Photoreflectance characteristics of chemical-bath-deposited-CdS layer in Cu(In,Ga)Se2 thin-film solar cells

The authors have characterized the CdS layer in Cu(In,Ga)Se2 thin-film solar cells using photoreflectance (PR) spectroscopy and investigated its influence on the photovoltaic performance. The CdS layer was fabricated by chemical bath deposition with various concentrations of ammonia (1.0–3.0 M), thiourea (0.025–0.1 M), and Cd-salt (0.0004–0.003 M) as well as various thicknesses (30–90 nm). The PR transition energy in CdS increased from 2.282 to 2.366 eV as the thiourea concentration increased from 1.0 to 3.0 M, whereas it decreased as the thickness of CdS increased. The conversion efficiency depended on neither the ammonia and the Cd-salt concentrations nor the thickness of CdS, whereas it changed from 14.72% to 15.81% as the thiourea concentration decreases from 3.0 to 1.0 M.