Back surface band gap gradings in Cu(In,Ga)Se-2 solar cells

We fabricate and analyse Cu(In,Ga)Se-2-based solar cells which have a grade d band gap by an increased Ga content towards the Mo back contact. The open circuit voltage and the short circuit current strongly improve with the ba nd gap grading. Electronic device analysis reveals that the open circuit vo ltage increase is directly related to the increased band gap energy at the back surface. We interpret the obtained results to a large extent as reduce d back contact recombination by the introduction of an increased band gap c lose to the back contact. (C) 2001 Elsevier Science B.V. All rights reserve d.