Aryl quaternary ammonium modulation for perovskite solar cells with improved efficiency and stability

The device lifetime is increasingly one of the most challenging issues in –perovskite solar cells (PSCs). Introducing an interlayer has been proven to be a promising strategy to enhance device stability. While the commonly used interlayers are based on several developed materials, such as alkyl quaternary ammonium, including TBAI, CTBA, etc. And the corresponding mechanism lacks system research. Herein, we introduced a novel modulator, aryl quaternary ammonium (TMPMAI), featuring the phenyl group connected with the commonly used alkyl quaternary ammonium to improve device durability and efficiency. It was found the non-radiative recombination can be significantly suppressed by TMPMAI and the corresponding mechanisms are attributed to not only the defect passivation, but also a type-I gradient energy alignment. DFT calculations demonstrated the introduced phenyl group takes a crucial role. More importantly, TMPMAI modulation stabilizes perovskite/HTL interface by preventing severe degradation at interface like delamination. Benefiting from the optimized perovskite/HTL interface, an efficiency of 23.1% and a fill factor of nearly 83% are achieved, together with excellent stability.