Photoconversion Efficiency Modeling in Perovskite Solar Cells

A theoretical approach to model photoconversion efficiency in perovskite p-i-n structures is developed and used to analyze the experimental results published in the literature. It is shown that the surface of a formamidinium lead iodide (FAPbI
₃
) solar cell (SC) is spontaneously textured, whereas the surface of a CH
₃
NH
₃
PbI
₃
SC is not. The current-voltage curve ideality factor equals 2 for FAPbI
₃
and 2.3 for CH
₃
NH
₃
PbI
₃
-based SCs. This value is due not to recombination in the space-charge region. Rather, it can be explained by taking into account the contribution of the rear surface at high injection level. In the limit of negligible Shockley-Read-Hall and surface recombination and in the absence of optical losses, photoconversion efficiency for both materials is 29.2% at i-layer thickness of ca. 1 μm. When these recombination losses are taken into account, the maximal efficiency reduces to about 20%.