Synthesis and investigation of environmental protection and earth-abundant kesterite Cu2MgxZn1-xSn(S,Se)4 thin films for solar cells

Abstract We have synthesized Cu 2 Mg x Zn 1–x Sn(S,Se) 4 (0 ≤ x ≤ 0.6) thin films by a facile sol-gel method, and studied the influence of Mg concentration on the crystal structure, surface morphology and photoelectric performance of Cu 2 Mg x Zn 1–x Sn(S,Se) 4 thin films systematically. It was shown that the smaller Zn 2+ in Kesterite phase Cu 2 ZnSn(S,Se) 4 will be replaced by larger Mg 2+ , forming uniform pure phase Cu 2 Mg x Zn 1–x Sn(S,Se) 4 . The band gap of Cu 2 Mg x Zn 1–x Sn(S,Se) 4 films can be adjusted from 1.12 to 0.88 eV as the x value changes from 0 to 0.6. Furthermore, the Cu 2 Mg x Zn 1–x Sn(S,Se) 4 thin films with large grain size, smooth surface and less grain boundaries was obtained at an optimized condition of x = 0.2. The carrier concentration of Cu 2 Mg x Zn 1–x Sn(S,Se) 4 thin film reaches the maximum 6.47 × 10 18 cm −3 at x = 0.2, which is a potential material to be the absorption layer of high efficiency solar cells.