Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 12: Poster I

HL 12.2: Poster

Monday, March 8, 2004, 16:30–19:00, Poster A

Deep level transient spectroscopy on copper indium gallium diselenide thin film solar cells with different gallium content — •V. Mertens¹, R. Reineke-Koch², M. Köntges², and J. Parisi¹ — ¹University of Oldenburg, 26111 Oldenburg — ²Instiute for Solar Engery Research, 31860 Emmerthal

One approach to increase the open circuit voltage V_oc of Cu(In,Ga)Se₂ solar cells is to widen the bandgap E_g by using higher gallium contents than in the standard composition which has a gallium to gallium plus indium ratio (GGI) of about 0.28. However further investigations on these materials showed that their V_oc is lower than expected from the empirical relationship V_oc=E_g−0.5 V which holds for E_g≤1.3 eV. To understand more about the whole alloy system, we focused on the defects and the change in their characteristics with composition. For our measurements we use a home build deep level transient spectrometer based on a Boonton 7200B capacitance bridge. We investigated different samples covering the whole alloy range with different DLTS techniques as majority and minority carrier DLTS, reverse-bias pulsed DLTS. We found that the transients are poorly described by a sum of several monoexponential decays. Therefore other analyses were conducted to determine the underlying physical mechanism.