Few-Layered Black Phosphorene as Hole Transport Layer for Novel All-Inorganic Perovskite Solar Cells

The CsPbBr₃ perovskite exhibits strong environmental stability under light, humidity, temperature, and oxygen conditions. However, in all-inorganic perovskite solar cells (PSCs), interface defects between the carbon electrode and CsPbBr₃ limit the carrier separation and transfer rates. We used black phosphorus (BP) nanosheets as the hole transport layer (HTL) to construct an all-inorganic carbon-based CsPbBr₃ perovskite (FTO/c-TiO₂/m-TiO₂/CsPbBr₃/BP/C) solar cell. BP can enhance hole extraction capabilities and reduce carrier recombination by adjusting the interface contact between the perovskite and the carbon layer. Due to the coordination of the energy structure related to interface charge extraction and transfer, BP, as a new type of hole transport layer for all-inorganic CsPbBr₃ solar cells, achieves a power conversion efficiency (PCE) that is 1.43% higher than that of all-inorganic carbon-based CsPbBr₃ perovskite solar cells without a hole transport layer, reaching 2.7% (Voc = 1.29 V, Jsc = 4.60 mA/cm², FF = 48.58%). In contrast, the PCE of the all-inorganic carbon-based CsPbBr₃ perovskite solar cells without a hole transport layer was only 1.27% (Voc = 1.22 V, Jsc = 2.65 mA/cm², FF = 39.51%). The unencapsulated BP-based PSCs device maintained 69% of its initial efficiency after being placed in the air for 500 h. In contrast, the efficiency of the PSC without HTL significantly decreased to only 52% of its initial efficiency. This indicates that BP can effectively enhance the PCE and stability of PSCs, demonstrating its great potential as a hole transport material in all-inorganic perovskite solar cells. BP as the HTL for CsPbBr₃ PSCs can passivate the perovskite interface, enhance the hole extraction capability, and improve the optoelectronic performance of the device. The subsequent doping and compounding of the BP hole transport layer can further enhance its photovoltaic conversion efficiency in PSCs.