PV characterization of CIGS2 thin film solar cells

CuIn_1-xGa_xS₂ (CIGS2) thin films were prepared by sulfurization of CuGa/In precursor on Mo-coated glass substrates in Ar:H₂S(4%) mixture at 475°C. PV parameters of the best CIGS2 solar cells measured under AM 0 conditions at NASA GRC were as follows: V_oc=739 mV, J_sc=26.01 mA/cm² , FF=63.7%, and η=8.95%. Detailed current versus voltage and quantum efficiency analysis of ~9% (AM 0) efficient CIGS2 cells showed them to be normal, without serious limitations and some ways promising. Formation of a buried n⁺p homojunction probably due to Cd doping during CdS chemical bath deposition was inferred from enhancement of collection at low wavelengths under reverse bias. Such a junction is known to lead to high conversion efficiency. Values of series resistance Rs, shunt resistance Rp, diode factor A, and reverse saturation current Jo were ~0.6 Ω cm², ~1160 Ω cm², ~2.1 and ~2.6×168 A cm-2 respectively. Preparation of ~8% AM1.5 efficient CIGS2 thin-film solar cells on Mo-coated stainless steel foil substrates for ultra lightweight solar cells is described