Indium effect on structural, optical and electrical properties of Cu2InxZn1-xSnS4 alloy thin films for solar cell

The Cu2InxZn1-xSnS4 (0 <= x <= 0.8) alloy thin films were synthesized on soda lime glass (SLG) substrate by a simple low-cost sol-gel method. The influence of In content on the structural, morphology, optical and electrical properties of Cu2InxZn1-xSnS4 thin films was investigated by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), the scanning electron microscopy (SEM), optical absorbance and room temperature Hall measurements. The results indicated that the crystal structure changed from tetragonal to the mixture of tetragonal and cubic, as x varied from 0 to 0.8. The tetragonal type structure of Cu2InxZn1-xSnS4 could be stabilized at x = 0.5 without cubic CuInSnS4 phase separation. Morphological analysis showed the grain size and crystallinity have been enhanced as the x value increased from 0 to 0.4. The Cu2InxZn1-xSnS4 alloy thin film at x = 0.4 showed the best p-type conduction characteristics with a hole concentration of 1.06 x 10(15) cm(-3) and a hall mobility of 6.65 cm(2) V-1 s(-1). As the x increased to 0.5, the conductivity of films changed dramatically from p-to n-type. In addition, the optical band gap of Cu2InxZn1-xSnS4 alloy thin films with tetragonal kesterite could be continuously changed in range of 1.45-1.29 eV as the x value varied from 0 to 0.5. The Cu2InxZn1-xSnS4 alloy thin films should be ideal light-absorber material for achieving higher efficiency kesterite solar cells. (C) 2017 Elsevier Ltd. All rights reserved.