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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. [ABSTRACT FROM AUTHOR]

Bandgap engineering of Cu 2 In x Zn 1−x Sn(S,Se) 4 alloy films for photovoltaic application has been investigated. Cu 2 In x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.6) alloy films with different In contents and a single kieserite phase were fabricated by using a simple low-cost sol-gel method. The influence of In content on the structure, morphology, and optical and electrical properties of Cu 2 In x Zn 1−x Sn(S,Se) 4 films was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), X-Ray photoelectron spectroscopy (XPS), optical absorbance, and room-temperature Hall measurements. The results of XRD, TEM, and XPS demonstrated the substitution of some Zn atoms by In in Cu 2 In x Zn 1−x Sn(S,Se) 4 films. The Hall measurements show that the carrier concentration of the Cu 2 In x Zn 1−x Sn(S,Se) 4 (0 ≤ x ≤ 0.6) decreases with increasing In content and that the p-type Cu 2 In x Zn 1−x Sn(S,Se) 4 films with preferable electrical properties can be obtained by adjusting the In content during film deposition. The optical measurements indicate that the bandgap of Cu 2 In x Zn 1−x Sn(S,Se) 4 films with kesterite structure can be continuously tuned in the range of 1.13–1.01 eV as x is increased from 0 to 0.6. Our results show that the Cu 2 In x Zn 1−x Sn(S,Se) 4 alloy is a potentially applicable material for bandgap grading absorption layers in high-power-conversion-efficiency solar cells. [ABSTRACT FROM AUTHOR]