Abstract
A comparative study with focusing on carrier recombination properties in Cu2ZnSn(S,Se)4 (CZTSSe) and the CuInGaSe2 (CIGS) solar cells has been carried out. For this purpose, electroluminescence (EL) and also bias-dependent time resolved photoluminescence (TRPL) using femtosecond (fs) laser source were performed. For the similar forward current density, the EL-intensity of the CZTSSe sample was obtained significantly lower than that of the CIGS sample. Primarily, it can be attributed to the existence of excess amount of non-radiative recombination center in the CZTSSe, and/or CZTSSe/CdS interface comparing to that of CIGS sample. In case of CIGS sample, TRPL decay time was found to increase with the application of forward-bias. This can be attributed to the reduced charge separation rate resulting from the reduced electric-field at the junction. However, in CZTSSe sample, TRPL decay time has been found almost independent under the forward and reverse-bias conditions. This phenomenon indicates that the charge recombination rate strongly dominates over the charge separation rate across the junction of the CZTSSe sample. Finally, temperature dependent VOC suggests that interface related recombination in the CZTSSe solar cell structure might be one of the major factors that affect EL-intensity and also, TRPL decay curves.
Highlights
INTRODUCTIONPhotoluminescence (PL) spectroscopy is a widely used technique to study carrier recombination process in the CIGS materials as well as CZTSSe.[15,16,17,18,19,20,21] to investigate the junction quality of the semiconductors, electroluminescence (EL) proves to be useful.[22,23,24,25] EL-spectroscopy the principle of which is the exact inverse of the photovoltaic principle has never been used for CZTSSe material systems so far, there have been some reports for CIGS materials.[22,23] In the present study we have compared the charge carrier recombination process across the junction regions of CZTSSe and highly efficient CIGS solar cells
The second generation thin film solar cells based on chalcopyrite Cu(In,Ga)Se2 (CIGS) are already in the commercial stage
EL spectra measured at RT for the CIGS and the CZTSSe devices are presented in the Fig. 1(a) and 1(b), respectively
Summary
Photoluminescence (PL) spectroscopy is a widely used technique to study carrier recombination process in the CIGS materials as well as CZTSSe.[15,16,17,18,19,20,21] to investigate the junction quality of the semiconductors, electroluminescence (EL) proves to be useful.[22,23,24,25] EL-spectroscopy the principle of which is the exact inverse of the photovoltaic principle has never been used for CZTSSe material systems so far, there have been some reports for CIGS materials.[22,23] In the present study we have compared the charge carrier recombination process across the junction regions of CZTSSe and highly efficient CIGS solar cells For this purpose, room temperature EL and time resolved photoluminescence (TRPL) under different external bias have been investigated. A combined study of the EL and TRPL is crucial to understand the complete carrier recombination mechanism of both the CIGS and the CZTSSe material
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