CuIn1-xGaxSe2-based thinilm solar cells by the selenization of sequentially evaporated metallic layers

Polycrystalline CuIn1-xGaxSe2 (CIGS) thin films were deposited by the non-vacuum, near-atmospheric-pressure selenization of stacked metallic precursor layers. A study was carried out to investigate the influence of significant factors of the absorber oil the solar cells performance. An efficiency enhancement was obtained for Cu/(In + Go) atomic ratios between 0.93 and 0.95. The slope of the observed energy bandgap grading showed a strong influence on the V-OC and the short circuit current density J(SC). An increase of the Ga content in the active region of the absorber was achieved by the introduction of a thin Ga layer on the Mo back contact. This led to all improvement of efficiency and V-OC. Furthermore, all enhanced carrier collection was detected by quantum efficiency measurements when the absorber layer thickness was slightly decreased. Conversion efficiencies close to 10% have been obtained for these devices. Copyright (c) 2005 John Wiley & Sons, Ltd.