Optical conductivity of highly mismatched GaP alloys

Highly mismatched alloys are promising for applications to intermediate-band (IB) solar cells. Here, we report first-principles prediction of intermediate bands in GaP on the basis of hybrid-density- functional theory, which enables to handle large supercells including defects with much better accuracy than semilocal functionals. Calculated optical conductivity reveals that the intermediate states due to co-doped Mg and O have sufficiently high optical transition probability. The multiple gaps are robust against thermalization. Intermediate-band states become more delocalized by hybridization with phosphorus-vacancy states, increasing the optical transition probability. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4773526]