Multifunctional interface passivation by benzothiophene amine for stable perovskite solar cells with suppressed charge recombination

Interfacial passivation is the focal point for the preparation of efficient and stable perovskite solar cells. A holistic modification strategy employing multifunctional interfacial material of [1]benzothieno[3,2-b][1]benzothiophene-2-amine (BTBT-NH2) between tin oxide and perovskite is presented in this paper. It can be chemically linked to tin oxide by Lewis base coordination to reduce the oxygen vacancy in tin oxide. Furthermore, BTBT-NH2 containing lone pair electrons can passivate unliganded lead ions in perovskite and anchor lead iodide completely at the bottom of perovskite through N-H bond, forming more nucleation sites and improving the film-forming quality and crystallinity of PbI2 and perovskite. Further analysis reveals that the modification of BTBT-NH2 can reduce trap density, thus suppressing charge recombination and improving power conversion efficiency (PCE). Surprisingly, after being stored at 22 °C and 30% relative humidity in ambient conditions for nearly 1000 h, the unpackaged device maintains 90% of its initial PCE. The results show that BTBT-NH2 interfacial modification is an effective strategy for obtaining stable and efficient perovskite solar cells.