Efficiency Advances in Thin CdSeTe/CdTe Solar Cells with CdMgTe at the Back

100 nm-thick CdMgTe with a 1.8-eV band gap was sputter-deposited at the back of 1.5-µm CdSeTe/CdTe bilayer absorbers to create a rear conduction-band offset and minimize the voltage deficit in the devices. With no additional applied heat during sputter deposition of the CdMgTe, the devices retained the necessary chlorine passivation of the absorber, a prevalent obstacle for CdTe-based devices with CdMgTe deposited by close-space sublimation. This in concert with minimal magnesium diffusion into the absorber and optimized copper doping has led to 16% efficiency in thin-absorber cells with a sputtered CdMgTe back layer.