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

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 Pb²⁺ 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.