Transition metal nitride contacts for CdTe photovoltaics

CdS/CdTe thin film photovoltaics were produced with transition metal nitrides (TMNs) as back contacts. The devices show photovoltaic activity but a significant Schottky barrier was found at the back contact. Solar cells perform better as the ZrN films are thicker due to improved microstructure. The good reflectance of ZrN makes it acts as a reflective layer to reduce optical losses and lower the thickness of CdTe. Pure N₂ plasma treatment of the back surface of the CdTe and annealing did not improve the performance. A thin layer of Cu was introduced to dope the CdTe and completed with a ZrN film but more amount of Cu deteriorates the performance. Although the nitrides are highly stable and have good electrical properties, we have not been able to obtain devices to date that are not limited by the back contacts.