Correlation Between Chemical Composition and Efficiency of Cu2ZnSnS4 Solar Cells Prepared by a Solution Process

Abstract

Solution-based Cu2ZnSnS4 (CZTS) solar cells are attracting a lot of attention as a strong alternative to vacuum-based CZTS solar cells owing to their simple and low-cost process, large area deposition, and so on. Typically, the solution-based process consists of two steps: coating with precursor solution and annealing of the precursor films. Unlike vacuum-based deposition, the precursor solution contains unnecessary elements in order to form high quality precursor films, and thus, the precise control of the chemical composition of CZTS absorbers is essential for achieving highly efficient CZTS solar cells. In this work, we have investigated the correlation between chemical composition and efficiency of CZTS solar cells prepared by a spin coating method. The composition of the CZTS precursor solution is controlled in order to obtain optimized chemical composition of CZTS absorbers. Pre-annealing of CZTS precursor films is also varied to confirm the effect of thermal treatment on the chemical composition of CZTS absorbers. Due to the different thermal decomposition behaviors of metal precursors in CZTS precursor solutions, the chemical composition of CZTS absorbers are considerably affected by the pre-annealing temperature. The efficiency of CZTS solar cells is closely related to the chemical composition of CZTS absorbers and the CZTS solar cell with Cu/(Zn+Sn) = 0.75 and Zn/Sn = 1.10 exhibited JSC, VOC, FF, and efficiency of 0.58 V, 17.28 mA/cm2, 52.1%, and 5.18%, respectively. Copyright © 2016 American Scientific Publishers All rights reserved.