Device Postannealing Enabling over 12% Efficient Solution-Processed Cu<sub>2</sub> ZnSnS<sub>4</sub> Solar Cells with Cd<sup>2+</sup> Substitution.
basic_science · Level V
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- Record sourced from PubMed, PMID 32613674.
- Also identified by DOI 10.1002/adma.202000121.
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Abstract
Kesterite Cu<sub>2</sub> ZnSnS<sub>4</sub> is a promising photovoltaic material containing low-cost, earth-abundant, and stable semiconductor elements. However, the highest power conversion efficiency of thin-film solar cells based on Cu<sub>2</sub> ZnSnS<sub>4</sub> is only about 11% due to low open-circuit voltage and fill factor mainly caused by antisite defects and unfavorable heterojunction interface. In this work, a postannealing procedure is proposed to complete a Cd-alloyed Cu<sub>2</sub> ZnSnS<sub>4</sub> device. The postannealing to complete the device significantly enhances the performance of the indium tin oxide and promotes the moderate interdiffusion of elements between the layers in the device. As a result of the diffusion of Cu, Zn, In, and Sn, the interfacial electron and hole densities are improved, leading to the achievement of a suitable band alignment for carrier transport. The postannealing also reduces the interface traps and deep-level defects, contributing to decreased nonradiative recombination. Therefore, the open-circuit voltage and fill factor are both improved, and an efficiency over 12% for pure sulfide-based kesterite thin-film solar cells is obtained.