Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 15: Joint Session: Organic Semiconductors I: Solar Cells A

HL 15.4: Talk

Monday, March 14, 2011, 15:00–15:15, ZEU 222

Bias-Dependent Transient Absorption on Organic Solar Cells; Connection to Device Performance? — •Ian Howard, Ralf Mauer, Valentin Kam, Michael Meister, and Frédéric Laquai — Max Planck Forschungsgruppe für Organische Optoelektronik, Max-Planck-Institut für Polymerforschung, Mainz, Deutschland

We directly observe the bias dependence of charge-transfer state separation in organic bulk heterojunctions using in-situ transient absorption on operating organic solar cells. The effect of bias on charge-transfer state lifetime (< 2ns) is found to be minimal, however suppression of nongeminate recombination with bias on later timescales (>10 ns) is observed and explains the bias dependence of the photocurrent. The bias independence of charge-transfer state separation is directly applicable to interpreting organic solar cell performance under standard AM1.5 illumination. However, due to the differences in charge densities and dynamic versus steady-state behavior between pulsed measurements and standard operating conditions, the effects of bias on the suppression of nongeminate recombination are not simplistically transferable. We consider to what extent pulsed transient absorbtion techniques on devices can be used to reveal nongeminate recombination mechanisms in devices operating under standard illumination conditions.