Efficient Inverted Perovskite Solar Cells with Low Voltage Loss Achieved by a Pyridine-Based Dopant-Free Polymer Semiconductor

Currently, the performance improvement for inverted perovskite solar cells (PVSCs) is mainly limited by the high open circuit voltage (V-OC) loss caused by detrimental non-radiative recombination (NRR) processes. Herein, we report a simple and efficient way to simultaneously reduce the NRR processes inside perovskites and at the interface by rationally designing a new pyridine-based polymer hole-transporting material (HTM), PPY2, which exhibits suitable energy levels with perovskites, high hole mobility, effective passivation of the uncoordinated Pb2+ and iodide defects, as well as the capability of promoting the formation of high-quality polycrystalline perovskite films. In absence of any dopants, the inverted PVSCs using PPY2 as the HTM deliver an encouraging PCE up to 22.41 % with a small V-OC loss (0.40 V), among the best device performances for inverted PVSCs reported so far. Furthermore, PPY2-based unencapsulated devices show an excellent long-term photostability, and over 97 % of its initial PCE can be maintained after one sun constant illumination for 500 h.

Automated summary

This study presents a new pyridine-based polymer hole-transporting material, PPY2, that can simultaneously reduce non-radiative recombination processes in inverted perovskite solar cells. By using PPY2, the research has successfully improved the performance metrics of PVSCs and achieved good long-term photostability.