Interface induced in-situ vertical phase separation from MAPbI3:Spiro-OMeTAD precursors for perovskite solar cells

The major obstacles delaying the commercialization of thin film solar cells based on hybrid organic halide perovskite are the expensive materials, instability of the devices and the complicated multi-step fabrication process. To solve these challenges, we present a simple and high material utilization strategy which employing the polyethyleneimine (PEI) interface abduction to in-situ fabricate perovskite layer and hole transporting layer (HTL) from MAPbI(3) and Spiro-OMeTAD (SPI) mixed precursors in single step. Analyzation find that the in-situ phase separation is induced by the PEI abduction. The existence of PEI blocks SPI form Ti-O bond with bottom TiO2 surface and converting the interaction between SPI and bottom interface to Van der Waals interaction. Employing this fabrication technique for PSCs, remarkably improves materials utilization of perovskite and SPI, as well as exhibiting superior stability of about 95% initial efficiency even after 68 days of storage in ambient condition without encapsulation. We believe that our strategy will pave a new way for simple, economical and stable PSCs preparation, and provide an inspiration to simplify fabrication process for organic-inorganic electronic devices.