyes (L1 and L2). These dyes were sublimated and deposited in <20 minutes via a customized FCD instrument using a vacuum of ∼0.1 mTorr and temperatures ≤280 °C. FCD-based DSSCs showed better efficiency (i.e., 5.03% and 5.46% for L1 and L2 dyes, respectively) compared to dip-coating (i.e., 4.36% and 5.35% for L1 and L2, respectively) in a fraction of the deposition time. With multiple advantages over dip-coating, FCD was shown to be a viable alternative for future ultra-low cost DSSC production.Functionalized carboxylate deposition involves deposition of molecules from the gas phase and is an alternative dye loading technique to dip-coating. It was used to create a monolayer of large molecular weight dyes on TiO2, providing multiple advantages to dip-coating. 相似文献
11.
Highly crystalline CsPbI2Br films for efficient perovskite solar cells via compositional engineering
Fang He Wenzhan Xu Meng Zhang Xuan Zhang Baofu Ding Guodan Wei Feiyu Kang 《RSC advances》2019,9(52):30534
All-inorganic CsPbI2Br shows high thermal stability for promising application in perovskite solar cells (PSCs). The performance of PSCs is significantly affected by their morphology and crystallinity induced by compositional ratio, solvent/anti-solvent engineering and post thermal annealing. In this study, the compositional ratio effect of two precursors, PbI2 and CsBr, on the power conversion efficiency (PCE) of a device with ITO/SnO2/CsPbI2Br/Spiro-MeOTAD/Au structure was investigated. With the assistance of anti-solvent chlorobenzene, perovskite with a PbI2 : CsBr ratio of 1.05 : 1 showed a high quality thin film with higher crystallinity and larger grain size. In addition, the molar ratio of precursors PbI2 and CsBr improved the PCE of the PSCs, and the PSCs fabricated using the perovskite with an optimal ratio of PbI2 and CsBr exhibited a PCE of 13.34%.All-inorganic CsPbI2Br shows high thermal stability for promising application in perovskite solar cells (PSCs). 相似文献
12.
Jaeki Jeong Haeyeon Kim Yung Jin Yoon Bright Walker Seyeong Song Jungwoo Heo Song Yi Park Jae Won Kim Gi-Hwan Kim Jin Young Kim 《RSC advances》2018,8(43):24110
We herein demonstrate n-i-p-type planar heterojunction perovskite solar cells employing spin-coated ZnO nanoparticles modified with various alkali metal carbonates including Li2CO3, Na2CO3, K2CO3 and Cs2CO3, which can tune the energy band structure of ZnO ETLs. Since these metal carbonates doped on ZnO ETLs lead to deeper conduction bands in the ZnO ETLs, electrons are easily transported from the perovskite active layer to the cathode electrode. The power conversion efficiency of about 27% is improved due to the incorporation of alkali carbonates in ETLs. As alternatives to TiO2 and n-type metal oxides, electron transport materials consisting of doped ZnO nanoparticles are viable ETLs for efficient n-i-p planar heterojunction solar cells, and they can be used on flexible substrates via roll-to-roll processing.Planar formamidinium perovskite solar cells have been fabricated with an alkali carbonate-doped zinc oxide layer. 相似文献
13.
A void-free metal halide perovskite (MHP) layer on a mesoscopic TiO2 (m-TiO2) film was formed via the wetting-induced infiltration of MHP solution in the m-TiO2 film via a green ultrasonic spray coating process using a non-hazardous solvent. The systematic investigation of the behavior of ultrasonic-sprayed MHP micro-drops on the m-TiO2 film disclosed that the void-free MHP layer on the m-TiO2 film can be formed if the following conditions are satisfied: (1) the sprayed micro-drops are merged and wetted in the mesoscopic scaffold of the m-TiO2 film, (2) the MHP solution infiltrated into the m-TiO2 film by wetting is leveled to make a smooth wet MHP film, and (3) the smooth wet MHP film is promptly heat treated to eliminate dewetting and the coffee ring effect by convective flow in order to form a uniform void-free MHP layer. A void-free MHP layer on the m-TiO2 film was formed under optimal ultrasonic spray coating conditions of substrate temperature of ∼30 °C, spray flow rate of ∼11 mL h−1, nozzle to substrate distance of ∼8 cm, and MHP solution-concentration of ∼0.6 M under a fixed scan speed of 30 mm s−1 and purged N2 carrier gas pressure of 0.02 MPa. The mesoscopic MHP solar cells with an aperture area of 0.096, 1, 25, and 100 cm2 exhibited 17.14%, 16.03%, 12.93%, and 10.67% power conversion efficiency at 1 sun condition, respectively.A void-free metal halide perovskite (MHP) layer on a mesoscopic TiO2 (m-TiO2) film was formed via the wetting-induced infiltration of MHP solution in the m-TiO2 film via a green ultrasonic spray coating process using a non-hazardous solvent. 相似文献
14.
Chemical doping is a viable tactic to improve the charge transporting properties of organic semiconductors in efficient perovskite solar cells. In this paper, we first employ the low-cost inorganic salt FeCl3 as a chemical dopant to replace the traditional expensive cobalt complex for the oxidization of 2,2′,7,7′-tetrakis(N,N-p-dimethoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD), a typical organic hole-transporter. Based on the joint measurements of electron absorption spectra, cyclic voltammetry, and the hole-only device, we reveal that FeCl3 can effectively oxidize Spiro-OMeTAD and improve the hole transporting properties of Spiro-OMeTAD. Through carefully optimizing the dopant concentration, solar cells with 80% FeCl3 doped Spiro-OMeTAD achieve over 17% power conversion efficiency based on a triple cation perovskite photoactive layer, which is comparable to that of devices with a classical cobalt complex dopant. Our work demonstrates the potential of using FeCl3 as a low-cost chemical dopant for hole-transporting materials in perovskite solar cells.We have employed low-cost FeCl3 as efficient dopant of Spiro-OMeTAD for high performance perovskite solar cells. 相似文献
15.
Zezhu Jin Yanru Guo Shuai Yuan Jia-Shang Zhao Xiao-Min Liang Yujun Qin Jian-Ping Zhang Xi-Cheng Ai 《RSC advances》2020,10(21):12289
The modification of the inorganic hole transport layer has been an efficient method for optimizing the performance of inverted perovskite solar cells. In this work, we propose a facile modification of a compact NiOx film with NiOx nanoparticles and explore the effects on the charge carrier dynamic behaviors and photovoltaic performance of inverted perovskite devices. The modification of the NiOx hole transport layer can not only enlarge the surface area and infiltration ability, but also adjust the valence band maximum to well match that of perovskite. The photoluminescence results confirm the acceleration of the charge separation and transport at the NiOx/perovskite interface. The corresponding device possesses better photovoltaic parameters than the device based on control NiOx films. Moreover, the charge carrier transport/recombination dynamics are further systematically investigated by the measurements of time-resolved photoluminescence, transient photovoltage and transient photocurrent. Consequently, the results demonstrate that proper modification of NiOx can significantly enlarge interface area and improve the hole extraction capacity, thus efficiently promoting charge separation and inhibiting charge recombination, which leads to the enhancement of the device performances.The NiOx layer modified with NiOx nanoparticles obtains surface property optimization and energy level modulation, thus improving charge transport and device performance. 相似文献
16.
Itaru Raifuku Yasuaki Ishikawa Yu-Hsien Chiang Pei-Ying Lin Ming-Hsien Li Yukiharu Uraoka Peter Chen 《RSC advances》2019,9(56):32833
Perovskite solar cells have attracted much attention as next-generation solar cells because of their high efficiency and low fabrication costs. Moreover, perovskite solar cells are a promising candidate for indoor energy harvesting. We investigated the effect of bandgap tuning on the characteristics of triple cation-based perovskite solar cells under fluorescent lamp illumination. According to the current density–voltage curves, perovskite solar cells with a wider bandgap than the conventional one exhibited improved open-circuit voltage without sacrificing short-circuit current density under fluorescent lamp illumination. Moreover, the wider bandgap perovskite films including a large amount of bromine in the composition did not show phase segregation, which can degrade the photovoltaic performance of perovskite solar cells, after fluorescent lamp illumination. Our results demonstrate the facile strategy to improve the performance of perovskite solar cells under ambient lighting and great potential of perovskite solar cells for indoor applications such as power sources for the internet of things.Heavily Br-doped PSCs have a segregation-free effect in low-illuminance conditions, leading to the highest performances. 相似文献
17.
Honglin Lu Jia Zhuang Zhu Ma Weiya Zhou Haoran Xia Zheng Xiao Hua Zhang Haimin Li 《RSC advances》2019,9(2):1075
Efficient electron transport layers (ETLs) are the crucial issue for electron transport and hole blocking in organic–inorganic hybrid perovskite solar cells (PSCs). To date, most of the reported effective ETLs have comprised TiO2, which exhibits limited electron mobility and numerous defect states and restricts the enhancement of the performance of PSCs. Hence, the investigation of effective tactics for improving the electronic properties of TiO2 is critical for the fabrication of high-efficiency devices. In this study, a cerium doping method was adopted in mesoporous TiO2, which was prepared via a traditional one-step hydrothermal process, to improve its electron transport properties by recombining nanocrystals and optimizing the negative flat band potential of TiO2. Continuous, aligned and regulated recombined crystals of mesoporous TiO2 were obtained with optimized pathways of electron transport from the ETL to the FTO layer. Moreover, a small amount of Ti4+ ions was replaced by Ce4+ ions in the TiO2 lattice, which led to deformation of the TiO2 lattice and influenced the growth process of TiO2 grains. With an optimized mole proportion of Ce element in the TiO2 precursor, the power conversion efficiency (PCE) of perovskite solar cells was typically boosted to 17.75% in comparison with 15.92% in the case of undoped TiO2. J–V curves of PSCs based on TiO2 and 2% Ce-TiO2 ETLs. 相似文献
18.
The recent progress in graphene (Gr)/silicon (Si) Schottky barrier solar cells (SBSC) has shown the potential to produce low cost and high efficiency solar cells. Among the different approaches to improve the performance of Gr/Si SBSC is engineering the interface with an interfacial layer to reduce the high recombination at the graphene (Gr)/silicon (Si) interface and facilitate the transport of photo-generated carriers. Herein, we demonstrate improved performance of Gr/Si SBSC by engineering the interface with an aluminum oxide (Al2O3) layer grown by atomic layer deposition (ALD). With the introduction of an Al2O3 interfacial layer, the Schottky barrier height is increased from 0.843 V to 0.912 V which contributed to an increase in the open circuit voltage from 0.45 V to 0.48 V. The power conversion efficiency improved from 7.2% to 8.7% with the Al2O3 interfacial layer. The stability of the Gr/Al2O3/Si devices was further investigated and the results have shown a stable performance after four weeks of operation. The findings of this work underpin the potential of using an Al2O3 interfacial layer to enhance the performance and stability of Gr/Si SBSC.One approach to improve Gr/Si SBSC performance is engineering the interface with an interfacial layer. We demonstrate the improved performance of Gr/Si SBSC upon engineering the interface with an aluminium oxide (Al2O3) layer grown by atomic layer deposition (ALD).. 相似文献
19.
High-performance planar heterojunction (PHJ) perovskite solar cells (PrSCs) with MAPbI3 perovskite films were fabricated using a facile, environmentally benign, efficient and low-cost dip-coating deposition approach on a bilayered ZnO/TiO2 electron transport system from aqueous non-halide Pb(NO3)2. Outstanding performance of PrSCs was achieved due to the PHJ configuration of FTO/TiO2/ZnO/MAPbI3/spiro-OMeTAD/MoO3/Ag. These PHJ PrSCs exhibited better performance and stability with thinner ZnO layers in contrast to those with mesoporous TiO2 scaffolds, indicating that the thickness of the ZnO layer in the PHJ architecture significantly affected the surface coverage, morphology, crystallinity, and stability of the MAPbI3 perovskite films processed by dip-coating deposition.High-performance PHJ MAPbI3 perovskite films fabricated using efficient and low-cost dip-coating deposition approach over ZnO/TiO2 bilayered ETL system from an aqueous non-halide Pb(NO3)2. 相似文献
20.
Degradation of perovskite material under UV light is a problem hampering the practical application of perovskite solar cells (PSCs) despite attaining high efficiency. This paper studies the application of a luminescent down shifting (LDS) layer containing graphene quantum dots (GQDs) on top of a PSC as an efficient strategy to improve the stability and light harvesting efficiency of PSCs under UV light. With absorption and emission bands in the UV and visible regions respectively, and simple synthesis of GQDs with a high luminescence quantum efficiency (QE), GQDs are a suitable candidate as a down shifting material in the LDS layer. Here, a simple optical model is used to investigate the effect of parameters such as the concentration of GQDs, LDS layer thickness, absorption/emission bands of GQDs and the luminescence quantum efficiency on the performance of the LDS layer. The calculated results show that application of a GQD-filled LDS layer, with 94% QE and negligible RO and PA, on a PSC causes a remarkable enhancement in the incident photon to current conversion efficiency (IPCE) and thereby the short circuit current density (JSC) in the 300–400 nm spectral range of more than 400%. This strategy is also very effective in improving the stability of the PSC by suppressing the UV light from entering the device.Optical modeling of a GQD-filled LDS layer on top of a perovskite solar cell (PSC) confirms GQDs as a suitable candidate as a luminescent material for application of the LDS strategy in PSCs. 相似文献