Identify the Origin of the Voc Deficit of Kestertie Solar Cells from the Two Reaction Paths Induced by Sn2+ and Sn4+ Precursors in DMSO Solution

摘要

The reaction paths and device characteristics of the two Cu2ZnSn(S,Se)4 absorbers fabricated from DMSO solution respectively using Sn^{2+ and Sn4+ as tin precursor were systematically investigated to identify the large voltage deficit issue that limits kesterite solar cell performance. Our results show Sn2+ precursor film took a multi-phase fusion reaction path and forms in a very defective surface whereas Sn4+ precursor film took a direct transformation reaction path and forms a uniform and less defective surface. The much larger Voc deficit of Sn2+ device mainly comes from the deep defect rich surface due to its unfavorable grain growth.}