Influence of blend ratio and processing additive on free carrier yield and mobility in PTB7:PC71BM photovoltaic solar cells

Pranculis, V., Ruseckas, A., Vithanage, D. A., Hedley, G. J. , Samuel, I. D.W. and Gulbinas, V. (2016) Influence of blend ratio and processing additive on free carrier yield and mobility in PTB7:PC71BM photovoltaic solar cells. Journal of Physical Chemistry C, 120(18), pp. 9588-9594. (doi: 10.1021/acs.jpcc.6b01548) (PMID:27293495) (PMCID:PMC4897731)

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Abstract

Charge separation and extraction dynamics were investigated in high-performance bulk heterojunction solar cells made from the polymer PTB7 and the soluble fullerene PC71BM on a broad time scale from subpicosecond to microseconds using ultrafast optical probing of carrier drift and the integral-mode photocurrent measurements. We show that the short circuit current is determined by the separation of charge pairs into free carriers, which is strongly influenced by blend composition. This separation is found to be efficient in fullerene-rich blends where a high electron mobility of >0.1 cm2 V–1 s–1 is observed in the first 10 ps after excitation. Morphology optimization using the solvent additive 1,8-diiodooctane (DIO) doubles the charge pair separation efficiency and the short-circuit current. Carrier extraction at low internal electric field is slightly faster from the cells prepared with DIO, which can reduce recombination losses and enhance a fill factor.

Item Type:Articles
Additional Information:This work was supported by the Research Council of Lithuania (Project No. MIP-85/2015), the Engineering and Physical Sciences Research Council of the UK (Grant Nos. EP/ J009016/1 and EP/L012294/1), and the European Research Council of the European Union (Grant No. 321305). I.D.W.S. also acknowledges support from a Royal Society Wolfson Research Merit Award. D.A.V. is grateful to Supergen SuperSolar Hub for the travel grant.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Hedley, Dr Gordon
Authors: Pranculis, V., Ruseckas, A., Vithanage, D. A., Hedley, G. J., Samuel, I. D.W., and Gulbinas, V.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Physical Chemistry C
Publisher:American Chemical Society
ISSN:1932-7447
ISSN (Online):1932-7455
Published Online:22 April 2016
Copyright Holders:Copyright © 2016 American Chemical Society
First Published:First published in Journal of Physical Chemistry C 120:9588 9594
Publisher Policy:Reproduced under a Creative Commons License

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