CuIn1−xGaxSe2‐based thin‐film solar cells by the selenization of sequentially evaporated metallic layers

Polycrystalline CuIn_1−xGa_xSe₂ (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 on the solar cells performance. An efficiency enhancement was obtained for Cu/(In+Ga) 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 an improvement of efficiency and V_OC. Furthermore, an 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 © 2005 John Wiley & Sons, Ltd.