| 초록 |
Renewable energy sources, including solar photovoltaic (PV) energy, solar thermal energy, and biomass conversion energy, must be developed to meet the challenges of climate change. Among these energy sources, PV energy, which has the potential to convert an infinite amount of sunlight into solar electricity, can be used in everyday life if a high energy density can be achieved at a low cost and with a high power conversion efficiency (PCE). Of the many inorganic PV materials that have been considered for use in low-cost PV devices,2 thin film solar cells based on Cu2ZnSn(S,Se)4 (CZTSSe) and related materials have drawn significant interest in the context of PV technology because they use Earth-abundant elements and have useful band gap energies (Eg) of 1.0–1.5 eV and absorption coefficients exceeding 104 cm-1. However, compared with CdTe, which has a PCE of 21.5%, and CIGS, which has a PCE of 21.7%, CZTSSe, which has a PCE of 12.7%, must be further improved. To improve the efficiency of a CZTSSe solar cell, it is important to minimize current and voltage losses. To do so, the grain crystallinity must be improved; the formation of secondary phases must be suppressed; and the presence of defects, the Na content, and the band gap in the absorber layer must be controlled. In this study, we investigate the electrical, structural, and optical properties of CZTSSe thin films grown by a modified sulfo-selenization process from copper-poor and zinc-rich precursor metallic stacks prepared by sputtering. A series of new record CZTSSe devices are reported with the highest PCE at the 13% level. |
