Monocrystalline 1.7-eV-Bandgap MgCdTe Solar Cell With 11.2% Efficiency

This work demonstrates a monocrystalline 1.7 eV Mg0.13Cd0.87Te solar cell with an open-circuit voltage of 1.176 V and an active-area efficiency of 11.2%. The absorber layer is clad in wider bandgap passivation layers that effectively confine electrons and holes via the resulting band offsets. The potential barriers cladding the absorber are generated using higher magnesium compositions than the absorber and provide excellent carrier confinement. This ultimately leads to long minority carrier lifetimes (>500 ns) and high photoluminescence quantum efficiencies yielding an implied open-circuit voltage of 1.3 V. However, the same barriers at the heterointerfaces reduce fill factor by impeding transport; this is apparent as series resistance losses that can be overcome with operation at higher temperatures. The photocurrent loss mechanisms are simulated and analyzed, laying out the pathway for further improvements in current generation and, thus, efficiency.