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Identifying the Impact of Surface Recombination at Electrodes in Organic Solar Cells by Means of Electroluminescence and Modeling
Author(s) -
Reinhardt Jens,
Grein Maria,
Bühler Christian,
Schubert Martin,
Würfel Uli
Publication year - 2014
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201400081
Subject(s) - materials science , electroluminescence , recombination , optoelectronics , electrode , photoactive layer , polymer solar cell , selectivity , heterojunction , signal (programming language) , organic solar cell , solar cell , chemical physics , molecular physics , layer (electronics) , nanotechnology , physics , chemistry , composite material , polymer , biochemistry , computer science , gene , programming language , catalysis
This work reports on combining current‐voltage characteristics, electroluminescence (EL) measurements, and modeling to identify the selectivity of the electrodes in bulk‐heterojunction organic solar cells. Devices with the same photoactive layer but different contact materials are compared and the impact of surface recombination at the contacts on their performance is determined. The open‐circuit voltage, V OC , depends strongly on the selectivity of the electrodes and it is observed that the EL signal of cells with lower V OC is dramatically reduced. This is ascribed to an enhanced rate of surface recombination, which is a non‐radiative recombination pathway and does therefore not contribute to the EL yield. In addition, these cells have a lower current in forward direction despite the fact that the surface recombination occurs in addition to the recombination in the bulk. A theoretical model was set up and in the corresponding numerical simulations all three findings (lower V OC , strongly reduced EL signal and lower forward current) could be clearly reproduced by varying just one single parameter which determines the selectivity of the electrode.