Ultrafast carrier dynamics in Cu(In,Ga)Se₂ thin films probed by femtosecond pump-probe spectroscopy

Opt Express. 2012 Jun 4;20(12):12675-81. doi: 10.1364/OE.20.012675.

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.

Publication types

  • Research Support, Non-U.S. Gov't