First principles study of defect properties of II-VI photovoltaic materials

First-principles study of photovoltaic materials plays an important role in developing solar cell technologies because it can provide useful physical insights, fresh perspective and new design principles for developing innovative solar cell materials with high solar power conversion efficiency and reduced cost. Similar to other semiconductors, one of the most important issues in slolar cell absorber materials are to control the defects, either for introducing charge carrier, improving charge transport, or reducing non-radiative carrier recombination. For example, a good solar cell material should have good defect properties, that is, it can be easily doped such that charge carriers can be created to generate the required electric field and has less defect-induced recombination centers such that it has high carrier life time and minority carrier mobility, so photo-generated charge can be easily collected. In this talk, using II-V thin-film solar cell absorber materials Cd(Te,Se), Cu(In,Ga)Se₂ (CIGS) and Cu₂ZnSnS2 (CZTS) as examples, I will discuss how theoretical first-principles studies can be used to better understand and optimize the solar cell performance.