Optical and electrical characterization of Cu(In,Ga)Se2 thin film solar cells with varied absorber layer thickness

Cu(In,Ga)S2 solar cells with different absorber layer thicknesses prepared by means of a three-stage co-evaporation process are investigated to determine the electrical losses depending on the absorber layer thickness. The absorber material is characterized by energy dispersive X-ray spectroscopy, time of flight secondary ion mass spectroscopy and optical transmission and reflectance measurements. The acceptor concentration is determined admittance spectroscopy in the range of 8.4 · 1015 cm− 3 to 3.8  · 1016 cm− 3. From external quantum efficiency and current-voltage-measurements combined with the determined absorption coefficient we attribute the losses in the short circuit current density to incomplete absorption.