2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) | 2019
Defect Analysis in CSS and Sputtered CdSexTe1-x Thin Films
Abstract
Defect analysis of CdSexTe1-x alloy films prepared via close space sublimation (CSS) and sputtering have been carried out utilizing low temperature photoluminescence (PL) spectroscopy. We observe defect emission at 1.31 eV in both CSS and sputtered films which red shifts with increasing temperature. Therefore, the 1.31 eV peak is assigned to recombination of an electron in the conduction band with a hole localized in an unidentified vacancy defect state. Unlike CdSexTe1-x, ~1.31 eV peak has been assigned to free-to-bound (FB) peak in polycrystalline CdTe by previous researchers. Our analysis shows that a small amount of Se incorporation into CdTe has been found to change the nature of dominant native defect. Furthermore, we observe the bound exciton peak at ~1.49 eV in both films while free exciton peak (1.52 eV) is absent in latter. The presence of a free excitonic peak in CSS film confirms its better crystallinity compared to the sputtered one. Identification of such defect states and their nature are crucial to improving the efficiency of CdTe based solar cells.