Dresden 2006 – scientific programme

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HL: Halbleiterphysik

HL 32: Photovoltaic

HL 32.3: Talk

Wednesday, March 29, 2006, 15:00–15:15, BEY 118

Electronic Metastabilities in Cu(In,Ga)Se₂ Solar Cells — •Michael Reuter, Julian Mattheis, and Uwe Rau — Institut für Physikalische Elektronik, Pfaffenwaldring 47, D-70569 Stuttgart, Germany

Due to metastable electronic states, Cu(In,Ga)Se₂ solar cells show an electrical degeneration after being exposed to reverse voltage in the dark. While the degeneration effect first results in the shift of the dark current voltage characteristic towards larger voltages, the shift is reversed for prolonged degrading duration. This finding indicates that two competing processes with different time constants are involved in the mechanism leading to the observed metastable behavior. Subsequent illumination experiments reveal an increase of the open-circuit voltage V_OC under illumination with a power density of 100 mW/cm² and a decrease of V_OC under reduced illumination with 1 mW/cm². This intensity dependence of the change in V_OC supports the notion of two competing processes being involved in the creation and annihilation of metastable states. It points out that the injection level of minority carriers decides about whichever process will be dominant.