Determining the optimum morphology in high-performance polymer-fullerene organic photovoltaic cells

Hedley, G. J. , Ward, A. J., Alekseev, A. , Howells, C. T., Martins, E. R., Serrano, L. A., Cooke, G. , Ruseckas, A. and Samuel, I. D.W. (2013) Determining the optimum morphology in high-performance polymer-fullerene organic photovoltaic cells. Nature Communications, 4, 2867. (doi:10.1038/ncomms3867) (PMID:24343223) (PMCID:PMC3905772)

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Abstract

The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM. We show that optimized blends consist of elongated fullerene-rich and polymer-rich fibre-like domains, which are 10–50 nm wide and 200–400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion that helps in the extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene domains show a much lower efficiency of charge extraction of ~45%, which is attributed to poor electron and hole transport. Our results show that the formation of narrow and elongated domains is desirable for efficient bulk heterojunction solar cells.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Serrano Gonzalez, Mr Luis and Alekseev, Dr Alexander and Hedley, Dr Gordon and Cooke, Professor Graeme
Authors: Hedley, G. J., Ward, A. J., Alekseev, A., Howells, C. T., Martins, E. R., Serrano, L. A., Cooke, G., Ruseckas, A., and Samuel, I. D.W.
College/School:College of Science and Engineering > School of Chemistry
College of Science and Engineering > School of Physics and Astronomy
Journal Name:Nature Communications
ISSN:2041-1723
ISSN (Online):2041-1723
Copyright Holders:Copyright © 2013 Hedley, G.J. et al.
First Published:First published in Nature Communications 4:2867
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
551241Ageing of Printable Polymer Solar CellsJoachim LoosEngineering & Physical Sciences Research Council (EPSRC)EP/I013288/1P&A - PHYSICS & ASTRONOMY