PT Journal AU Zhang, Z Hetterich, M Lemmer, U Powalla, M Hoelscher, H TI Cross sections of operating Cu(In,Ga)Se2 thin-film solar cells under defined white light illumination analyzed by Kelvin probe force microscopy SO Applied physics letters PY 2013 BP 023903/1 EP 6 VL 102 IS 2 DI 10.1063/1.4775679 LA english ER