Atomic layer deposition of In2O3 transparent conductive oxide layers for application in Cu(In,Ga)Se2 solar cells with different buffer layers

This contribution presents the development of atomic layer deposited (ALD) In2O3 films for utilization as transparent conductive oxide (TCO) layers in Cu(In,Ga)Se-2 (CIGSe) solar cells. The effects of ALD process parameters on the morphology and growth of In2O3 are studied and related to the electrical and optical properties of the films. Maintaining similar resistivity values compared to commonly used ZnO:Al (AZO) TCOs (rho = (5-7) x 10(-4) Omega cm), a superior mobility of mu approximate to 110 cm(2)/Vs could be achieved (more than five times higher than a ZnO:Al reference), which results in a significantly reduced parasitic optical absorption in the infrared region. Application of the optimized In2O3 layers in CIGSe solar cells with varying buffer layers (CdS and Zn1-xSnxOy (ZTO)) leads to a distinct improvement in short circuit current density J(sc) in both cases. While for solar cells containing the ZTO/In2O3 window structure, a drop in open-circuit voltage V-oc and a deterioration under illumination is observed, the TCO exchange (from AZO to In2O3) on CdS buffer layers results in an increase in V-oc without detectable light bias degradation. The efficiency eta of the best corresponding solar cells could be improved by about 1% absolute. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim