Barrierless slow dissociation of photogenerated charge pairs in high-performance polymer-fullerene solar cells

Dimali A. Vithanage, Andrew B. Matheson, Vytenis Pranculis, Gordon J. Hedley, Scott J. Pearson, Vidmantas Gulbinas, Ifor D. W. Samuel, Arvydas Ruseckas

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)
25 Downloads (Pure)

Abstract

Broadband transient absorption spectroscopy is combined with ultrafast carrier drift measurements to study dissociation of photogenerated charge pairs in efficient photovoltaic blends of the electron donating polymer PTB7 with the acceptor PC71BM. A high ensemble-average mobility sum of electrons and holes is observed which is independent of applied electric field above 12 V/μm and indicates nearly barrier-less pair dissociation at room temperature on a picosecond time scale. High efficiency of pair dissociation in this material is achieved by a combination of high electron mobility in fullerene clusters and hole delocalization along the polymer chain which increases by 30% during dissociation. Our results suggest a predominantly diffusive charge pair dissociation mechanism which requires persistent mobility of both carriers and preferably some delocalization of at least one of them.
Original languageEnglish
Pages (from-to)14060-14065
Number of pages6
JournalJournal of Physical Chemistry C
Volume121
Issue number26
Early online date1 Jun 2017
DOIs
Publication statusPublished - 6 Jul 2017

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