Lead (Pb) free non-toxic perovskite solar cells have become more important in the commercialization of the photovoltaic devices. In this study the structural, electronic, optical and mechanical properties of Pb-free inorganic metal halide cubic perovskites CsBX₃ (B = Sn, Ge; X = I, Br, Cl) for perovskite solar cells are simulated using first-principles Density Functional Theory (DFT). These compounds are semiconductors with direct band gap energy and mechanically stable. Results suggest that the materials have high absorption coefficient, low reflectivity and high optical conductivity with potential application in solar cells and other optoelectronic energy devices. On the basis of the optical properties, one can expect that the Germanium (Ge) would be a better replacement of Pb as Ge containing compounds have higher optical absorption and optical conductivity than that of Pb containing compounds. A combinational analysis of the electronic, optical and mechanical properties of the compounds suggests that CsGeI₃ based perovskite is the best Pb-free inorganic metal halide semiconductor for the solar cell application. However, the compound with solid solution of CsGe(I_0.7Br_0.3)₃ is found to be mechanically more ductile than CsGeI₃. This study will also guide to obtain Pb-free organic perovskites for optoelectronic devices.

Methylammonium bismuth (III) iodide single crystals and films have been developed and investigated. We have further presented the first demonstration of using this organic–inorganic bismuth-based material to replace lead/tin-based perovskite materials in solution-processable solar cells. The organic–inorganic bismuth-based material has advantages of non-toxicity, ambient stability, and low-temperature solution-processability, which provides a promising solution to address the toxicity and stability challenges in organolead- and organotin-based perovskite solar cells. We also demonstrated that trivalent metal cation-based organic–inorganic hybrid materials can exhibit photovoltaic effect, which may inspire more research work on developing and applying organic-inorganic hybrid materials beyond divalent metal cations (Pb (II) and Sn (II)) for solar energy applications.

Developing of lead-free double perovskites have drawn significant interest for photovoltaics and optoelectronics as the materials have the potential to avoid toxicity and instability issues associated with lead-based organometallic perovskites. In this study, we report the optoelectronic properties of a new group of non-toxic lead-free organic-inorganic halide double perovskites composed of caesium (Cs), methylammonium (MA) or formamidinium (FA) with bismuth (Bi) and metal copper (Cu). We perform density functional theory investigations to calculate the structural, electronic and optical properties of 18 Pb-free compounds, ABiCuX₆ [A = Cs₂, (MA)₂, (FA)₂, CsMA, CsFA, MAFA; X = I, Br, Cl] to predict their suitability in photovoltaic and optoelectronic applications. We found that the considered compounds are semiconductors with a tunable band gap characteristics that are suitable for some devices like light emitting diodes. In addition to this, the high dielectric constant, high absorption, high optical conductivity and low reflectivity suggest that the materials have the potential in a wide range of optoelectronic applications including solar cells. Furthermore, we predict that the organic-inorganic hybrid double perovskite (FA)₂BiCuI₆ is the best candidate in photovoltaic and optoelectronic applications as the material has superior optical and electronic properties.

In this review, we report the recent research progress in the area of design and synthesis of tin sulfide and selenide (SnS, SnS ₂ , SnSe, and SnSe ₂ ) based anode materials for Li-ion batteries and Na-ion batteries.