Molecular weight dependent bimolecular recombination in organic solar cells

Bronson Philippa; Martin Stolterfoht; Ronald D White; Marrapan Velusamy; Paul L Burn; Paul Meredith; Almantas Pivrikas

doi:10.1063/1.4891369

Molecular weight dependent bimolecular recombination in organic solar cells

J Chem Phys. 2014 Aug 7;141(5):054903. doi: 10.1063/1.4891369.

Authors

Bronson Philippa¹, Martin Stolterfoht², Ronald D White¹, Marrapan Velusamy², Paul L Burn², Paul Meredith², Almantas Pivrikas²

Affiliations

¹ College of Science, Technology and Engineering, James Cook University, Townsville 4811, Australia.
² Centre for Organic Photonics and Electronics (COPE), School of Chemistry and Molecular Biosciences and School of Mathematics and Physics, The University of Queensland, Brisbane 4072, Australia.

PMID: 25106609
DOI: 10.1063/1.4891369

Abstract

Charge carrier recombination is studied in operational organic solar cells made from the polymer:fullerene system PCDTBT:PC71BM (poly[N-9''-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)]: [6,6]-phenyl-C70-butyric acid methyl ester). A newly developed technique High Intensity Resistance dependent PhotoVoltage is presented for reliably quantifying the bimolecular recombination coefficient independently of variations in experimental conditions, thereby resolving key limitations of previous experimental approaches. Experiments are performed on solar cells of varying thicknesses and varying polymeric molecular weights. It is shown that solar cells made from low molecular weight PCDTBT exhibit Langevin recombination, whereas suppressed (non-Langevin) recombination is found in solar cells made with high molecular weight PCDTBT.