Doping of Sb into Cu2ZnSn(S,Se)4 absorber layer via Se&Sb2Se3 co-selenization strategy for enhancing open-circuit voltage of kesterite solar cells

Abstract

Kesterite-structured Cu2ZnSn(S,Se)4 (CZTSSe) thin film photovoltaics have attracted considerable attention in recent years because of its low-cost and eco-friendly raw material, as well as high theoretical conversion efficiency. However, its photovoltaic performance is hindered by large open-circuit voltage (VOC) deficiency due to the presence of intrinsic defects and defect clusters in the bulk of CZTSSe absorber films. The doping of extrinsic cation to the CZTSSe matrix was adopted as an effective strategy to ameliorate defect properties of the solar cell absorbers. Herein, a novel Se&Sb2Se3 co-selenization process was employed to introduce Sb into CZTSSe crystal lattice. The results reveal that Sb-doping plays an active role in the crystallization and grain growth of CZTSSe absorber layer. More importantly, one of the most seriously detrimental SnZn deep defect is effectively passivated, resulting in significantly reduced deep-level traps and band-tail states compared to Sb free devices. As a result, the power conversion efficiency of CZTSSe solar cell is increased significantly from 9.17% to 11.75%, with a VOC especially enlarged to 505 mV from 449 mV. This insight provides a deeper understanding for engineering the harmful Sn-related deep defects for future high-efficiency CZTSSe photovoltaic devices.

Progress and prospectives of solution-processed kesterite absorbers for photovoltaic applications

“…78 In addition to the above reports, Wu's group has developed strategies, such as alkali metal post-deposition treatment (PDT), supercritical carbon dioxide treatment, surface defect ordering and co-selenization, to improve device performance. [79][80][81]91 In addition, Cheng's group has also increased the efficiency of flexible CZTSSe solar cells to 10.24% using a pre-selenization process. 82 According to the above beneficial optimization strategy, the highest efficiency of CZTSSe devices was 12.54% manufactured by an amine-thiol solvent.…”

Defect-level trap optimization in Cu2ZnSn(S,Se)4 photovoltaic materials via Sb3+-doping for over 13% efficiency solar cells

“…At the selenization temperature of 555 °C, the saturated vapor pressure of the selenization temperature, an order of magnitude increase can even be achieved. 29,30 This process enables rapid penetration of Sb ions into the bottom layer and inhibits defect formation.…”