Impact of tellurium anion distribution depending on doping concentration and substrate temperature on the photovoltaic performance of Cu(In,Ga)Se2 thin film solar cells

Abstract

We explored how tellurium (Te) anion distribution as a function of doping concentration and substrate temperature effects on the photovoltaic (PV) performance of narrow-bandgap Cu(In, Ga)Se2 thin film solar cells grown by a three-stage co-evaporation process. At low and moderate substrate temperatures (480 ℃ and 550 ℃), the inclusion of Te anions in the structure has negative impacts on photovoltaic parameters due to formation of disorder in the crystal structure, the deepening of the notch in the GGI gradient and the increase of defect-assisted recombination. At high substrate temperature (620 ℃), conversely, the presence of Te not only serves to improve the crystal structure and mitigate recombination through defect suppression but also facilitates the growth of large grains and attains a near-optimal GGI ratio (0.3) with a better gradient, which has a beneficial impact on the PV performance. These results highlight the role of Te anion distribution on PV performance of Cu(In, Ga)Se2 thin film solar cells and its potential for highly efficient commercial thin-film solar cells in reasonable and effective ways as a function of substrate temperature and doping concentration.