Time-Resolved Microphotoluminescence Study of Cu(In,Ga)Se2

The carrier recombination processes in Cu(In1-x,Ga-x)Se-2 (CIGS) thin films were investigated by time-resolved microscopic-photoluminescence (mu-PL) measurement at room temperature. For films with x = 45, the spatial distribution of the donor-acceptor pair luminescence is much larger than the grain size. The PL decay lifetime is directly correlated with the mu-PL intensity, but the spectral shape is identical regardless of the sample position. These results suggest that the nonuniform distribution of nonradiative recombination centers mainly affects the carrier recombination in CIGS thin films. At relatively high Ga concentrations (x >= 0.7), the spatial inhomogeneity in mu-PL intensity is enhanced and decay accelerated, suggesting an increase in the density of nonradiative recombination centers. Thus, suppression of nonradiative recombination is critical to enhancing the performance of CIGS-based solar cells. (C) 2011 The Japan Society of Applied Physics