S. Seck^1,, A. Sow¹, M. S. Mané¹, A. Ndiaye¹, E. M. Keita¹, B. Ndiaye¹, B. Mbow¹, C. Sène¹

Recently, organic/inorganic hybrid perovskite materials have attracted particular interest in the research community for future generations of photovoltaic systems, due to their manufacturing process ease by solution treatment, their low cost and exceptional optoelectronic properties. Owing mainly to these superior optoelectronic properties and the long carrier lifetime in these materials, perovskite-based photovoltaic devices have achieved high conversion efficiencies up to 25%. However, the presence of lead which is very environmental and human harmful together with the stability issues of these materials constitute major problems encountered in the development of photovoltaic devices based on these materials. Faced with these problems, a large number of alternative absorber materials based on lead-free perovskites and/or inorganic perovskites are increasingly being explored. In this work, we carried out a modeling study of photovoltaic devices using the CH₃NH₃Sn_1-yGe_yI₃ lead-free perovskite as absorbing material. The ZnO(n⁺)/Cu₂O(n)/CH₃NH₃Sn_1-yGe_yI₃(p) structure is considered for this purpose in which 0≤y≤1. The evolution of the internal quantum efficiency is analyzed as a function of the relative proportion of tin and germanium in the perovskite and also as a function of various other parameters including the thickness of the base and the minority carrier diffusion length in this material. The substitution of lead by metals such as tin and/or germanium leads to lead-free perovskites having opto-electronic properties adapted to the production of high-performance photovoltaic devices. Materials of high optoelectronic and structural properties are in particular obtained for Ge content in the perovskite less than 0.50. In this range of the Ge content, our study shows that the best photovoltaic devices are obtained for values of the germanium (Ge) content close to 0.25

perovskite, photovoltaic cell, quantum efficiency, diffusion length, absorber thickness