Suppressing Nonradiative Recombination and Enhancing Hole Density in CdSe_<i>x</i>Te_1–<i>x</i> Solar Cells through As Doping and Se Alloying: A Hybrid Functional Study

Group-V doping and Se alloying have been proven promising strategies for improving the device performance of CdTe solar cells by achieving high hole density and open-circuit voltage. However, defect properties of group-V substitutes, XCh (X = P, As, or Sb; Ch = Se or Te), in CdSexTe1–x are not clear. By performing first-principles hybrid functional calculations, we systemically investigate the defect properties of XCh in CdSexTe1–x. It is revealed that XCh acceptors become deeper as the Se composition x increases, which is mainly due to the lowered valence bands of CdSexTe1–x. Moreover, the defect formation energies of XCh also increase with x. AsCh is revealed to have the lowest formation energy among the three XCh acceptors. Arsenic is proven to be the best group-V dopant in CdSexTe1–x despite its acceptor level being a little deeper than PCh. Our results predicted that a high hole density exceeding 1017 cm–3 can be achieved by As doping under Cd-rich and X-rich conditions at a growth temperature of 850 K. Se alloying can suppress the formation of nonradiative recombination centers, and As doping does not result in nonradiative recombination.