Regensburg 2010 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 4: Photovoltaics I: mainly CIGS
HL 4.3: Talk
Monday, March 22, 2010, 10:45–11:00, H15
Characterisation of CuInSe2-based solar cells with different buffer layers — •Anton Werth1, Jörg Ohland1, Ingo Riedel1, Jürgen Parisi1, and Juan Rechid2 — 1Abteilung EHF, Institiut für Physik, Carl von Ossietzky Universität, Carl-von-Ossietzky-Straße 9-11, D-26129 Oldenburg — 2CIS Solartechnik GmbH & Co. KG, c/o Aurubis AG Hovestr. 50 20539 Hamburg
The optoelectronic properties of the buffer layer in chalcopyrite solar cells may present strong efficiency limitation due to parasitic absorption, interface states and band discontinuities in respect of the light absorber. In this work we investigated CuInSe2-based (CIS) solar cells processed on flexible steel substrates with In2S3 and CdS buffer layers by means of temperature dependent current-voltage (J-V) measurements at varying illumination intensity and external quantum efficiency (EQE) measurements. Under illumination the J-V curves of both cell types exhibit distinct "s"-shape non-ideality (roll over) at temperatures below 260K. The occurrence of the "s"-shape in the 4th and/or 1st quadrant is explained by an heuristic model which relates the band discontinuity being present at the buffer CIS interface to limitation of the minority carrier extraction and injection. Further, we employed the suns-Voc method to extract the diode parameters saturation current and diode ideality from the J-V characteristics under illumination (small effect of series resistance) in order to identify clues on dominant surface or bulk recombination. We conclude that interface recombination is less dominant in the investigated samples independent of the used buffer material.