Material Parameters and Perspectives for Efficiency Improvements in Perovskite Solar Cells Obtained by Analytical Modeling

Abstract

Current perovskite solar cells reach high efficiencieswith inexpensive materials and preparation methods. However, inorder to understand the current values and obtain even higher efficiencies,the fundamental loss mechanisms of perovskite solar cellsmust be elucidated and predicted by appropriate models. Here,we adapt an analytical, drift-diffusion model for p-i-n solar cellsand obtain accurate fits to measured current?voltage characteristicsof planar hysteresis-free perovskite solar cells, covering arange of illumination intensities and perovskite thicknesses. Ourresults give values of carrier recombination lifetimes above 1 μs,low effective recombination velocities at the interfaces between theperovskite layer and the surrounding layers around 1000 cm/s,built-in voltages that are slightly below the open-circuit voltagesof around 1.05 V, and carrier mobilities around 0.1 cm2/Vs. Theobtained parameters indicate that interface and bulk recombinationare competing mechanisms, none of which can be ruled outin the case of the studied cells. Furthermore, we find that increasingthe built-in voltage can significantly improve efficiency in p-i-ncells, while the implied relatively long diffusion length encouragesthe investigation of pn-type structures as ideal perovskite solar celljunctions.