Performance enhancement of 3D and 2D all-inorganic CuxAgBiI4+x solar cells under the influence of LED illumination

The pursuit of sustainable, lead-free alternatives to conventional lead-halide perovskite materials has led to the exploration of copper-silver-bismuth halides. These materials have emerged as favorable candidates for optoelectronic applications owing to their stability, tunable band gaps, and light absorption capabilities. This simulation study examines the performance enhancement of all-inorganic wide bandgap Cu_xAgBiI_4+x solar cells under indoor lighting conditions, specifically using white LED illumination at 1000 lux and different color temperatures (7500 K and 2900 K). The baseline cell, featuring FTO/c-TiO₂/m-TiO₂/Cu_xAgBiI_4+x/Spiro-OMeTAD, is firstly calibrated with the device model to validate SCAPS device simulator outcomes. Both the 3D CuAgBiI₅ and 2D Cu₂AgBiI₆ structures are then optimized for indoor photovoltaics (IPVs). The first phase of optimization addresses the conduction band offset (CBO) between the electron transport layer (ETL) and absorber layer materials in order to reduce interfacial recombination and improve carrier transfer efficiency. The second phase focuses on optimizing the absorber characteristics, including thickness and defect density, maximizing photon absorption and minimizing recombination losses. The results demonstrate significant improvements in power conversion efficiency (PCE), with Cu₂AgBiI₆ showing superior performance compared to CuAgBiI₅, particularly under cool LED (7500 K) illumination (1000 lux). Specifically, the PCE of CuAgBiI₅ increased from 1.01 % to 6.57 % and then to 17.70 % following the first and second optimization phases, respectively. In comparison, the PCE of Cu₂AgBiI₆ enhanced from 5.14 % to 9.67 % and 21.21 % after the first and second optimization phases, respectively.