Improving CdSeTe Devices With a Back Buffer Layer of Cu x AlO y

The open-circuit voltage (Voc) of CdTe-based photovoltaics may be limited by carrier recombination at interfaces (front or back) or in the absorber layer. Reduction in recombination of a given dominant mechanisms can lead to improved device performance if the remaining mechanisms turnonin a narrow bias range just below the open circuit voltage. In this article, we demonstrate enhanced performance by incorporating solution-processed CuxAlOyto form a back-buffer layer in CdSe/CdTe devices. Outstanding minority carrier lifetimes of 656 and 4.2 ns were measured with glass side and film side illumination for device stacks processed with CuxAlOy. Devices demonstrated efficiencies of up to 17.4% withVocof 859 mV, FF of 75.6% andJscof 26.9 mAcm−2while the efficiency of the reference device without the back-buffer layer was 16.5% withVocof 839 mV, FF of 70.6%, andJscof 27.9 mAcm−2.