Solution processed PCBM-CH₃NH₃PbI₃ heterojunction photodetectors with enhanced performance and stability

In this work, an anti-solvent process was used to fabricate a perovskite-PCBM bulk heterojunction, in which PCBM diffused in CH₃NH₃PbI₃ and passivated grain boundary defects. Different concentrations of PCBM were studied in this paper. When a low concentration (5 mg/ml, 10 mg/ml or 15 mg/ml) of PCBM was used, the PCBM-CH₃NH₃PbI₃ transition layer provided efficient electron collection. With the increase of the concentration of PCBM, a thicker PCBM layer was formed in the bulk heterojunction. Such a thick PCBM resulted in rough perovskite morphology and low photo-carrier collection efficiency. SEM images and metallographic microscope images confirmed that the PCBM upper layer gradually covered grain boundaries of perovskite films with the increase of the PCBM concentration. On the other hand, low concentrations of PCBM improved the light absorption and crystallinity of CH₃NH₃PbI₃ films. The PCBM/perovskite heterojunction exhibited a high UV responsivity of 0.18 AW^-1 and a response time less than 123 ms. This research provides a way to improve the quality of perovskite films and the performance of perovskite photodetectors.