Can fullerene derivative PCBM serve as an innovative hole transport material for CsPbBr3 perovskite solar cells?

The PCBM modification layer can effectively adjust the interface energy level, significantly facilitating hole transport at the PVK/electrode interface. Furthermore, the modification of PCBM efficiently passivates uncoordinated Pb2+ ions, promoting the formation of high-quality PVK films. Additionally, the introduction of PCBM significantly improves the hydrophobicity of the device, thereby enhancing its long-term stability. [Display omitted] •This study represents the first instance of utilizing the hole transport capabilities of (6,6)-Phenyl C61-butyric acid methyl ester (PCBM) in this article.•The modification of PCBM effectively facilitates hole transport at the PVK/electrode interface, substantially inhibiting non-radiative recombination.•Furthermore, the carbonyl groups present in PCBM efficiently passivate uncoordinated Pb2+, thereby reducing the defect density within the PVK films.•The PCBM-modified device demonstrates excellent long-term stability, attributed to the notable hydrophobicity of PCBM. The absence of hole transport layers (HTL) in typical CsPbBr3 perovskite solar cells (PSCs) leads to an energy level mismatch at the perovskite layer (PVK)/electrode interface, causing significant non-radiative recombination and charge loss at this interface. This issue hinders the efficiency enhancement of CsPbBr3 PSCs. In this study, we utilize the hole transport capabilities of (6,6)-Phenyl C61-butyric acid methyl ester (PCBM) for the first time, applying it to the surface of PVK films. Our results demonstrate that PCBM modification effectively adjusts the interface energy level, significantly facilitating hole transport at the PVK/electrode interface while inhibiting electron backflow. This modification markedly reduces non-radiative recombination at the interface. Additionally, the carbonyl groups provided by PCBM efficiently passivate uncoordinated Pb2+, thereby decreasing the defect density within the PVK films. Consequently, while the illuminated area of devices is 0.0625 cm2, the device with PCBM achieves a champion power conversion efficiency (PCE) of 10.11 % with an outstanding open-circuit voltage (VOC) of 1.63 V, benefiting from favorable charge transport and high-quality PVK films. Furthermore, the unencapsulated device demonstrates excellent long-term stability, retaining 98.4 % of its initial PCE, attributed to the notable hydrophobicity of PCBM. Our work highlights the potential of PCBM to optimize the performance and stability of CsPbBr