Fabrication of a self-powered broadband photodetector by 50% replacement of Pb by Mg in the CH3NH3Pb0.5Mg0.5Cl2I perovskite lattice

Abstract

Methyl ammonium lead halide (MAPbX₃) suffers from high toxicity of the Pb²⁺ cation leading to a major roadblock to its end-application. To alleviate the toxicity issue, a complete or partial substitution of Pb²⁺ by eco-friendly Mg-ions is attempted in the present study. The substitution of Pb²⁺ with Mg²⁺ cations in the MAPbX₃ crystal structure was carried out by tuning the stoichiometry of Mg²⁺ in MAPb_xMg_1−xCl₂I (for x = 0.1, 0.3, 0.5, 0.7, 0.9). Here MAPb_xMg_1−xCl₂I has been demonstrated for the first time in the application of a self-powered photodetector. A facile one-step anti-solvent approach has been used to synthesize the hybrid halide perovskite. Systematic structural and optical characterization indicates the formation of the desired tetragonal perovskite phase that exhibits a bandgap of 1.5–1.6 eV. The synthesized MAPb_xMg_1−xCl₂I has been used for device fabrication with (i) a simple hole transport material (HTM)-free configuration, and (ii) an economical carbon as the top electrode contact. MAPb_0.5Mg_0.5Cl₂I perovskite was found to be the best performing device, with an excellent responsivity of 153.74 mA W⁻¹ at zero bias, high detectivity of 6.5 × 10¹⁰ Jones, and a fast response/recovery time of 411 ms/50 ms. The optimum Mg substituted perovskite film thus yields an eco-friendly option compared to the conventional MAPbX₃ with nearly 50% replacement of the toxic Pb by benign Mg²⁺ cations. The demonstration of a MAPb_0.5Mg_0.5X₃-based novel performance photodetector thus paves an important path to the replacement of toxic Pb²⁺ in perovskite opto-electronic devices, thereby leading to eco-friendly devices.