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

Abstract

Current perovskite solar cells reach high efficiencies with inexpensive materials and preparation methods. However, in order to understand the current values and obtain even higher efficiencies, the fundamental loss mechanisms of perovskite solar cells must be elucidated and predicted by appropriate models. Here, we adapt an analytical, drift-diffusion model for p-i-n solar cells and obtain accurate fits to measured current–voltage characteristics of planar hysteresis-free perovskite solar cells, covering a range of illumination intensities and perovskite thicknesses. Our results give values of carrier recombination lifetimes above 1 μ s, low effective recombination velocities at the interfaces between the perovskite layer and the surrounding layers around 1000 cm/s, built-in voltages that are slightly below the open-circuit voltages of around 1.05 V, and carrier mobilities around $\text{0.1} \text{cm}^{2}{\text{/Vs}}$ . The obtained parameters indicate that interface and bulk recombination are competing mechanisms, none of which can be ruled out in the case of the studied cells. Furthermore, we find that increasing the built-in voltage can significantly improve efficiency in p-i-n cells, while the implied relatively long diffusion length encourages the investigation of pn-type structures as ideal perovskite solar cell junctions.