Spectroscopic ellipsometry studies of In₂S₃top window and Mo back contacts in chalcopyrite photovoltaics technology

Abstract

Abstract Spectroscopic ellipsometry (SE) was used to characterize the conventional back contact layer (Mo) as well as a novel top window layer (In 2 S 3 ) for use in chalcopyrite photovoltaics technology. For the Mo back contact, in‐situ SE measurements of thin films magnetron sputtered onto glass enabled determination of ε at different thicknesses during growth. The observed strong variations could be understood on the basis of a Drude relaxation time that varies with the Mo film thickness. For the In 2 S 3 window layer, ex‐situ SE measurements showed critical point structures at 2.77±0.08 eV, 4.92±0.005 eV, and 5.64 ± 0.005 eV, as well as an absorption tail with an onset near 1.9 eV. A comparison of the solar cell performance in simulations using either In 2 S 3 or conventional CdS revealed similar quantum efficiencies irrespective of the selected window layer. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)