Interfacial Defect Passivation and Charge Carrier Management for Efficient Perovskite Solar Cells via a Highly Crystalline Small Molecule

Minimizing the interfacial defects and improving the charge transferability of charge-transfer layers have become the most important strategies to boost the efficiency and stability of perovskite solar cells. However, most molecular passivators currently employed to alleviate interfacial defects generate poorly conductive aggregates at the interfaces, hindering the extraction of charge carriers. Here, a holistic interface engineering strategy employing a highly crystalline small molecule of 2,7-dioctyl[1]­benzothieno­[3,2-b]­[1]­benzothiophene (C8-BTBT) is reported. We reveal that C8-BTBT bridges the perovskite film to the hole-transporting layer with reduced interfacial defects and improved charge carrier management. Moreover, such interfacial modification with air-stable C8-BTBT achieves a desirable and robust morphology of Spiro-OMeTAD by reducing the aggregates. Accordingly, C8-BTBT-treated devices exhibit a great enhancement to all photovoltaic performance characteristics with an absolute efficiency improvement exceeding 2%. The C8-BTBT-modified Spiro-OMeTAD enables decent thermal tolerance, which paves the way for enhancing the performance of Spiro-OMeTAD-based perovskite optoelectronics.