Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 62: Poster II: Photovoltaics and Organic Semiconductors
HL 62.26: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D2
Photoelectric characterization of Cu(In,Ga)S2 Photovoltaic Devices with Varying Ga-Content — •Julia Riediger1, Jan Keller1, Jörg Ohland1, Martin Knipper1, Ingo Riedel1, Jürgen Parisi1, Roland Mainz2, Saoussen Merdes2, and Alexander Meeder3 — 1Uni Oldenburg — 2Helmholtz-Zentrum Berlin für Materialien und Energie Berlin GmbH — 3SULFURCELL Solartechnik GmbH
An increased efficiency of CuInS2-based solar cells is expected for absorber films doped with gallium which enlarges the band gap and therefore the open circuit voltage (VOC). We investigated Cu(In,Ga)S2 solar cells prepared under different rapid thermal processing (RTP) conditions. Depending on the RTP temperature profile, the films exhibit CuInS2/CuGaS2 (top/bottom) segregation which is detrimental for a large VOC. Solar cells prepared with different RTP-temperatures were investigated by temperature-/illumination-dependent current-voltage measurements (IV(T)), external quantum efficiency (EQE) and admittance spectroscopy (AS). Only precursors sulfurized at sufficiently high temperatures exhibited the desired interdiffusion of the segregated CuInS2/CuGaS2 system. The activation energies derived from IV(T) measurements suggest carrier losses due to interface recombination. The current collection in cells with substantial CuInS2/CuGaS2 segregation is limited over a wide temperature range up to 300K whereas the photocurrent is independent of temperature for T>200K. Admittance spectroscopy revealed a set of defect states, each of them representing different response to variation of the RTP process.