Transparent Buffer Layer for Back Surface Passivation in CdTe Photovoltaics

The realization of a transparent back buffer layer would be a significant boon for the CdTe community. Simulations presented here reveal a substantial performance increase in ultrathin cells through incorporation of a back buffer, as well as high bifaciality if transparent contacts are assumed. This project aims to deposit a p-type transparent conducting oxide (TCO) at the back of superstrate CdSeTe/CdTe cells to improve band bending and interface recombination at the rear of the cell, and ultimately to bring high performing bifacial cells to fruition. Four such oxides were sputter deposited to create a collection of functional bifacial cells. Back surface passivation was evaluated with rear-excitation time-resolved photoluminescence (TRPL). Several promising materials yielded rear-excitation lifetimes >2 ns, indicating effective passivation.