Influence of defect pairs in Ga-based ordered defect compounds: A hybrid density functional study

In the present paper, density functional theory (DFT) based calculations have been performed to predict the stability, electronic, and optical properties of Ga-rich ordered defect compounds (ODCs). The calculated lattice constants, bulk modulus, their pressure derivatives, and optical constants show good agreement with available experimental data. The hybrid exchange correlations functional have been considered to calculate ground state total energy and energy band gap of the material. The calculated formation energy of ODCs comes smaller than pure CuGaSe2 (CGS). Our calculated optical absorption coefficients indicate that the energy band gap of ODCs can be tuned by changing the number of donor-acceptor defect pairs (2V(cu)(-), + Ga-cu(2+)). The band offset has been calculated to understand the reason of band gap alteration while the number of defect pair changes. Our results may be helpful for other experiments to further improve the performance of ODCs.