High Performance Inverted Perovskite Solar Cells via Heteroatom-Containing Multifunctional Spiro Self-Assembled Monolayers.

In inverted perovskite solar cells (PSCs), the arrangement of self-assembled hole-transporting monolayers (SAMs) on substrates and their interaction with perovskite layer are critical for device efficiency and stability. Herein, two spiro SAMs are developed by introducing O and S atoms into the structure, named Spiro-O and Spiro-S, respectively. On one hand, the unique orthogonal molecular configuration of the spiro structure weakens intermolecular π-π interactions, thereby inhibiting molecular aggregation. This ensures uniform coverage on the substrate and a homogeneous surface potential distribution. On the other hand, the lone pair electrons of the introduced heteroatoms can interact with the Pb ions, enhancing the quality of the perovskite film and effectively passivating the defects at the perovskite/SAM interface. The experimental and theoretical results show that the S in Spiro-S strongly interacts with perovskite, resulting in the formation of a more uniform and higher-quality crystalline perovskite layer. Compared to PSCs based on Spiro-O, the device with Spiro-S shows decreased defects at the buried interface, ultimately achieving an impressive power conversion efficiency of 25.75% (certified 25.19%). Furthermore, the PSCs based on Spiro-S also exhibit better long stability; the unencapsulated champion devices retain 92% of the initial efficiency after being stored at 25 °C for 1200 h.