Fabricating Cu2ZnSnS4, Cu2ZnSn(S,Se)4 and CuIn(S,Se)2 light-absorbing thin films for low-cost solar devices.

Vaishnavi Raja, The University of Western Ontario

Abstract

In this thesis, Cu₂ZnSnS₄ (CZTS), Cu₂ZnSn(S,Se)₄ (CZTSSe) and CuIn(S,Se)₂ (CISSe) thin-films have been optimized to use as the key light-absorbing and conversion layer for solar cells. CZTS nanocrystals (NCs) were solvothermally synthesized, etched with acetic acid and structurally analyzed using synchrotron spectroscopy. Electrodeposited CZTSSe films showed a non-ideal increase in sulfur with lower selenization temperature and post-process etching. Compositional studies of electrodeposited CISSe films confirmed the decrease in selenium after the acetic acid etching. Through PECMs and other conventional characterization techniques, it was determined that non-etched CZTSSe and CISSe solar devices performed better than their etched counterparts, achieving efficiencies of 5.3% and 2.1%, respectively. In contrast, the results of the CZTS NCs achieved a higher efficiency for the etched device at 6.5%. In the end, electrodeposition proved to be a cheaper, more replicable technique, while CZTSSe demonstrated to be the most cost-effective light-absorber-layer for efficient solar cells.