A Universal Dopant-Free Polymeric Hole-Transporting Material for Efficient and Stable All-Inorganic and Organic-Inorganic Perovskite Solar Cells

Abstract

Hole-transporting materials (HTMs) with desired properties play a crucial role in achieving efficient and stable perovskite solar cells (PSCs). However, most high-performance devices generally employ HTMs that require additional complicated doping treatments, which are harmful to the device stability. In this work, a fluorine-substituted polymer electron-donor material, PM6, is developed as a dopant-free HTM in regular all-inorganic CsPbI₂Br PSCs. Benefiting from the matched energy-level alignment, high hole mobility, and effective defect passivation, a champion power conversion efficiency (PCE) of 16.06% with an ultrahigh fill factor of 82.54% is achieved for the PM6-based PSCs. Compared to doped Spiro-OMeTAD (PCE of 14.46%), PM6 significantly enhances the PCE of CsPbI₂Br PSCs with negligible hysteresis owing to its more efficient charge transportation, suppressed recombination, and strong trap passivation effect. Moreover, remarkable improvements in long-term stability, thermal stability, and operational stability are all gained for the PM6-based PSCs. In addition, the successful application of PM6 as a dopant-free HTM in organic-inorganic hybrid PSCs enables an impressive PCE of 20.05% with superb device stability, manifesting the generality of the polymer donor material in various PSC systems.

Keywords: CsPbI2Br; all-inorganic perovskite solar cells; device stability; dopant-free; hole-transport material.