Influence of the reaction pathway on the defect concentration of Cu₂ZnSnSe₄ thin film solar cells by manipulation selenization temperature ramping

Much effort has been expended on controlling the point defects and eliminating the double-layer structures in the Cu₂ZnSnSe₄ (CZTSe) absorber layer of CZTSe solar cells to improve their efficiency. In this study, a sputtering technique was used to deposit Cu_xSe and Zn_xSn_1-x films as CZTSe precursors; moreover, the temperature of the low-temperature annealing process was controlled to create different reaction pathways towards the synthesis of CZTSe; this was done to study the effects of the temperature and the selected reaction pathway on the morphology of the CZTSe absorber layer and the concentration of the point defects. Moreover, several techniques, including X-ray diffraction analysis (XRD), Raman spectroscopy, photoluminescence (PL), UV–vis-NIR spectrometers, transmission electron microscopy (TEM), capacitance-voltage (C[sbnd]V) measurements, and energy-dispersive X-ray spectroscopy (EDS), were used to characterize the CZTSe thin films and CZTSe solar cells. It was discovered that manipulating the temperature of the low-temperature annealing process could be used to control which reaction pathway was followed to synthesise CZTSe, suppress Sn loss and the formation of the ZnSe phase, influence the morphology, structure, compositional uniformity and concentration of the point defects of the CZTSe films, and alter the thickness of the MoSe₂ layer. It is anticipated that this type of systematic study will provide insight into how point defects and the nanostructure of CZTSe materials affect the characteristics of solar cells; furthermore, the studies should inspire new approaches to solving the current limitations of CZTSe solar cells, thus promoting the future development of high-efficiency solar cells.