Berlin 2012 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 38: Photovoltaics: CIGS and related Materials
HL 38.4: Talk
Tuesday, March 27, 2012, 12:00–12:15, ER 270
Investigation of defects in Cu(In,Ga)S2 and Cu(In,Ga)Se2 solar cells by space charge spectroscopy — •Julia Riediger1, Jörg Ohland1, Martin Knipper1, Jürgen Parisi1, Ingo Riedel1, and Alexander Meeder2 — 1Thin Film Photovoltaics, Energy- and Semiconductor Research Laboratory, University of Oldenburg, D-26111 Oldenburg — 2Soltecture GmbH, 12487 Berlin
If deep defect states in the absorber of a solar cell act as recombination centers, they may limit the carrier lifetime and thus the open circuit voltage. This is related to the defect’s activation energy and spatial position. In this study the defect landscape of chalcopyrite thin film solar cells with varied absorber composition was investigated by space charge spectroscopy. The absorber layer in Cu(In,Ga)S2 samples arises from rapid thermal process (RTP) in sulfur vapor while Cu(In,Ga)Se2 absorbers were processed via co-evaporation of the constituents. Several defect states were found by deep level spectroscopy (DLTS) and thermal admittance spectroscopy (TAS). With the knowledge of the defect activation energies we derived the spatial defect concentrations from (illuminated) capacitance-voltage (CV) measurements and discuss the results for both material systems. To identify the often discussed "N1" defect, the measurements were repeated after annealing and changes in the defect spectra were evaluated.