Numerical Optimization of Cu2O as HTM in Lead-Free Perovskite Solar Cells: A Study to Improve Device Efficiency

Cu2O is a promising hole transport material (HTM) that offers the possibility to improve the power conversion efficiency (PCE) of the perovskite solar cells (PSCs). An escalation in the PCE of the non-toxic perovskite structures depends on the optimization of the HTM. This work aims to improve the PCE of the Cu2O/CH3NH3SnI3/PCBM/FTO and Cu2O/CH3NH3GeI3/PCBM/FTO solar cells by numerical simulation using SCAPS-1D. The variation of band-gap (2.0-2.6 eV), electron affinity (3.0-3.6 eV), acceptor density (10(17)-10(22) cm(-3)) and defect density (10(17)-10(22) cm(-3)) of Cu2O as HTM has been studied and optimized for obtaining maximum PCE of the solar cells. The energy band diagrams of the solar cell structures are compared at the optimized band-gap of Cu2O. The optimum absorber perovskite layer thickness is also investigated. Pt is proposed as the most suitable back contact metal for both solar cells. The photovoltaic parameters of the Cu2O/CH3NH3SnI3/PCBM/FTO solar cell are V-OC = 0.96 V, J(SC) = 33.91 mA/cm(2), FF = 81.36% and PCE = 27.08%. The photovoltaic parameters of the Cu2O/CH3NH3GeI3/PCBM/FTO solar cell are V-OC = 1.89 V, J(SC) = 15.86 mA/cm(2), FF = 88.82% and PCE = 26.68%. Both the solar cells showcased remarkable enhancement of PCE, which is higher than previous reports. The simulation results provide a viable route in the future to design highly efficient and stable Pb-free perovskite solar cells with modified electrical parameters of Cu2O.