Numerical optimization of photovoltaic performance of cesium titanium bromide perovskite solar cells using dual copper oxide hole transport layers

This work provides a comprehensive numerical evaluation by using SCAPS-1D software for designing efficient lead-free Cs2TiBr6-based perovskite solar cells (PSCs) based on all-inorganic carrier transport layers. The copper oxide hole transport layer (HTL) is introduced in the Cs2TiBr6-based PSC for the first time, recording a power conversion efficiency (PCE) that is superior to the values reported in the literature. The prototype FTO/CeOx/Cs2TiBr6/Cu2O/CuO/Au cell achieved a power conversion efficiency (PCE) of 8.67%. Optimization of several factors, including layer thickness, defect density, interface defect density, back metal contact, electron capture cross-section, and absorber bandgap, yielded an enhanced PCE of 30.75% for the optimized FTO/CeOx/Cs2TiBr6/Cu2O/CuO/Pt PSC. Simplified device architectures were investigated. The simple FTO/CeOx/Cs2TiBr6/Cu2O/Pt cell delivered a comparable PCE of 30.76%. The HTL-free FTO/CeOx/Cs2TiBr6/Pt design recorded a lower PCE of 22.32%. The optimized Cu2O/CuO HTL-assisted device exhibited robust thermal performance, with only a modest decrease in PCE (30.99% to 28.16%) with increasing temperature (290 K--400 K). The improved photovoltaic performance of the optimized HTL-assisted devices can be attributed to enhancement in light absorption and carrier generation. An increased built-in field and improved carrier collection also contributed to this improvement. The higher work function of Pt (5.7 eV) formed a better ohmic back contact with the optimized devices, further improving carrier collection.