Several groups have demonstrated high efficiency Cu2ZnSnSe4 (CZTSe), Cu2ZnSnS4 (CZTS) and Cu2ZnSn(SeS)4 (CZTSeS) solar cells. Especially the highest efficiency has been achieved via the solution-based CZTSeS cells by IBM. However, the power conversion efficiencies are still low as compared with the other solar cells because of the low open circuit voltage (Voc). Recently, improvement of the Voc in these solar cells by applying a hybrid buffer layer with combination of Cd-based and In-based buffer layers has been reported. The hybrid buffer is considered to drastically boost Voc, and previous reports have focused on Voc and Voc deficit (defined in Eg/q-Voc). In this study we confirm that the hybrid buffer layer can boost not only Voc but also Jsc in the CZTSeS solar cells made using a solution process. Specifically improvement of electrostatic potential fluctuation (opt) and bandgap fluctuation (g) which have a strong relation with the Voc was confirmed, which indicates that the hybrid buffer has a potential to improve the band tailing problem in the CZTS-based solar cells. Furthermore, based on external quantum efficiency (EQE) and drive-level capacitance profiling (DLCP) analyses, improvement of EQE in the long wavelength region by enhancement of depletion width (Xd) was revealed. Finally the efficiency (Eff) of 12.7% in-house measurement in IBM (12.3% certificated in Newport) in solution-based CZTSeS cells has been achieved by applying the hybrid buffer layer.
各種検索
サポート
ヘルプ