Design and optimization of high-performance eco-friendly perovskite solar cells: Utilizing FAMASnGeI3 and CsGeI3 as absorbers and tuning HTL and interface parameters

In this work, several designs of lead-based and lead-free perovskite solar cells (PSCs) have been developed and investigated. For the proposed designs, CH₃NH₃PbI₃ (lead-based), FAMASnGeI₃, and CsGeI₃ (lead-free) are used as absorber materials, ${\mathrm{\text{Cu}}}_2\mathrm{\text{O}}$ and NiO have been used as Hole Transport Layer (HTL) materials and TiO₂ as Electron Transport Layer (ETL) materials. ETL materials, in general, have more concern with stability issues and HTL materials have more issues with efficiency improvements. The effect of changing thickness, doping density and defect density of the absorber layer, as well as HTL, defect density of absorber/HTL interface and work functions of front and back contacts on the performance of the proposed devices, are investigated. To enhance the device performance, optimization of the device parameters is performed. After optimization of different parameters, it is observed that the lead-based device structure TiO₂/CH₃NH₃PbI₃/NiO has a maximum efficiency of 29.94%. Even the corresponding lead-free device structure TiO₂/CsGeI₃/NiO exhibits a maximum efficiency of 29.19%. Additionally, this study delved into the influence of altering series and shunt resistances, as well as temperature on the operational characteristics of the lead-free optimized device. Such eco-friendly and cost-effective alternatives as lead-free perovskite cells can be very promising for future work.