Theoretical analysis of all-inorganic solar cells based on numerical simulation of CsGeI3/CsPbI3 with p-p+ built-in electric field

With the development of perovskite solar cells (PSCs) technology, inorganic perovskite led by CsPbI3 gradually shows the photovoltaic performance of organic perovskite cells. However, this is still based on the organic charge transport layer. CsPbI3 with all-inorganic structure still need to be further studied. Therefore, in this study, an all inorganic CsGeI3/CsPbI3 laminated structure with CsGeI3 instead of organic HTL is introduced, and numerical simulation is carried out through SCAPS-1D (Solar Cells Capability Simulator). It is found that the two perovskite layers, which are both p-type materials, have shown excellent efficiency in the p-p+ built-in electric field. In this paper, PSCs are optimized with absorbing layer thickness, doping concentration, defect density, metal electrode work function and so on. The best thickness is determined according to the different light absorption properties of Pb2+ and Ge2+, and the toxicity of the original single-layer lead based perovskite is reduced. Through the comprehensive analysis of band bending, built-in electric field and recombination rate, we explained the reason why the parameters increase with the growth of doping concentration (NA). In terms of NA regulation, it is found through simulation that when NA of the two absorption layers is at 1015 to 1018 cm−3, the photogenerated carriers are driven by the strong p-p+ built-in electric field to migrate well in the flat energy band, which significantly improves the photovoltaic performance of PSCs. For the defect density the charge transport layer, the PSC absorption characteristics, and the metal electrodes, we made a choice based on the photovoltaic performance and process level. Finally, the power conversion efficiency of the optimized PSCs reached 24.06 % and the fill factor is 86.19 %. This study proved that p-p+ structure constructed by lead germanium mixed metal has great potential for inorganic perovskite solar cells with Cs as a cation in the future.