Efficient and Stable Inverted Perovskite Solar Cells Enabled by a Fullerene-Based Hole Transport Molecule

Designing an efficient modification molecule to mitigate non-radiative recombination at the NiO_x/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high-performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene-based hole transport molecule, designated as FHTM, by integrating C₆₀ with 12 carbazole-based moieties, and applied it as a modification molecule at the NiO_x/perovskite interface. The in situ self-doping effect, triggered by electron transfer between carbazole-based moiety and C₆₀ within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high-quality perovskite films. These combined improvements led to the FHTM-based PSCs yielding a champion efficiency of 25.58 % (Certified: 25.04 %), notably surpassing that of the control device (20.91 %). Furthermore, the unencapsulated device maintained 93 % of its initial efficiency after 1000 hours of maximum power point tracking under continuous one-sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs.