19.5% Efficient CdSeTe/CdTe Solar Cells Using ZnO Buffer Layers

Incorporating transparent n-type buffer layers in the CdTe photovoltaic device structure has led to significant efficiency improvements. In this study, we report on the use of ZnO buffer layers to achieve high device efficiencies. The 50 nm and 100 nm thick buffer layers were deposited on 3.8 mm thick NSG TECT 15 glass substrates and then fabricated into arsenic doped CdSeTe/CdTe devices using First Solar's absorber. The device incorporating the 50 nm ZnO buffer layer achieved an efficiency of 19.5% without the addition of an anti-reflective coating. Results show that the highly efficient ZnO based devices are stable and do not develop the anomalous J-V behavior frequently observed with MgZnO buffer layers. While intrinsic ZnO buffers can be used to fabricate high efficiency devices, the performance is limited by interface recombination.