Slow geminate-charge-pair recombination dynamics at polymer: Fullerene heterojunctions in efficient organic solar cells

We explore charge recombination dynamics at electron donor‐acceptor heterojunctions, formed between a semiconductor polymer (PCDTBT) and a fullerene derivative (PC70BM), by means of combined time‐resolved photoluminescence and transient absorption spectroscopies. Following prompt exciton dissociatio...

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Vydáno v:	Journal of polymer science. Part B, Polymer physics Ročník 50; číslo 20; s. 1395 - 1404
Hlavní autoři:	Provencher, Françoise, Sakowicz, Maciej, Brosseau, Colin-Nadeau, Latini, Gianluca, Beaupré, Serge, Leclerc, Mario, Reynolds, Luke X., Haque, Saif A., Leonelli, Richard, Silva, Carlos
Médium:	Journal Article
Jazyk:	angličtina
Vydáno:	Hoboken Wiley Subscription Services, Inc., A Wiley Company 15.10.2012 Wiley
Témata:	Application fields Applied sciences Charge charge-transfer excitons Derivatives Dynamics Energy Exact sciences and technology Excitation Fullerenes Heterojunctions materials science Natural energy organic solar cells Pathways Photovoltaic conversion physical chemistry physics polaron-pair recombination dynamics Polymer industry, paints, wood polymer science & technology semiconductor polymers Semiconductors Solar cells. Photoelectrochemical cells Solar energy Technology of polymers Terpolymer Fullerene compounds Solid solid interface Photoluminescence Organic solar cells Modeling Excitonic process Charge carrier recombination Optical properties Nitrogen heterocycle copolymer physics Aromatic copolymer Heterojunction physical chemistry materials science Carbazole derivative copolymer charge-transfer excitons Thiophene copolymer Experimental study polymer science & technology Luminescence decay semiconductor polymers Conjugated copolymer Kinetics polaron-pair recombination dynamics
ISSN:	0887-6266, 1099-0488
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Shrnutí:	We explore charge recombination dynamics at electron donor‐acceptor heterojunctions, formed between a semiconductor polymer (PCDTBT) and a fullerene derivative (PC70BM), by means of combined time‐resolved photoluminescence and transient absorption spectroscopies. Following prompt exciton dissociation across the heterojunction, a subset of bound electron‐hole pairs recombines with a temperature‐independent rate distribution spanning submicrosecond timescales to produce luminescent charge‐transfer excitons (CTX). At 14 K, this slow mechanism is the dominant geminate charge recombination pathway, whereas we also observe CTX emission on subnanosecond timescales at 293 K. We thus find that at these temperatures, a fraction of the initial charge‐pair population is trapped deeply such that they only recombine slowly over a broad distribution of timescales by quantum tunneling. We identify geminate polaron pairs (GPP) as a reservoir of long‐lived localized states that repopulate the CTX up to microsecond timescales. The observation of such distributed geminate‐charge recombination highlights the importance of the molecular nature of specific donor–acceptor electronic interactions in defining the relaxation pathways of trapped GPP. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 Charge‐transfer‐exciton recombination dynamics are probed over timescales orders of magnitude longer than has been previously reported for PCDTBT:PC70BM donor‐acceptor heterostructures. Delayed photoluminescence is attributed to slow generation of charge‐transfer excitons via tunneling from deeply trapped geminate polaron pairs. Using time‐resolved spectroscopic measurements at various temperatures and photophysical modeling, it is estimated that 16% of geminate recombination at room temperature originate from this slow mechanism.
Bibliografie:	NSERC ark:/67375/WNG-9WPZZ89C-6 istex:EC0096F03ABCAE215C8E5AEE4950B243148B7644 Canada Research Chair in Organic Semiconductor Materials ArticleID:POLB23139 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	0887-6266 1099-0488
DOI:	10.1002/polb.23139