Interface-Dependent Current and Voltage Losses in a Lead-Free ZnSe/FASnI3/Cu2O Perovskite Solar Cell: A SCAPS-1D Study

This work examines a Glass/ITO/ZnSe/FASnI3/Cu2O/Au lead-free perovskite solar cell in SCAPS-1D, degrading the two absorber interfaces independently rather than together. The Cu2O/FASnI3 interface is shown to be the costlier one to degrade, taking 1.981 mA/cm2 of photocurrent and 5.02 percentage points of efficiency against 0.483 mA/cm2 and 3.41 percentage points at FASnI3/ZnSe, a photocurrent ratio of 4.10 at the highest defect density modeled. This ordering is the reverse of the ETL-side dominance reported for other lead-free absorbers, and the 0.80 eV electron barrier at Cu2O offers a plausible explanation, since electrons generated near that face must traverse the remaining absorber thickness before extraction at ZnSe. The device is also run under separate front and rear one-sun illumination, which leaves the photovoltage and fill factor nearly unchanged and concentrates the loss in photocurrent; because the modeled rear electrode is opaque Au, that result measures the electrical symmetry of the layer sequence rather than bifacial performance.