Numerical simulation to optimize the efficiency of HTM-free perovskite solar cells by ETM engineering

Perovskite solar cells based on carbon electrodes (c-PSCs) without a hole transport material (HTM) have gained considerable interest owing to their cost-effective and simplified structure. However, their application is con-strained by a combination of low efficiency and the prevalence of electron transport materials (ETMs), e.g., TiO2, which undergo extreme temperatures during their manufacturing processes. TiO2 also has poor optoelectronic properties, such as low conductivity and mobility. Additionally, when exposed to UV light, TiO2 susceptibility to photocatalysis reduces the materials long-term stability. In present study, an HTM-free device based on FTO/ TiO2/CH3NH3PbI3/carbon structure is employed and studied using a one-dimensional Solar Cell Capacitance Simulator (SCAPS-1D). Initially, the design is studied while employing inorganic ETMs, including CdZnS, WS2, WO3, ZnO, ZnOS, and ZnSe, by substituting TiO2, and the impact of each ETM on device performance is eval-uated. After ETM optimization, various parameters that affect device performance, such as ETM and absorber thicknesses, doping concentrations, charge carriers mobility, and defect densities at ETM/perovskite interface, have been studied. Under optimized parameters, the design having ZnSe as ETM yields the best results with a Voc of 1.25 V, Jsc of 24.77 mA/cm2, FF of 86.29 %, and PCE of 26.76 %. The presented results thus add more promise and confidence to the for HTM-free PSCs.