Lateral variations of optoelectronic quality of Cu(In1-xGax)Se2 in the submicron-scale

Optoelectronic properties of Cu(In1-xGax)Se2 (CIGSe) have been studied by confocal microscopic photoluminescence (PL) with lateral submicron resolution. The lateral patterns of PL-yields, varying by factors of up to 10 between regimes with low and high emission, exhibit structures in the length scale of some micrometers (3-10 μm) whereas geometrical sizes of individual grains are in the 1-μm range or below. In addition to the local PL-variation, we observe that the geometrical extension of PL-patterns depend on excitation flux, that spectral PL-shapes are varying with respect to different onset energies of the low-energy wings, signalizing different local band gaps, and that low-energy PL-wings get steeper with rise in excitation flux pointing towards potential fluctuations and their respective screening by photoexcited excess carriers.