Widegap Cu InGa S2 thin film solar cells on transparent substrates

ABSTRACT We have previously demonstrated the potential of Cu In,Ga S2 CIGS for realizing high efficiency wide gap chalcopyrite based solar cells. CIGS absorber films were prepared by multi source evaporation using a Cu poor Cu rich deposition sequence onto soda lime glass substrates coated with different transparent conductive oxides TCOs . The Ga In ratio was adjusted for a band gap of more than 1.6 eV. The properties of films and cells are compared to those deposited onto standard glass Mo substrates. Films with reasonable morphology and good adhesion to the substrate were obtained on most of the investigated TCOs. Also, electrical and optical properties of the TCO typically did not deteriorate strongly during absorber preparation. Our best result so far is a cell with an efficiency of about 8 on indium tin oxide ITO . At an absorber band gap of 1.64 eV this cell exhibited an open circuit voltage of 775 mV, a fill factor of 55 and a short circuit current density of 18.6 mA cm2. To our knowledge, this is currently the best wide gap chalcopyrite based cell on a glass TCO substrate. The cell was slightly shunted but there were no indications for a non ohmic behavior of the ITO CIGS contact Keywords CuInS2 , Thin Film , TCO Transparent Conducting Oxide