Improving Lead-Free MAGeI3 Perovskite Solar Cell Performance with Ce-ZnO:Al Electron Transport Layer: a Numerical Study

The main challenge for commercialization of perovskite solar cells is to substitute lead without compromising the performance. We investigate the potential of methylammonium germanium iodide (MAGeI3) as a light-absorbing layer in a device structure of cerium-doped zinc oxide (Ce-ZnO:Al) as an electron-collecting layer and spiro-OMeTAD as a hole-collecting layer with the configuration ITO/ Ce-ZnO:Al/MAGeI3/Spiro-OMeTAD/Au, extensively simulated by SCAPS-1D. We selected both transport layers based on the matching of the energy levels with the absorber and their ability to extract charge from the absorber. A parametric study of the absorber thickness, doping and defect concentrations identified the parameters that most strongly control performance, and a further study of the ETL thickness, doping and interface defect states identified the main design trade-offs. The device shows a VOC of 1.1054 V, a fill factor of 81.44%, a JSC of 34.52 mA/cm2, and a PCE of 28.45% at the optimal condition, and the quantum efficiency is stable in the temperature range of 275–450 K. Collectively, these results point to the possibility of employing well-matched and optimized transport layers in MAGeI3 for lead-free photovoltaics.