Chen SC, Liao YK, Chen HJ, Chen CH, Lai CH, Chueh YL, Kuo HC, Wu KH, Juang JY, Cheng SJ, Hsieh TP, Kobayashi T. Ultrafast carrier dynamics in Cu(In,Ga)Se₂ thin films probed by femtosecond pump-probe spectroscopy.
OPTICS EXPRESS 2012;
20:12675-12681. [PMID:
22714296 DOI:
10.1364/oe.20.012675]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ultrafast carrier dynamics in Cu(In,Ga)Se₂ films are investigated using femtosecond pump-probe spectroscopy. Samples prepared by direct sputtering and co-evaporation processes, which exhibited remarkably different crystalline structures and free carrier densities, were found to result in substantially different carrier relaxation and recombination mechanisms. For the sputtered CIGS films, electron-electron scattering and Auger recombination was observed, whereas for the co-evaporated CIGS films, bandgap renormalization accompanied by band filling effect and hot phonon relaxation was observed. The lifetime of defect-related recombination in the co-evaporated CIGS films is much longer than that in the direct-sputtered CIGS films, reflecting a better quality with higher energy conversion efficiency of the former.
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