Performance analysis of CuIn 1-x Ga x S 2 (CIGS2)thin film solar cells based on semiconductor properties

Abstract

CuIn_1-xGa_xS₂ (CIGS2) has a bandgap of ~1.5 eV making it an ideal candidate for space applications. CIGS2 thin films were prepared by sulfurizing CuGa/In precursor on Mo-coated glass/ stainless steel (SS) substrates in N₂:H₂S (4% or 8%) mixture at 475°C. PV parameters measured under AM1.5 conditions at NREL were as follows: the first cell on stainless steel substrate, V_oc = 763.3 mV, J_sc = 20.26 mA/cm², FF = 67.04% and η = 10.4% and for the second cell on Mo-coated glass substrate, Voc = 830.5 mV, Jsc = 20.88 mA/cm², FF = 69.13% and η = 11.99%. A detailed comparative study of PV parameter of the two cells showed that the increase in the efficiency from 10.4% to 11.99% was made possible by an increase of shunt resistance R_p in the dark from 1160 Ω-cm² to 2500 Ω-cm²; a slight reduction of series resistance Rs; and a reduction of the diode factor, A and reverse saturation current density, J_o respectively from ~2.1 and ~2.6x10^-8 A cm^-2 to ~1.72 and ~1.41x10^-10 A cm^-2.