Designing hole conductor free tin–lead halide based all-perovskite heterojunction solar cell by numerical simulation

Abstract

The simple structure and processing, low fabrication cost and high stability of the hole transport material (HTM)-free perovskite solar cells (PSCs) have great importance nowadays. In this study, an efficient and novel HTM-free PSC structure where CH3NH3Pb(I1-xClx)3/FA0.75Cs0.25Pb0.5Sn0.5I3 (where FA is formamidinium) acts as a light harvester, WS2 acts as an electron transport material (ETM) and carbon acts as the back electrode is proposed and was investigated numerically with the SCAPS-1D simulation tool. Initially three device structures having bare CH3NH3Pb(I1-xClx)3, CH3NH3Pb(I1-xClx)3/CsSnI3 and CH3NH3Pb(I1-xClx)3/FA0.75Cs0.25Pb0.5Sn0.5I3 absorbing layers with ZnO as an ETM were studied, and it was observed that among them the power conversion efficiency (PCE) of the CH3NH3Pb(I1-xClx)3/FA0.75Cs0.25Pb0.5Sn0.5I3-based device was the greatest. Also various ETMs and solar cell layer parameters, such as absorber thickness, defect density and doping concentration, were varied to obtain their optimum values. The optimum performance of the device thus achieved is VOC = 0.82 V, JSC = 31.94 mA/cm2, a fill factor of 77.95% and PCE of 20.53% with carbon as the back contact and VOC = 0.84 V, JSC = 34.34 mA/cm2, a fill factor of 78.54% and PCE of 22.72% with gold as the back contact. These simulation results indicate that the proposed new HTM-free PSC is quite efficient for photovoltaic applications.