Uncovering the Role of Electronic Doping in Lead‐free Perovskite (CH3NH3)2CuCl4‐xBrx and Solar Cells Fabrication

An uncertain ratio: This study concerns the synthesis and properties of (CH₃NH₃)₂CuCl_4-x Br _x as an environmentally benign alternative to lead-based perovskites. This copper mixed halide perovskite exhibits a narrow absorption with a bandgap of 2.54–2.63 eV related to the halide ratio disparity, demonstrating the impact of halides to optimize methylammonium copper perovskite stability and provide a pathway to eco-friendly perovskites for optoelectronic applications.

Abstract

Lead halide perovskites are attractive pigments to fabricate solar cells in the laboratory, owing to their high power conversion efficiency. However, given the presence of Pb, such materials also have a high level of toxicity and are carcinogenic for humans and aquatic life. Arguably, this hampers their acceptability for immediate commercialization. This study entails the synthesis, optoelectronic properties, and photovoltaic parameters of two-dimensional copper-based perovskites as an environmentally benign alternative to lead-based perovskites. The perovskites – (CH₃NH₃)₂CuCl_4-x Br _x with x=0.3 and 0.66 – are derivatives of the stable (CH₃NH₃)₂CuCl₄. The single crystals and powders diffractograms suggest compositions with variations in Cl/Br ratio and dissimilar bromine localization in the inorganic framework. The copper mixed halide perovskite exhibits a narrow absorption with a bandgap of 2.54–2.63 eV related to the halide ratio disparity (crystal color variation). These findings demonstrate the impact of halides to optimize the stability of methylammonium copper perovskites and provide an effective pathway to design eco-friendly perovskites for optoelectronic applications.

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