Annealing‐Induced Chemical Interaction at the Ag/In2O3:H Interface as Revealed by In Situ Photoelectron Spectroscopy

Abstract

AbstractHydrogen‐doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light‐emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency‐limiting mechanism, hard X‐ray photoelectron spectroscopy is employed to in‐situ monitor annealing‐induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex‐situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag‐ and In‐related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often‐reported deterioration.