Effect of PCBM nanoparticles in lead-based layered (PEA)2PbI4 perovskite thin films†

Two-dimensional (2D) layered halide perovskites are considered to be one of the future potential semiconductor materials due to their higher moisture stability than three-dimensional (3D) perovskites. However, improving their optical and electrical properties is still necessary for critical applications. The technique of additive engineering can be utilized to tune and enhance the optoelectrical properties of the 2D perovskites. This work studies the impact of mixing a certain amount of a fullerene derivative ‘[6,6]-phenyl C₆₁-butyric acid methyl ester’ (PCBM) into 2D (PEA)₂PbI₄ perovskite thin films (PEA = phenyl ethyl ammonium). The studies show that PCBM does not affect the structure and bandgap of the (PEA)₂PbI₄ perovskite. On the other hand, PCBM improves photoluminescence emission intensity and promotes charge separation at the perovskite/PCBM interface. Further studies convey that, even though PCBM can heal certain defect states in the (PEA)₂PbI₄ perovskite material, the electrons generated under intense illumination at the perovskite/PCBM interface are trapped by this fullerene derivative. Hence, PCBM plays a dual role when mixed with the (PEA)₂PbI₄ perovskite, as (1) a defect healing agent and (2) an electron acceptor. However, over continuous illumination on the (PEA)₂PbI₄ perovskite thin films, the photoexcited electrons are trapped by PCBM. As a result, the photocurrent response and the photocatalytic reaction rate get reduced in PCBM mixed (PEA)₂PbI₄ perovskite thin films.