Electronic band alignment at CuGaS2 chalcopyrite interfaces

Cu-chalcopyrite semiconductors are commonly used as light absorbing materials on solar cell devices. The study of the heterointerfaces between the absorbent and the contact materials is crucial to understand their operation. In this study, band alignments of the heterojunctions between CuGaS2 chalcopyrite and different semiconductors have been theoretically obtained using density functional theory and more advanced techniques. Band alignments have been determined using the average electrostatic potential as reference level. We have found that the strain in the heterointerfaces plays an important role in the electronic properties of the semiconductors employed here. In this work CuAlSe2/CuGaS2 and CuGaS2/ZnSe heterointerfaces show band alignments where holes and electrons are selectively transferred through the respective heterojunctions to the external contacts. This condition is necessary for their application on photovoltaic devices.