Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 93: Photovoltaics (HL, jointly with CPP, O)

HL 93.6: Talk

Friday, March 15, 2013, 10:30–10:45, H2

Investigation of the s-shape caused by the hole selective layer in organic bulk heterojunction solar cells — •Lothar Sims^1,2, Ulrich Hörmann², René Kogler³, Roland Steim⁴, Wolfgang Brütting², and Pavel Schilinsky¹ — ¹Belectric OPV GmbH, Landgrabenstr. 94, 90443 Nürnberg — ²University of Augsburg, Institute of Physics, Universitätsstr. 1, 86135 Augsburg — ³Evonik Industries AG, Kirschenallee, 64293 Darmstadt — ⁴STORM Energy GmbH, Rathenauplatz 2, 90489 Nürnberg

During the operation period of an organic solar cell different failure mechanisms can occur which limit the lifetime of the device. Among these failure mechanisms the so called s-shape or second diode, where the current density-voltage (JV) curve bends towards the origin in the 4th quadrant, plays an important role. We investigated the origin of the s-shape caused by the hole selective layer (HSL) using N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-benzidine (TPD) coevaporated with different amounts of Dipyrazino[2,3-f:2',3'-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile (HATCN) as a model system. The low glass transition temperature of TPD allows investigating the impact of WF and mobility of the HSL on device performance and thus s-shape independently of each other. The observed JV-curves were simulated by solving the drift-diffusion, i.e. continuity and Poisson equations numerical via the program PC1D. While WF rather influences the open circuit voltage, mobility seems to be the reason for the s-shape. The results show that an accumulation of holes near the hole selective/semiconductor layer interface might be responsible for the observed s-shape.