Improvement of Cu₂ZnSnS₄ solar cell characteristics with Zn(O_x,S_1-x) buffer layer

This experiment investigated characteristic changes in a Cu₂ZnSnS₄(CZTS) solar cell by applying a Zn (O_x,S_1-x) butter layer with various compositions on the upper side of the absorber layer. Among the four single layers such as Zn(O_0.76,S_0.24), Zn(O_0.56, S_0.44), Zn(O_0.33,S_0.67), and Zn(O_0.17,S_0.83), the Zn(O_0.76,S_0.24) buffer layer was applied to the device due to its bandgap structure for suppressing electron-hole recombination. In the application of the Zn(O_0.76,S_0.24) buffer layer to the device, the buffer layer in the device showed the composition of Zn(O_0.7,S_0.3) because S diffused into the buffer layer from the absorber layer. The Zn(O_0.7,S_0.3) buffer layer, having a lower energy level (E_V) than a CdS buffer layer, improved the JSC and VOC characteristics of the CZTS solar cell because the Zn(O_0.7,S_0.3) buffer layer effectively suppressed electron-hole recombination. A substitution of the CdS buffer layer by the Zn(O_0.7,S_0.3) buffer layer improved the efficiency of the CZTS solar cell from 2.75% to 4.86%.