Colloidal CdxZn1−xS nanocrystals as efficient photocatalysts for H2 production under visible-light irradiation

Cd_xZn_1−xS nanocrystals with sizes ranging from 3–11 nm were synthesized by a simple organic solution method. The nanocrystals possess a cubic zinc-blende structure and the bandgap blue-shifts from 2.1 eV to 3.4 eV by increasing the composition of Zn ions in the solid solutions. After a facile ligand exchange process, the photocatalytic activity for H₂ production of the Cd_xZn_1−xS nanocrystals was investigated under visible-light irradiation (λ ≥ 420 nm) with Na₂SO₃/Na₂S as the electron donor. It was found that the Cd_0.8Zn_0.2S had the highest photoactivity with H₂ evolution rate of 6.32 mmol g⁻¹ h⁻¹. By in situ adding Pt precursors into the reaction solution, inhomogenous Pt–Cd_xZn_1−xS nanoheterostructures were formed, which accounted for a 30% enhancement for the H₂ evolution rate comparing with that of pure Cd_0.8Zn_0.2S nanocrystals. This work highlights the use of facile organic synthesis in combination with suitable surface modification to enhance the activity of the photocatalysts.

Colloidal Cd_xZn_1−xS and Pt–Cd_xZn_1−xS nanocrystals by simple organic solution method show efficient photocatalytic H₂-evolution performance.     

Facile preparation of ZnxCd1−xS/ZnS heterostructures with enhanced photocatalytic hydrogen evolution under visible light

Hydrogen evolution from water using solar energy is regarded as a most promising process, thus, exploring efficient photocatalysts for water splitting is highly desirable. To avoid the rapid recombination of photogenerated electrons and holes in CdZnS semiconductors, Zn_xCd_1−xS/ZnS composites were synthesized via a one-step hydrothermal method and then annealed at 400 °C for 60 min under argon flow. Zn_xCd_1−xS/ZnS composites are composed of ZnS nanosheets decorated with Zn_xCd_1−xS nanorods, and TEM and UV-vis absorption spectra confirm the formation of the heterostructure between Zn_xCd_1−xS nanorods and ZnS nanosheets. Because of the well-matched band alignment, stronger optical absorption and larger carrier density, Zn_0.2Cd_0.8S/ZnS has the highest hydrogen production, with a photocatalytic hydrogen production rate up to 16.7 mmol g⁻¹ h⁻¹ under visible light irradiation. Moreover, the photocatalyst also exhibits high stability and good reusability for hydrogen production reaction. The facile and efficient approach for ZnS based heterostructures could be extended to other metal compound materials.

Schematic illustration for electron charge transfer and H₂ evolution mechanism for the Zn_0.2Cd_0.8S/ZnS nanocomposites.     

Correction: Unveiling concentration effects on the structural and optoelectronic characteristics of Zn1−xCdxS (x = 0, 0.25, 0.50, 0.75, 1) cubic semiconductors: a theoretical study

Correction for ‘Unveiling concentration effects on the structural and optoelectronic characteristics of Zn_1−xCd_xS (x = 0, 0.25, 0.50, 0.75, 1) cubic semiconductors: a theoretical study’ by Muhammad Aamir Iqbal et al., RSC Adv., 2022, 12, 22783–22791, https://doi.org/10.1039/D2RA03850A.

The authors regret that incorrect details were given for ref. 4 in the original article. The correct version of ref. 4 is given below.M. A. Iqbal, M. Malik, W. Shahid, S. Irfan, A. C. Alguno, K. Morsy, R. Y. Capangpangan, P. V. Pham and J. R. Choi, Ab-initio study of pressure influenced elastic, mechanical and optoelectronic properties of Cd_0.25Zn_0.75Se alloy for space photovoltaics. Sci. Rep., 2022, 12, 12978.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.     

Composite photocatalysts based on Cd1−xZnxS and TiO2 for hydrogen production under visible light: effect of platinum co-catalyst location

Ternary composite photocatalysts based on titania and solid solutions of CdS and ZnS were prepared and studied by a set of physicochemical methods including XRD, XPS, HRTEM, UV-vis spectroscopy, and electrochemical tests. Two synthetic techniques of platinization of Cd_1−xZn_xS/TiO₂ were compared. In the first case, platinum was deposited on the surface of synthesized Cd_1−xZn_xS (x = 0.2–0.3)/TiO₂ P25; in the second one, Cd_1−xZn_xS (x = 0.2–0.3) was deposited on the surface of Pt/TiO₂ P25. The photocatalytic properties of the obtained samples were compared in the hydrogen evolution from TEOA aqueous solution under visible light (λ = 425 nm). The Cd_1−xZn_xS (10–50 wt%; x = 0.2–0.3)/Pt (1 wt%)/TiO₂ photocatalysts demonstrated much higher photocatalytic activity than the Pt (1 wt%)/Cd_1−xZn_xS (10–50 wt%; x = 0.2–0.3)/TiO₂ ones. It turned out that the arrangement of platinum nanoparticles precisely on the titanium dioxide surface in a composite photocatalyst makes it possible to achieve efficient charge separation according to the type II heterojunctions and, accordingly, a high rate of hydrogen formation. The highest photocatalytic activity was demonstrated by 20% Cd_0.8Zn_0.2S/1% Pt/TiO₂ in the amount of 26 mmol g⁻¹ h⁻¹ (apparent quantum efficiency was 7.7%) that exceeds recently published values for this class of photocatalysts.

The determination of the preferred location of platinum particles in TiO₂–Cd_1−xZn_xS systems was carried out for the first time.     

Influence of precursor ratio and dopant concentration on the structure and optical properties of Cu-doped ZnCdSe-alloyed quantum dots

Tunable copper doped Zn_1−xCd_xS alloy quantum dots (QDs) were successfully synthesized by the wet chemical method. A one-step method is developed to synthesize doped ternary QDs which is more preferable than a two-step method. The influence of experimental parameters like the Zn/Cd ratio and Cu dopant concentration has been investigated using various spectroscopic techniques like UV-visible, photoluminescence, X-ray diffraction and Raman spectroscopy. The absorption and emission properties can be tuned by changing the concentration of components of the ternary QDs. The high concentration of dopant completely quenched the emission of the ternary QDs. EDX gives confirmation of the elemental composition of the synthesized samples. The obtained results suggest the successful doping of the ternary QDs. Interestingly, the study results revealed that the crystal structure (ZB and/or WZ) and the dual emission of the Cu-doped Zn_1−xCd_xSe alloy QDs could be controlled by varying the dopant concentration and chemical composition of the host. Doping also leads to enhancement in emission properties and provides more stability to ternary QDs. The enhancement in the photoluminescence (PL) decay lifetime of Cu-doped ternary QDs can be advantageous for optoelectronic and biosensor applications.

Tunable copper doped Zn_1−xCd_xS alloy quantum dots (QDs) were successfully synthesized by the wet chemical method.     

A ternary SnS1.26Se0.76 alloy for flexible broadband photodetectors

Layered two-dimensional (2D) materials often display unique functionalities for flexible 2D optoelectronic device applications involving natural flexibility and tunable bandgap by bandgap engineering. Composition manipulation by alloying of these 2D materials represents an effective way in fulfilling bandgap engineering, which is particularly true for SnS_2xSe_2(1−x) alloys showing a continuous bandgap modulation from 2.1 eV for SnS₂ to 1.0 eV for SnSe₂. Here, we report that a ternary SnS_1.26Se_0.76 alloy nanosheet can serve as an efficient flexible photodetector, possessing excellent mechanical durability, reproducibility, and high photosensitivity. The photodetectors show a broad spectrum detection ranging from visible to near infrared (NIR) light. These findings demonstrate that the ternary SnS_1.26Se_0.76 alloy can act as a promising 2D material for flexible and wearable optoelectronic devices.

Bandgap engineering of a ternary SnS_1.26Se_0.76 alloy for flexible broadband photodetectors.     

Quick extracellular biosynthesis of low-cadmium ZnxCd1−xS quantum dots with full-visible-region tuneable high fluorescence and its application potential assessment in cell imaging

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields. In the arena of chemical routes, however, biosynthesis has long been criticized for its low productivity, time-consuming process, and poor control over size, shape and crystallinity, keeping the much-needed technology away from practical application. In this work, a rapid and extracellular biosynthesis of multi-colour ternary Zn_xCd_1−xS QDs by a mixed sulfate-reducing bacteria (SRB)-derived supernatant was carried out for the first time to solve the problems plaguing this field of biosynthesis. The results showed that about 3.5 g L⁻¹ of Zn_xCd_1−xS QDs with size of 3.50–4.64 nm were achieved within 30 minutes. The PL emission wavelength of Zn_xCd_1−xS QDs increased from 450 to 590 nm to yield multicolor QDs by altering the molar ratio of Cd²⁺ to Zn²⁺. The SRB-biogenic Zn_xCd_1−xS QDs have high stability in gastric acid and at high temperature, as well as excellent biocompatibility and biosafety, successfully entering growing HeLa cells and labelling them without detectable harm to cells. The SRB-secreted peculiar extracellular proteins (EPs) play a decisive function in the time-saving, high-yield biosynthesis of PL-tuned multicolor QDs, which cover an abnormally high concentration of acidic amino acids to provide tremendous negatively charged sites for the absorption of Cd²⁺/Zn²⁺ for rapid nucleation and biosynthesis. The strongly electrostatic connection between the QDs and the EPs and the increasing amount of EPs attached to the QDs in response to the increase of Cd²⁺ concentration account for their high stability and excellent biocompatibility.

The biosynthesis of metal nanoparticles/QDs has been universally recognized as environmentally sound and energy-saving, generating less pollution and having good biocompatibility, which is most needed in biological and medical fields.     

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.     

Indirect-to-direct band gap transition and optical properties of metal alloys of Cs2Te1−xTixI6: a theoretical study

In recent years, double perovskites have attracted considerable attention as potential candidates for photovoltaic applications. However, most double perovskites are not suitable for single-junction solar cells due to their large band gaps (over 2.0 eV). In the present study, we have investigated the structural, mechanical, electronic and optical properties of the Cs₂Te_1−xTi_xI₆ solid solutions using first-principles calculations based on density functional theory. These compounds exhibit good structural stability compared to CH₃NH₃PbI₃. The results suggest that Cs₂TeI₆ is an indirect band gap semiconductor, and it can become a direct band gap semiconductor with the value of 1.09 eV when the doping concentration of Ti⁴⁺ is 0.50. Moreover, an ideal direct band gap of 1.31 eV is obtained for Cs₂Te_0.75Ti_0.25I₆. The calculated results indicate that all the structures are ductile materials except for Cs₂Te_0.50Ti_0.50I₆. Our results also show that these materials possess large absorption coefficients in the visible light region. Our work can provide a route to explore stable, environmentally friendly and high-efficiency light absorbers for use in optoelectronic applications.

In recent years, double perovskites have attracted considerable attention as potential candidates for photovoltaic applications.     

Stability and fundamental properties of CuxO1−x as optoelectronic functional materials

Binary Cu_xO_1−x compounds have some advantages as optoelectronic functional materials, but their further development has encountered some bottlenecks, such as inaccurate bandgap values and slow improvement of photoelectric conversion efficiency. In this work, all possible stoichiometric ratios and crystal structures of binary Cu_xO_1−x compounds were comprehensively analyzed based on a high-throughput computing database. Stable and metastable phases with different stoichiometric ratios were obtained. Their stability in different chemical environments was further analyzed according to the component phase diagram and chemical potential phase diagram. The calculation results show that Cu, Cu₂O and CuO have obvious advantages in thermodynamics. The comparison and analysis of crystal microstructure show that the stable phase of Cu_xO_1−x compounds contains the following two motifs: planar square with Cu atoms as the center and four O atoms as the vertices; regular tetrahedron with O atoms as the center and four Cu atoms as the vertices. In different stoichiometric ratio regions, the electron transfer and interaction modes between Cu and O atoms are different. This effect causes energy differences between bonding and antibonding states, resulting in the different conductivity of binary Cu_xO_1−x compounds: semi-metallic ferromagnetic, semiconducting, and metallicity. This is the root of the inconsistent and inaccurate bandgap values of Cu_xO_1−x compounds. These compositional, structural, and property variations provide greater freedom and scope for the development of binary Cu_xO_1−x compounds as optoelectronic functional materials.

The temperature and oxygen partial pressure leads binary Cu_xO_1−x compounds to have different stoichiometric ratios, resulting in different fundamental physical properties for optoelectronic functional applications.     

Room temperature synthesis of BiOBr1−xIx thin films with tunable structure and conductivity type for enhanced photoelectric performance

The surface states of semiconductors determine the semiconductor type. Although BiOCI, BiOBr and BiOI all belong to the bismuth oxyhalide semiconductor family and have similar crystal structures and electronic structures, they exhibit different conductivity types due to their respective surface states. In this paper, a modified successive ionic layer adsorption and reaction (SILAR) method was developed to fabricate I-doped BiOBr_1−xI_x nanosheet array films on FTO substrates at room temperature for the first time. Interestingly, the properties of p-type BiOBr were changed by doping an appropriate amount of iodine into a BiOBr film to form an n-type BiOBr_1−xI_x thin film. The I-doped BiOBr_1−xI_x (x = 0.2, 0.4, 0.5) nanosheet arrays had a perfect single-crystal structure, and the dominant growth plane was (110). A higher doping amount of I led to a darker colour of the BiOBr_1−xI_x film and a redshift of the absorption wavelength; consequently, the bandgap value changed from 2.80 eV to 1.85 eV. The highest short-circuit current and open-circuit voltage of the solar cell based on BiOBr_0.5I_0.5 film could reach 1.73 mA cm⁻² and 0.55 V, which was considered to be attributed to the effective light absorbance, long photogenerated charge lifetime and sufficient charge separation in the BiOBr_0.5I_0.5 film.

The significantly improved photoelectric conversion performance of the BiOBr_1−xI_0.5x film is due to the more efficient photoinduced carrier separation and transfer, longer carrier lifetime and stronger absorption in the visible light region.     

First principles study on structural,electronic and optical properties of HfS2(1−x)Se2x and ZrS2(1−x)Se2x ternary alloys

Alloying 2D transition metal dichalcogenides (TMDs) with dopants to achieve ternary alloys is as an efficient and scalable solution for tuning the electronic and optical properties of two-dimensional materials. This study provides a comprehensive study on the electronic and optical properties of ternary HfS_2(1−x)Se_2(x) and ZrS_2(1−x)Se_2(x) [0 ≤ x ≤ 1] alloys, by employing density functional theory calculations along with random phase approximation. Phonon dispersions were also obtained by using density functional perturbation theory. The results indicate that both of the studied ternary families are stable and the increase of Selenium concentration in HfS_2(1−x)Se_2(x) and ZrS_2(1−x)Se_2(x) alloys results in a linear decrease of the electronic bandgap from 2.15 (ev) to 1.40 (ev) for HfS_2(1−x)Se_2(x) and 1.94 (ev) to 1.23 (ev) for ZrS_2(1−x)Se_2(x) based on the HSE06 functional. Increasing the Se concentration in the ternary alloys results in a red shift of the optical absorption spectra such that the main absorption peaks of HfS_2(1−x)Se_2(x) and ZrS_2(1−x)Se_2(x) cover a broad visible range from 3.153 to 2.607 eV and 2.405 to 1.908 eV, respectively. The studied materials appear to be excellent base materials for tunable electronic and optoelectronic devices in the visible range.

Adding Selenium to HfS₂ and ZrS₂ two-dimensional materials allows tuning the optical properties in a wide visible spectrum that can be used in various electronic and optical applications, including solar cells.     

Synthesis of ternary oxide Zn2GeO4 nanowire networks and their deep ultraviolet detection properties

Ternary oxide Zn₂GeO₄ with a wide bandgap of 4.84 eV, as a candidate for fourth generation semiconductors, has attracted a great deal of attention for deep ultraviolet (DUV) photodetector applications, because it is expected to be blind to the UV-A/B band (290–400 nm) and only responsive to the UV-C band (200–290 nm). Here, we report on the synthesis of Zn₂GeO₄ nanowire (NW) networks by lower pressure chemical vapor deposition and investigate their corresponding DUV detection properties. We find that pure Zn₂GeO₄ NWs could be obtained at a growth pressure of 1 kPa. The DUV detection tests reveal that growth pressure exerts a significant effect on DUV detection performance. The Zn₂GeO₄ NW networks produced under 1 kPa show an excellent solar-blind photoresponsivity with fast rise and decay times (t_rise ≈ 0.17 s and t_decay ≈ 0.14 s).

Ternary oxide Zn₂GeO₄ with a wide bandgap of 4.84 eV, as a candidate for fourth generation semiconductors, has attracted lots of attention for deep UV photodetector applications, as it is blind to the UV-A/B band and only responds to the UV-C band.     

Electronic,mechanical and piezoelectric properties of glass-like complex Na2Si1−xGexO3 (x = 0.0, 0.25, 0.50, 0.75, 1.0)

Motivated by our previous work on pristine Na₂SiO₃, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na₂Si_1−xGe_xO₃ (x = 0.0, 0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT). Interestingly, the optimized bond lengths and bond angles of Na₂SiO₃ and Na₂GeO₃ resemble each other with high similarity. On doping we report the negative formation energy and feasibility of transition of Na₂SiO₃ → Na₂GeO₃ while the structural symmetry is preserved. Analyzing the electronic profile, we have observed a reduced band gap on increasing x = Ge concentration at Si-sites. All the systems are indirect band gap (Z–Γ) semiconductors. The studied systems have shown mechanical stabilities by satisfying the Born criteria for mechanical stability. The calculated results have shown highly anisotropic behaviour and high melting temperature, which are a signature of glass materials. The piezoelectric tensor (both direct and converse) is computed. The results thus obtained predict that the systems under investigation are potential piezoelectric materials for energy harvesting.

Motivated by our previous work on pristine Na₂SiO₃, we proceeded with calculations on the structural, electronic, mechanical and piezoelectric properties of complex glass-like Na₂Si_1−xGe_xO₃ (x = 0.0, 0.25, 0.50, 0.75, 1.0) by using density functional theory (DFT).     

Structural,optical and dielectric properties of tellurium-based double perovskite Sr2Ni1−xZnxTeO6

In this paper, Sr₂Ni_1−xZn_xTeO₆ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated. The Rietveld refinement of X-ray diffraction data shows that all compounds were crystallised in monoclinic symmetry with the I2/m space group. Morphological scanning electron microscopy reported that the grain sizes decreased as the dopant increased. The UV-vis diffuse reflectance spectroscopy conducted for all samples found that the optical band gap energy, E_g, increased from 3.71 eV to 4.14 eV. The dielectric permittivity ε′ values increased for the highest Zn-doped composition, Sr₂Ni_0.2Zn_0.8TeO₆, being ∼1000 and ∼60 in the low- and high-frequency range, respectively. All samples exhibited low dielectric loss (tan δ ≤ 0.20) in the range of 10⁴–10⁵ Hz frequency. Impedance measurement revealed that grain resistance decreased with enhancement in Zn content in the Sr₂NiTeO₆ crystal lattice.

In this paper, Sr₂Ni_1−xZn_xTeO₆ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated.     

Improving the optical and thermoelectric properties of Cs2InAgCl6 with heavy substitutional doping: a DFT insight

The next-generation indium-based lead-free halide material Cs₂InAgCl₆ is promising for photovoltaic applications due to its good air stability and non-toxic behavior. However, its wide bandgap (>3 eV) is not suitable for the solar spectrum and hence reduces its photoelectronic efficiency for device applications. Here we report a significant bandgap reduction from 2.85 eV to 0.65 eV via substitutional doping and its effects on the optoelectronic and opto-thermoelectric properties from a first-principles study. The results predict that Sn/Pb and Ga and Cu co-doping will enhance the density of states significantly near the valence band maximum (VBM) and thus reduce the bandgap via shifting the VBM upward, while alkali metals (K/Rb) slightly increase the bandgap. A strong absorption peak near the Shockley–Queisser limit is observed in the co-doped case, while in the Sn/Pb-doped case, we notice a peak in the middle of the visible region of the solar spectrum. The nature of the bandgap is indirect with Cu–Ga/Pb/Sn doping, and a significant reduction in the bandgap, from 2.85 eV to 0.65 eV, is observed in the case of Ga–Cu co-doping. We observe a significant increase in the power factor (PF) (2.03 mW m⁻¹ K⁻²) for the n-type carrier after Pb-doping, which is ∼3.5 times higher than in the pristine case (0.6 mW m ⁻¹ K⁻²) at 500 K.

The next-generation indium-based lead-free halide material Cs₂InAgCl₆ is promising for photovoltaic applications due to its good air stability and non-toxic behavior while it shows good thermoelectric properties when doped with Pb.     

Magnetically separable Zn1−xCo0.5xMg0.5xFe2O4 ferrites: stable and efficient sunlight-driven photocatalyst for environmental remediation

Nanomaterials have recently gained significant interest as they are believed to offer an outstanding prospect for use in environmental remediation. Among many possible candidates, due to their useful properties including magnetic nature, wide surface area, and high absorptivity, ferrite materials hold tremendous appeal, allowing them to be used for multifaceted applications. In the present study, using a sol–gel auto combustion process, a magnetically separable Zn_1−xCo_0.5xMg_0.5xFe₂O₄ (x = 0.0, 0.25, 0.50, 0.75, 1.0) ferrite with superior photocatalytic activity for dye degradation was manufactured. Rietveld refinement and FTIR studies confirm that a single-phase cubic spinel system was built for all samples with crystallite sizes of 34–57 nm. VSM has determined the magnetic properties of the samples at room temperature. With the introduction of Mg²⁺ and Co²⁺ in the Zn ferrites, a transformation from the soft superparamagnetic activity to the hard ferromagnetic character was reported. Considering the band structure in the visible region, the photocatalytic activities of the Zn_1−xCo_0.5xMg_0.5xFe₂O₄ ferrites for the degradation of the MB dye under natural sunlight were investigated. Zn_0.25Co_0.375Mg_0.375Fe₂O₄ showed an efficiency of degradation of 99.23% for MB dye with a quick 40 min irradiation period with high reusability of up to four cycles.

Nanomaterials have recently gained significant interest as they are believed to offer an outstanding prospect for use in environmental remediation.     

Synthesis of simple,low cost and benign sol–gel Cu2InxZn1−xSnS4 alloy thin films: influence of different rapid thermal annealing conditions and their photovoltaic solar cells

Cu₂In_xZn_1−xSnS₄ (x = 0.4) alloy thin films were synthesized on soda lime glass (SLG) substrate by a simple low-cost sol–gel method followed by a rapid annealing technique. The influence of sulfurization temperature and sulfurization time on the structure, morphology, optical and electrical properties of Cu₂In_xZn_1−xSnS₄ thin films was investigated in detail. The XRD and Raman results indicated that the crystalline quality of the Cu₂In_xZn_1−xSnS₄ alloy thin films was improved, accompanied by metal deficiency, particularly tin loss with increasing the sulfurization temperature and sulfurization time. From absorption spectra it is found that the band gaps of all Cu₂In_xZn_1−xSnS₄ films are smaller than that (1.5 eV) of the pure CZTS film due to In doping, and the band gap of the Cu₂In_xZn_1−xSnS₄ films can be tuned in the range of 1.38 to 1.19 eV by adjusting the sulfurization temperature and sulfurization time. Hall measurement results showed that all Cu₂In_xZn_1−xSnS₄ alloy thin films showed p-type conductivity characteristics, the hole concentration decreased and the mobility increased with the increase of sulfurization temperature and sulfurization time, which is attributed to the improvement of the crystalline quality and the reduction of grain boundaries. Finally, the Cu₂In_xZn_1−xSnS₄ film possessing the best p-type conductivity with a hole concentration of 9.06 × 10¹⁶ cm⁻³ and a mobility of 3.35 cm² V⁻¹ s⁻¹ was obtained at optimized sulfurization condition of 580 °C for 60 min. The solar cell using Cu₂In_xZn_1−xSnS₄ as the absorber obtained at the optimized sulfurization conditions of 580 °C for 60 min demonstrates a power conversion efficiency of 2.89%. We observed an increment in open circuit voltage by 90 mV. This work shows the promising role of In in overcoming the low V_oc issue in Cu-kesterite thin film solar cells.

Cu₂In_xZn_1−xSnS₄ (x = 0.4) alloy thin films were synthesized on soda lime glass (SLG) substrate by a simple low-cost sol–gel method followed by a rapid annealing technique.     

Electronic,magnetic, optical and thermoelectric properties of co-doped Sn1−2xMnxAxO2 (A = Mo,Tc): a first principles insight

The electronic, magnetic, optical and thermoelectric (TE) properties of Sn_1−2xMn_xA_xO₂ (A = Mo/Tc) have been examined using density functional theory (DFT) based on the FP-LAPW approach. The results suggested that all the doped compounds show a half-metallic ferromagnet property with a 100% spin polarization at the Fermi level within GGA and mBJ. Moreover, doping SnO₂ with double impurities reduces the bandgap. The reduced bandgaps are the result of impurity states which arise due to the Mn and Mo/Tc doping, leading to the shifts of the minima of the conduction band towards the Fermi energy caused by substantial hybridization between transition metals 3d–4d and O-2p states. Also, the (Mn, Mo) co-doped SnO₂ system exhibits a ferromagnetic ground state which may be explained by the Zener double exchange mechanism. While the mechanism that controls the ferromagnetism in the (Mn, Tc) co-doped SnO₂ system is p–d hybridization. Therefore, the role of this study is to illustrate the fact that half-metallic ferromagnet material is a good absorber of sunlight (visible range) and couples to give a combined effect of spintronics with optronics. Our analysis shows that Sn_1−2xMn_xMo_xO₂ and Sn_1−2xMn_xTc_xO₂ are more capable of absorbing sunlight in the visible range compared to pristine SnO₂. In addition, we report a significant result for the thermoelectric efficiency ZT of ∼0.114 and ∼0.11 for Sn_1−2xMn_xMo_xO₂ and Sn_1−2xMn_xTc_xO₂, respectively. Thus, the coupling of these magnetic, optical, and thermoelectric properties in (Mn, A = Mo or Tc) co-doped SnO₂ can predict that these materials are suitable for optoelectronic and thermoelectric systems.

The electronic, magnetic, optical and thermoelectric properties of Sn_1−2xMn_xA_xO₂ (A = Mo/Tc) have been examined using density functional theory (DFT) based on the FP-LAPW approach.     

Structural,elastic and optoelectronic properties of inorganic cubic FrBX3 (B = Ge,Sn; X = Cl,Br, I) perovskite: the density functional theory approach

Inorganic metal-halide cubic perovskite semiconductors have become more popular in industrial applications of photovoltaic and optoelectronic devices. Among various perovskites, lead-free materials are currently most explored due to their non-toxic effect on the environment. In this study, the structural, electronic, optical, and mechanical properties of lead-free cubic perovskite materials FrBX₃ (B = Ge, Sn; X = Cl, Br, I) are investigated through first-principles density-functional theory (DFT) calculations. These materials are found to exhibit semiconducting behavior with direct bandgap energy and mechanical phase stability. The observed variation in the bandgap is explained based on the substitutions of cations and anions sitting over B and X-sites of the FrBX₃ compounds. The high absorption coefficient, low reflectivity, and high optical conductivity make these materials suitable for photovoltaic and other optoelectronic device applications. It is observed that the material containing Ge (germanium) in the B-site has higher optical absorption and conductivity than Sn containing materials. A systematic analysis of the electronic, optical, and mechanical properties suggests that among all the perovskite materials, FrGeI₃ would be a potential candidate for optoelectronic applications. The radioactive element Fr-containing perovskite FrGeI₃ may have applications in nuclear medicine and diagnosis such as X-ray imaging technology.

Inorganic metal-halide cubic perovskite semiconductors have become more popular in industrial applications of photovoltaic and optoelectronic devices.