Development of heterojunction CZTS based solar cell using solution based deposition methods

Abstract

The superstrate configuration of heterojunction thinfilm solar cell deposition was investigated using low cost solution based techniques. Commercially available SnO2:F coated glass was used as the front contact and superstarte, Cadmium Sulfide (CdS) as the n-type semiconductor and Copper Zinc Tin Sulfide (CZTS) as the p-type absorber layer. Chemical bath deposition method was utilized for CdS thin film fabrication and the CdS thin film with optimum properties was obtained at the conditions of 40oC-45oC temperature range and thickness variations were also apparent with the number of coatings applied and the change of fabrication time. The annealing temperature was found to be critical within the range of 180oC-220oC for the optimization of CdS bandgap, and grain growth and grain refining effects were apparent at higher temperatures. CdS thin films fabricated under optimum conditions have given a bandgap range of 2.30eV-2.50eV. CZTS layer fabrication was done using spin coating method and optimum conditions for CZTS layer fabrication was found to be 2000rpm-6000rpm spinning speed with 30 seconds of spin time, 38oC-42oC precursor solution temperature, 140oC-160oC drying temperature, and 280oC annealing temperature that promotes the formation of CZTS. The obtained CZTS layers have shown a bandgap in the range of 1.45eV to 1.55eV.