Optimizing Cu+ Perovskite Chlorides for 24% Efficiency

Lead-free perovskite solar cells are promising as sustainable photovoltaics, but most of the copper-based alternatives are inefficient and unstable. The copper(I) perovskite chlorides (CuMCl3, M = Fe, Cr, Zn) are optimized by tuning the thickness and doping of the TiO2 electron transport layer, CuMCl3 absorber, and Spiro-OMeTAD hole transport layer, respectively, using SCAPS-1D simulations. The notable performance of CuZnCl3 (Voc = 0.79 V, Jsc = 38.2 mA·cm−2, FF = 80.2%) is observed due to the comparatively small bandgap (~1.10 eV) and appropriate thickness of the absorber (700 nm), achieving a balance between the generation of photocurrent and bulk recombination. The optimized n-i-p configuration yields power conversion efficiencies of 9.7% (CuFeCl3), 21.4% (CuCrCl3), and a relatively high 24.2% (CuZnCl3). CuCrCl3 works effectively (Voc = 0.99 V, Jsc = 25.1 mA·cm−2, FF = 86.15%) because it has a high dielectric constant and enables long diffusion. CuZnCl3 has a relatively good initial efficiency but considerable thermal sensitivity at 300–345 K, whereas CuFeCl3 has negligible thermal sensitivity. A rise in trap density leads to cation-dependent performance loss in all devices. This study proposes CuMCl3 as a promising lead-free perovskite platform for future photovoltaics.