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

We have synthesized Cu2MgxZn1-xSn(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 Cu2MgxZn1-xSn(S,Se)4 thin films systematically. It was shown that the smaller Zn2+ in Kesterite phase Cu2ZnSn(S,Se)4 will be replaced by larger Mg2+, forming uniform pure phase Cu2MgxZn1-xSn(S,Se)4. The band gap of Cu2MgxZn1-xSn(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 Cu2MgxZn1-xSn(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 Cu2MgxZn1-xSn(S,Se)4 thin film reaches the maximum 6.47 × 1018 cm−3 at x = 0.2, which is a potential material to be the absorption layer of high efficiency solar cells.