ABSTRACT
Improving the performance of kesterite solar cells requires high-quality, defect-free CZTS(Se) films with a reduced number of secondary phases and impurities. Post-annealing of the CZTS films at high temperatures in a sulfur or selenium atmosphere is commonly used to improve the quality of the absorbing material. However, annealing at high-temperatures can promote material decomposition, mainly due to the loss of volatile elements such as tin or sulfur. In this work, we investigate how the additional step of sulfurization at reduced temperatures affects the quality and performance of CZTSSe based solar cells. A comprehensive structural analysis using conventional and high resolution XRD as well as Raman spectroscopy revealed that the highest CZTSSe material quality with the lowest structural disorder and defect densities was obtained from the CZTS films pre-sulfurized at 420 °C. Furthermore, we demonstrate the possibility of using Sb2Se3 as a buffer layer in the superstrate configuration of CZTSSe solar cells, which is possible alternative to replace commonly employed toxic CdS as a buffer layer. We show that the additional low-temperature selenization process and the successful use of Sb2Se3 as a buffer layer could improve the performance of CZTSSe-based solar cells by up to 3.48%, with an average efficiency of 3.1%.
ABSTRACT
Co-encapsulated PPI dendrimer with 64 functional groups (G5-generation) on periphery was synthesized. The modeled PPI dendrimer-like structure composed of 4 and 6 terminal flexible chains displays empty spaces between chains on periphery. Obtained occupation area on periphery is 1.0-3.0 nm2 where could be most probable location place of Co nanoparticle. The modeled structure displays that periphery of the PPI dendrimer is rich of oxygen atoms. The influence of oxygen on the stability of Co2O(m) and Co6O(m) (m = 1-7) clusters were studied. Calculations results demonstrate that higher oxidation rate enhances the stability of Co-O clusters.