Stability of perovskite solar cells: issues and prospects

Even though power conversion efficiency has already reached 25.8%, poor stability is one of the major challenges hindering the commercialization of perovskite solar cells (PSCs). Several initiatives, such as structural modification and fabrication techniques by numerous ways, have been employed by researchers around the world to achieve the desired level of stability. The goal of this review is to address the recent improvements in PSCs in terms of structural modification and fabrication procedures. Perovskite films are used to provide a broad range of stability and to lose up to 20% of their initial performance. A thorough comprehension of the effect of the fabrication process on the device''s stability is considered to be crucial in order to provide the foundation for future attempts. We summarize several commonly used fabrication techniques – spin coating, doctor blade, sequential deposition, hybrid chemical vapor, and alternating layer-by-layer. The evolution of device structure from regular to inverted, HTL free, and ETL including the changes in material utilization from organic to inorganic, as well as the perovskite material are presented in a systematic manner. We also aimed to gain insight into the functioning stability of PSCs, as well as practical information on how to increase their operational longevity through sensible device fabrication and materials processing, to promote PSC commercialization at the end.

Stability issues are the key challenges for commercialization of PSCs. Different stability issues including modification of the structural design and material, fabrication process should be considered and improved to improve the stability of PSCs.     

Recent progress in porphyrin- and phthalocyanine-containing perovskite solar cells

In this review, we summarize the application of porphyrins and phthalocyanines in perovskite solar cells to date. Since the first porphyrin- and phthalocyanine-based perovskite solar cells were reported in 2009, their power conversion efficiency has dramatically increased from 3.9% to over 20%. Porphyrins and phthalocyanines have mostly been used as the charge selective layers in these cells. In some cases, they have been used inside the perovskite photoactive layer to form two-dimensional perovskite structures. In other cases, they were used at the interface to engineer the surface energy level. This review gives a chronological introduction to the application of porphyrins and phthalocyanines for perovskite solar cells depending on their role. This review article also provides the history of porphyrin and phthalocyanine derivative development from the perspective of perovskite solar cell applications.

In this review, we summarize the application of porphyrins and phthalocyanines in perovskite solar cells to date.     

Journey of anthraquinones as anticancer agents – a systematic review of recent literature

Anthraquinones are privileged chemical scaffolds that have been used for centuries in various therapeutic applications. The anthraquinone moiety forms the core of various anticancer agents. However, the emergence of drug-resistant cancers warrants the development of new anticancer agents. The research endeavours towards new anthraquinone-based compounds are increasing rapidly in recent years. They are used as a core chemical template to achieve structural modifications, resulting in the development of new anthraquinone-based compounds as promising anticancer agents. Mechanistically, most of the anthraquinone-based compounds inhibit cancer progression by targeting essential cellular proteins. Herein, we review new anthraquinone analogues that have been developed in recent years as anticancer agents. This includes a systematic review of the recent literature (2005–2021) on anthraquinone-based compounds in cell-based models and key target proteins such as kinases, topoisomerases, telomerases, matrix metalloproteinases and G-quadruplexes involved in the viability of cancer cells. In addition to this, the developments in PEG-based delivery of anthraquinones and the toxicity aspects of anthraquinone derivatives are also discussed. The review dispenses a compact background knowledge to understanding anthraquinones for future research on the expansion of anticancer therapeutics.

Anthraquinones are privileged chemical motifs with diverse therapeutic applications, especially in the treatment of cancer. The extensive literature highlights the significance of anthraquinones as potent anticancer agents.     

Theoretical study of D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives as sensitizers for dye-sensitized solar cells

We have designed four dyes based on D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives for dye-sensitized solar cells (DSSCs) and studied their optoelectronic properties as well as the effects of the introduction of alkoxy groups and thiophene group on these properties. The geometries, single point energy, charge population, electrostatic potential (ESP) distribution, dipole moments, frontier molecular orbitals (FMOs) and HOMO–LUMO energy gaps of the dyes were discussed to study the electronic properties of dyes based on density functional theory (DFT). And the absorption spectra, light harvesting efficiency (LHE), hole–electron distribution, charge transfer amount from HOMO to LUMO (Q_CT), D index, H_CT index, S_m index and exciton binding energy (E_coul) were discussed to investigate the optical and charge-transfer properties of dyes by time-dependent density functional theory (TD-DFT). The calculated results show that all the dyes follow the energy level matching principle and have broadened absorption bands at visible region. Besides, the introduction of alkoxy groups into triarylamine donors and thiophene groups into conjugated bridges can obviously improve the stability and optoelectronic properties of dyes. It is shown that the dye D4, which has had alkoxy groups as well as thiophene groups introduced and possesses a D–π–A′–π–A configuration, has the optimal optoelectronic properties and can be used as an ideal dye sensitizer.

We have designed four dyes based on D–A′–π–A/D–π–A′–π–A triphenylamine and quinoline derivatives for DSSCs and studied their optoelectronic properties as well as the effects of the introduction of alkoxy groups and thiophene group on the properties.     

Effect of fluorine substituents on benzothiadiazole-based D–π–A′–π–A photosensitizers for dye-sensitized solar cells

Two D–π–A′–π–A organic dyes with triazatruxene (TAT) as the electron donor, thiophene as the π-spacer, benzoic acid as the anchor group, and benzothiadiazole (BT) or difluorobenzo[c][1,2,5]thiadiazole (DFBT) as the additional acceptor, namely LS101 and LS102, respectively, were applied to dye-sensitized solar cells (DSSCs). As fluorine substituents are usually strong electron-withdrawing groups, introducing two fluorine atoms into BT was expected to strengthen the electron-withdrawing ability of the auxiliary acceptor, resulting in DSSCs with a broader light capture region and further improved power conversion efficiency (PCE). Fluorine is the smallest electron-withdrawing group with an induction effect, but can also act as an electron-donating group owing to its conjugation effect. When the conjugation effect is dominant, the electron-withdrawing ability of additional acceptor DFBT decreases instead. Accordingly, the band gap of LS102 was broadened and the UV-vis absorption spectrum was blue-shifted. In the end, DSSCs based on LS101 achieved a champion PCE of 10.2% (J_sc = 15.1 mA cm⁻², V_oc = 966 mV, FF = 70.1%) while that based on LS102 gave a PCE of only 8.6% (J_sc = 13.4 mA cm⁻², V_oc = 934 mV, FF = 69.1%) under standard AM 1.5G solar irradiation (100 mW cm⁻²) with Co²⁺/Co³⁺ as the electrolyte.

The results and interpretations can clearly explain the reasons for the poor photovoltaic performance of DFBT in DSSCs.     

Regio-regular alternating diketopyrrolopyrrole-based D1–A–D2–A terpolymers for the enhanced performance of polymer solar cells

We designed and synthesized regio-regular alternating diketopyrrolopyrrole (DPP)-based D₁–A–D₂–A terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) using a primary donor (D₁) [3,3′-difluoro-2,2′-bithiophene (F2T2)] and a secondary donor (D₂) [2,2′-bithiophene (T2), (E)-1,2-di(thiophen-2-yl)ethene (TVT), or dithieno[3,2-b:2′,3′-d]thiophene (DTT)]. A PDPP2DT-F2T2 D–A polymer was synthesized as well to compare optical, electronic, and photovoltaic properties. The absorption peaks of the terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) were longer (λ_max = 801–810 nm) than the peak of the PDPP2DT-F2T2 polymer (λ_max = 799 nm), which is associated with the high-lying HOMO levels of the terpolymers (−5.08 to −5.13 eV) compared with the level of the PDPP2DT-F2T2 polymer (−5.38 eV). The photovoltaic properties of these DPP-based polymers were investigated under simulated AM 1.5G sunlight (100 mW cm⁻²) with a conventional structure (ITO/PEDOT:PSS/polymer:PC₇₁BM/Al). The open-circuit voltages (V_oc) of photovoltaic devices containing the terpolymers were slightly lower (0.68–0.70 V) than the V_oc of the device containing the PDPP2DT-F2T2 polymer (0.79 V). The short-circuit current (J_sc) of the PDPPF2T2DPP-DTT device was significantly improved (14.14 mA cm⁻²) compared with that of the PDPP2DT-F2T2 device (8.29 mA cm⁻²). As a result, the power conversion efficiency (PCE) of the PDPPF2T2DPP-DTT device (6.35%) was increased by 33% compared with that of the simple D–A-type PDPP2DT-F2T2 device (4.78%). The highest J_sc and PCE values (the PDPPF2T2DPP-DTT device) were attributed to an optimal nanoscopically mixed morphology and strong interchain packing with a high face-on orientation in the blend film state. The study demonstrated that our strategy of using multiple donors in a regio-regular alternating fashion could fine-tune the optical, electronic, and morphological properties of D–A-type polymers, enhancing the performance of polymer solar cells.

We designed and synthesized regio-regular alternating diketopyrrolopyrrole (DPP)-based D₁–A–D₂–A terpolymers (PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT) for use in polymer solar cells.     

Scanning atmospheric-pressure plasma jet treatment of nickel oxide with peak temperature of ∼500 °C for fabricating p–i–n structure perovskite solar cells

Scanning atmospheric-pressure plasma jet (APPJ) treatment of nickel oxide with a peak temperature of 500 °C was performed for fabricating p–i–n structure perovskite solar cells (PSCs). APPJ post-treatment increases the haze of NiO on FTO glass, leading to enhanced light scattering in PSCs that in turn improves the cell efficiency. APPJ treatment on NiO also improves the wettability to facilitate the follow-up deposition of CH₃NH₃PbI₃. This also leads to better PSC performance. X-ray photoelectron spectroscopy indicates that APPJ treatment results in fewer C–N bonds and reduced NiAc₂ content, suggesting more complete conversion of the liquid precursor into NiO. With three APPJ scans, the average PCE improves from 11.91% to 13.47%, with the best-performing PSC achieving an efficiency of 15.67%.

Scanning atmospheric-pressure plasma jet (APPJ) treatment of nickel oxide with a peak temperature of 500 °C was performed for improving the performance of p–i–n structure perovskite solar cells (PSCs).     

Characterization and simulation study of organic solar cells based on donor–acceptor (D–π–A) molecular materials

In this study, the analysis of microelectronic and photonic structure in a one dimension program [AMPS-1D] has been successfully used to study organic solar cells. The program was used to optimize the performance of organic solar cells based on (carbazole-methylthiophene), benzothiadiazole and thiophene [(Cbz-Mth)-B-T]2 as electron donors, and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) as an electron acceptor. The optoelectronic properties of these dyes were investigated by using the Density Functional Theory DFT/B3LYP/6-31G(d,p) method. We studied the influence of the variation of the thickness of the active layer, the temperature, and the density of the effective states of the electrons and the holes in the conduction and valence bands respectively on the performance of the solar cells based on [(Cbz-Mth)-BT]2–PCBM as a photoactive material, sandwiched between a transparent indium tin oxide (ITO) and an aluminum (Al) electrode. The addition of other thiophene units in the copolymer or the deposition of a layer of PEDOT between the anode (ITO) and the active layer, improves the performances of the cell, especially resulting in a remarkable increase in the value of the power conversion efficiency (PCE).

The solar cell ITO/PEDOT/[(Cbz-Mth)-B-DT]2-A:PCBM/Al under study and the results obtained, including a power conversion efficiency of 11%. The impact of several parameters on the performance has been studied to obtain the optimal device architecture.     

Microfluidics for core–shell drug carrier particles – a review

Core–shell drug-carrier particles are known for their unique features. Due to the combination of superior properties not exhibited by the individual components, core–shell particles have gained a lot of interest. The structures could integrate core and shell characteristics and properties. These particles were designed for controlled drug release in the desired location. Therefore, the side effects would be minimized. So, these particles'' advantages have led to the introduction of new methods and ideas for their fabrication. In the past few years, the generation of drug carrier core–shell particles in microfluidic chips has attracted much attention. This method makes it possible to produce particles at nanometer and micrometer levels of the same shape and size; it usually costs less than other methods. The other advantages of using microfluidic techniques compared to conventional bulk methods are integration capability, reproducibility, and higher efficiency. These advantages have created a positive outlook on this approach. This review gives an overview of the various fluidic concepts that are used to generate microparticles or nanoparticles. Also, an overview of traditional and more recent microfluidic devices and their design and structure for the generation of core–shell particles is given. The unique benefits of the microfluidic technique for core–shell drug carrier particle generation are demonstrated.

Microfluidics application for core–shell drug carrier particles synthesis and the advantages of using this technique compared to conventional bulk methods.     

Totally room-temperature solution-processing method for fabricating flexible perovskite solar cells using an Nb2O5–TiO2 electron transport layer

Flexible perovskite solar cells are new technology-based products developed by the global solar industry and are promising candidates for realizing a flexible and lightweight energy supply system for wearable and portable electronic devices. A critical issue for flexible perovskite solar cells is to achieve high power conversion efficiency (PCE) while using low-temperature solution-based technology for the fabrication of a compact charge collection layer. Herein, we innovatively introduce niobium ethoxide as a precursor additive to TiO₂ NCs, which allows realization of an Nb₂O₅–TiO₂ electron transport layer (ETL). The presence of Nb₂O₅ remarkably enhances electron mobility and electrical conductivity of the ETLs. In addition, uniform perovskite films are prepared by an annealing-free solution-based method. The excellent performance of the cell is attributed to its smooth film surface and high electron mobility, and performance is verified by the effective suppressions of charge recombination and time-resolved photoluminescence. PCEs of 15.25% and 13.60% were obtained for rigid substrates (glass/fluorine-doped tin oxide) and an indium tin oxide/PET (poly(ethylene terephthalate)) flexible substrate by using a totally room-temperature solution-processing method, respectively.

Flexible perovskite solar cells are new technology-based products developed by the global solar industry and are promising candidates for realizing a flexible and lightweight energy supply system for wearable and portable electronic devices.     

Low photoactive phase temperature all-inorganic,tin–lead mixed perovskite solar cell

CsPbI₃ films have recently attracted significant attention as efficient absorbers for thermally stable photovoltaic devices. However, their large bandgap and photoactive black phase formation at high temperature impede their use for practical applications. Using the concept of lattice contraction, we demonstrate a low bandgap (≤1.44 eV) cesium-based inorganic perovskite CsPb_xSn_1−xI₃ that can be solution processed at low temperature for photovoltaic devices. The results from systematic measurements imply that the partial substitution of lead (Pb) with tin (Sn) results in crystal lattice contraction, which is essential for realizing photoactive phase formation at l00 °C and stabilizing photoactive phase at room temperature. These findings demonstrate the potential of using cesium-based inorganic perovskite as viable alternatives to MA- or FA-based perovskite photovoltaic materials.

In Cs-based all inorganic perovskite solar cells based, doping Sn can cause lattice shrinkage, which reduces annealing temperature of forming photoactive phase.     

Graphene/Si Schottky solar cells: a review of recent advances and prospects

Graphene has attracted tremendous interest due to its unique physical and chemical properties. The atomic thickness, high carrier mobility and transparency make graphene an ideal electrode material which can be applied to various optoelectronic devices such as solar cells, light-emitting diodes and photodetectors. In recent years, there has been a growing interest in developing graphene/silicon Schottky junction solar cells and the power conversion efficiency has reached up to 15.8% with an incredible speed. In this review, we introduce the structure and mechanism of graphene/silicon solar cells briefly, and then summarize several key strategies to improve the performance of the cells. Finally, the challenges and prospects of graphene/silicon solar cells are discussed in the development of the devices in detail.

The structure and mechanism of graphene/silicon solar cells, and several key strategies to improve the performance of the cells.     

Stability of organometal halide perovskite solar cells and role of HTMs: recent developments and future directions

Perovskite solar cells (PSCs) have recently emerged as one of the most exciting fields of research of our time, and the World Economic Forum in 2016 recognized them as one of the top 10 technologies in 2016. With 22.7% power conversion efficiency, PSCs are poised to revolutionize the way power is produced, stored and consumed. However, the widespread use of PSCs requires addressing the stability issue. Therefore, it is now time to focus on the critical step i.e. stability under the operating conditions for the development of a sustainable and durable PV technology based on PSCs. In order to improve the stability of PSCs, hole transport materials (HTMs) have been considered as the paramount components. This is due to the fact that most of the organic HTMs possess a hygroscopic and acidic nature that leads to poor stability of the PSCs. This article reviews briefly but comprehensively the environmental stability issues of PSCs, fundamentals, strategies for improvement, the role of HTMs towards stability and various types of HTMs. Also the environmental parameters affecting the performance of perovskite solar cells including temperature, moisture and light soaking environment have been considered.

This article gives the comprehensive review on the environmental stability issues of PSCs.     

Research progress and applications of silica-based aerogels – a bibliometric analysis

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields. In order to grasp the progress of silica-based aerogels, we utilize bibliometrics and visualization methods to analyze the research hotspots and the application of this important field. Firstly, we collect all the publications on silica-based aerogels and then analyze their research trends and performances by a bibliometric method regarding publication year/citation, country/institute, journals, and keywords. Following this, the major research hotspots of this area with a focus on synthesis, mechanical property regulation, and the applications for thermal insulation, adsorption, and Cherenkov detector radiators are identified and reviewed. Finally, current challenges and directions in the future regarding silica-based aerogels are also proposed.

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields.     

New organic dye-sensitized solar cells based on the D–A–π–A structure for efficient DSSCs: DFT/TD-DFT investigations

Global energy consumption has increased due to population growth and economic development. Solar energy is one of the most important renewable energy sources for human consumption. In this research, four novel organic dyes (D2–D5) of the D–A–π–A structure based on triphenylamine (TPA) were studied theoretically using DFT and TD-DFT techniques for future usage as dye-sensitized solar cells (DSSCs). The effects of modifying the π-spacer of the reference molecule D1 on the structural, electronic, photovoltaic, and optical characteristics of the D2–D5 dyes were studied in detail. D2–D5 exhibited band gaps (E_gap) in the range from 1.89 to 2.10 eV with λ_abs in the range of 508 to 563 nm. The results obtained show that modifying the π-spacer of the dye D1 increased its hole injection and reinforced the intramolecular charge-transfer (ICT) impact, which resulted in a red-shifted ICT absorption with a greater molar extinction coefficient. The theoretically calculated open-circuit voltage (V_oc) values ranged from 0.69 to 1.06 eV, while the light-harvesting efficiency (LHE) values varied from 0.95 to 0.99. Indeed, this theoretical research could guide chemists to synthesize effective dyes for DSSCs.

Global energy consumption has increased due to population growth and economic development.     

Alleviate the J–V hysteresis of carbon-based perovskite solar cells via introducing additional methylammonium chloride into MAPbI3 precursor

The hysteretic phenomenon commonly exists in the J–V curves of perovskite solar cells with different structures, especially for carbon-based mesoscopic perovskite solar cells without hole-conductor (carbon-based PSCs). By adding moderate amounts of methylammonium chloride (MACl) into MAPbI₃ perovskite precursor, we found the J–V hysteresis of carbon-based PSCs could be significantly alleviated and the crystallinity of MAPbI₃ perovskite could also be influenced. With the increasing amount of MACl, MAPbI₃ perovskite showed better and better crystallinity until the MACl came to 0.45 M. The champion device with 0.45 M of additional MACl exhibited a preferable PCE of 14.27% for reverse-scan (RS) and 14.50% for forward-scan (FS), significantly higher than that of the pristine device (8.74% for RS and 4.80% for FS). What''s more, the J–V hysteretic index of the device gradually decreased along with the increasing amount of MACl, and kept at low value even when the crystallinity of MAPbI₃ perovskite became poor. Through XRD and PL analysis, we demonstrated that the recombination rate of the accumulated charges at the perovskite/TiO₂ interface is the main reason for photocurrent hysteresis in carbon-based PSCs. High quality of perovskite crystals is an important contributing factor for high-performance PSCs with low hysteresis, but there is no necessary correlation between low hysteresis and good crystallinity. This research presents an effective way to fabricate carbon-based PSCs with low-hysteresis, and at the same time, provides evidence for investigating the origin of J–V hysteresis of PSCs.

The hysteretic phenomenon commonly exists in the J–V curves of perovskite solar cells with different structures, especially for carbon-based mesoscopic perovskite solar cells without hole-conductor (carbon-based PSCs).     

Bandgap adjustment assisted preparation of >18% CsyFA1−yPbIxBr3−x-based perovskite solar cells using a hybrid spraying process

The preparation of Cs_yFA_1−yPbI_xBr_3−x-based perovskite by ultrasonic spraying has valuable application in the preparation of tandem solar cells on textured substrates due to its excellent stability and the advantages of large-area uniform preparation from the spraying technology. However, the bandgap of perovskite prepared by spraying method is difficult to adjust, and perovskites with a wide bandgap have the issue of phase instability. Here, we improved the crystallinity of the perovskite by simply controlling the post-annealing temperature. The results show that perovskite film prepared by hybrid spray method has the best crystallinity and device performance at a post-annealing temperature of 170 °C. On this basis, the bandgap of perovskite was changed from 1.53 eV to 1.76 eV by controlling the ratio of the organic halogen precursor solution. When the bandgap is 1.57 eV, a perovskite solar cell with an efficiency of 18.31% is obtained.

High-efficiency perovskite solar cells with good grain morphology and adjustable band gap were prepared by ultrasonic spray.     

MAPbBr3 perovskite solar cells via a two-step deposition process

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.     

Enhancing the thermal stability of the carbon-based perovskite solar cells by using a CsxFA1−xPbBrxI3−x light absorber

Despite the impressive photovoltaic performance with a power conversion efficiency beyond 23%, perovskite solar cells (PSCs) suffer from poor long-term stability, failing by far the market requirements. Although many efforts have been made towards improving the stability of PSCs, the thermal stability of PSCs with CH₃NH₃PbI₃ as a perovskite and organic hole-transport material (HTM) remains a challenge. In this study, we employed the thermally stable (NH₂)₂CHPbI₃ (FAPbI₃) as the light absorber for the carbon-based and HTM-free PSCs, which can be fabricated by screen printing. By introducing a certain amount of CsBr (10%) into PbI₂, we obtained a phase-stable Cs_xFA_1−xPbBr_xI_3−x perovskite by a “two-step” method and improved the device power conversion efficiency from 10.81% to 14.14%. Moreover, the as-prepared PSCs with mixed-cation perovskite showed an excellent long-term stability under constant heat (85 °C) and thermal cycling (−30 °C to 85 °C) conditions. These thermally stable and fully-printable PSCs would be of great significance for the development of low-cost photovoltaics.

Mixed-cation Cs_xFA_1–xPbBr_xI_3–x perovskite was used as light absorber for the carbon-based perovskite solar cells, and the as-prepared solar devices showed excellent long-term stability under constant heat (85 °C) and thermal cycling (−30 °C to 85 °C) condition.     

Enhanced crystallinity of CH3NH3PbI3 by the pre-coordination of PbI2–DMSO powders for highly reproducible and efficient planar heterojunction perovskite solar cells

Solution processable CH₃NH₃PbI₃ has received considerable attention for highly-efficient perovskite solar cells. However, the different solubility of PbI₂ and CH₃NH₃I is problematic, initiating active solvent engineering research using dimethyl sulfoxide (DMSO). Here we investigated the pre-coordination of PbI₂–DMSO powders for planar heterojunction perovskite solar cells fabricated by a low-temperature process (≤100 °C). Pre-coordination was carried out by simple mechanical mixing using a mortar and pestle. The composition of PbI₂–DMSO_x (x = 0, 1, or 2) in the powder mixture was investigated by gradually increasing mechanical mixing time, and a dominant composition of PbI₂–DMSO₁ was obtained after a 10 min mixing process. The pre-coordinated PbI₂–DMSO powders were then blended with CH₃NH₃I in DMF to make the CH₃NH₃PbI₃ film by toluene-assisted spin-coating and heat treatment. Compared with the one-step blending of CH₃NH₃I, PbI₂, and DMSO in DMF, the pre-coordination method resulted in better dissolution of PbI₂, larger grain size, and pinhole-free morphology. Consequently, absorption, fluorescence, carrier lifetime, and charge extraction were enhanced. The average open-circuit voltage (1.046 V), short-circuit current (22.9 mA cm⁻²), fill factor (73.5%), and power conversion efficiency (17.6%) were increased by 2–12% with decreased standard deviations (13–50%), compared with the one-step blending method. The best efficiency was 18.2%. The simple mechanical pre-coordination of PbI₂–DMSO powders was very effective in enhancing the crystallinity of CH₃NH₃PbI₃ and photovoltaic performance.

The pre-coordinated PbI₂–DMSO powders improved efficiency and reproducibility of perovskite solar cells with enhanced crystallinity of the CH₃NH₃PbI₃ film.