Thin Solid Films, Vol.480, 259-263, 2005
Structural properties and quality of the photoexcited state in Cu(In1-xGax)Se-2 solar cell absorbers with lateral submicron resolution
We analyze the quality of the photoexcited state in Cu(In,Ga)Se-2 absorbers prepared under conditions similar to module pilot line production with different Ga-admixtures in terms of the splitting of the quasi-Fermi levels by confocal microscopic photoluminescence (PL) with submicron lateral resolution. The lateral luminescence patterns exhibit structures in the length scale of some micrometers (3-10 AM) which by far exceed the geometrical sizes of individual grains with diameters of 1 mu m or below, detected simultaneously by optical reflection, and by scans of atomic force microscopy (AFM). The luminescence yields recorded at (83-250) K and at about (10(4)-10(2)) air mass 1.5 (AM1.5)-equivalent photon fluxes show lateral alterations by factors (2-20) depending on Ga-content, excitation level, and temperature. From temperature and excitation regimes, we are able to extrapolate the lateral variations towards 300 K and AM 1.5-equivalent fluxes, and we translate PL-yields into lateral alterations of the splitting of quasi-Fermi-levels Delta(E-Fn-E-Fp) and of corresponding variations in maximum hypothetic open circuit voltages V-oc. (c) 2004 Elsevier B.V. All rights reserved.