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First-Principles Modeling of Lead-Free Perovskites for Photovoltaic Applications

Liu, Diwen, Li, Qiaohong, Jing, Huijuan, Wu, Kechen
Journal of physical chemistry 2019 v.123 no.6 pp. 3795-3800
absorption, energy, ionization, lead, models, optical properties, solar cells, thermodynamics, toxicity
The material class of hybrid organic–inorganic halide perovskites has been rapidly progressed in the field of photovoltaic applications. However, this class of materials has limitations associated with its poor stability and toxicity of the lead element. Therefore, there is a strong desire to search for environmentally friendly perovskite materials without affecting the conversion efficiency. First-principles calculations have been employed to study thermodynamic stability, electronic, and optical properties of potential candidate lead-free perovskites. The results show that the ionization energy at the A-site can provide an explanation for the stabilities of hybrid perovskites. The bond lengths and bond angles are likely responsible for the discrepancy in the band gap. The results indicate that DAGeI₃ has better stability and suitable band gap among Ge-based AGeI₃ perovskites. It is observed that the Si-doped perovskites are energetically favorable. CsGe₂/₃Si₁/₃I₃ can become the potential candidate for the light absorption layer because of the ideal band gap among the Si-doped perovskites. Our study offers insights into how composition variation affects thermodynamic stability and electronic properties in this family of Ge-based perovskites. This work is helpful to obtain further insights into developing lead-free perovskite solar cells.