2D Perovskite Capping Layer Enabling Stable Perovskite Photovoltaics

Interfacial passivation plays a pivotal role in achieving efficient and stable perovskite solar cells. Meanwhile, the introduction of 2D perovskites has also been widely reported to be beneficial for enhancing the performance and stability of devices. Herein, DEAI is used as an ammonium salt, which is spin coated onto the surface of the perovskite film, resulting in the formation of a 2D perovskite phase. This alteration increases the film's hydrophobicity, holding the promise of enhancing its humidity stability. Furthermore, DEAI effectively reduces trap density in the perovskite layer, suppressing nonradiative recombination and optimizing the surface potential, thereby improving the efficiency of devices. As a result, the inverted perovskite devices passivated with DEAI achieve a champion power conversion efficiency of 24.26%. Additionally, the unencapsulated DEAI‐passivated perovskite solar cells demonstrate enhanced stability.