Study on the intermediate band formation and photovoltaic properties of Ti-doped p-CuGaS2 compound via heat injection

In order to discuss the intermediate band (IB) formation mechanism, influence on photoelectric conversion, electron transition process and other photovoltaic properties of Ti-doped p-CuGaS 2 light absorption material, p-CuGaS 2 and Ti-doped p-CuGaS 2 were synthesized through low-cost heat injection and annealing. Structural characterization results indicate that Ti 3 + partially replaced Ga 3+ in the Ti-doped p-CuGaS 2 . Two additional sub-band absorption peaks of Ti-doped p-CuGaS 2 confirm the formation of an IB. The band structures are confirmed by optical analysis and ultraviolet photoelectron spectroscopy, and the electron transition processes—from the valence band (VB) to the conduction band (CB), the valence band (VB) to the IB, and the IB to the conduction band (CB)—are analyzed. The IB formation mechanism is discussed using the band structure and theoretical calculations derived from density functional theory. A thin-film solar-cell model with Ti-doped p-CuGaS 2 as the absorbing layer is created. Numerical simulations based on experimental data show that the photoelectric conversion efficiency increase from 15.06 % for CuGaS 2 to 25.46 % for Ti-doped p-CuGaS 2 because of the IB effect, which enhances the optical absorption and extends the spectral response range. In conclusion, the research findings will establish a fundamental basis for the exploration of intermediate-band solar cells based on copper gallium sulfide.