Continuous wave solid phase laser annealing of single-pot electrodeposited CuInSe2 thin films: Effects of Cu/In stoichiometry

Abstract

CuInSe2 (CISe) is a prototype material for the I–III–VI chalcopyrites such as Cu(In,Ga)(S,Se)2 (CIGSSe) used as absorber layers in thin film photovoltaic cells. These thin film photovoltaic absorber layers are primarily synthesized by vacuum-based techniques in manufacturing. In this work, we investigate non-vacuum film synthesis by electrochemical deposition of CISe from a single bath followed by continuous wave laser annealing (CWLA) using a 1064 nm laser. We find that parameters exist for near-infrared CWLA which result in structural changes without melting and dewetting of the films. While Cu-poor samples show only about 40% reduction in the full width at half maximum (FWHM) of the respective x-ray diffraction (XRD) peaks, identically treated Cu-rich samples indicate a FWHM reduction of more than 70% in the XRD and Raman scattering data for irradiation at 50 W/cm2. This study demonstrates that an entirely solid-phase annealing path driven by intense illumination exists for chalopyrite phase formation and crystallization from electrodeposited CISe thin films.