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Charge-Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition

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Title: Charge-Separation in Intermixed Polymer:PC70BM Photovoltaic Blends: Correlating Structural and Photophysical Length Scales as a Function of Blend Composition
Authors: Utzat, H
Dimitroy, SD
Wheeler, S
Collado-Fregoso, E
Tuladhar, PS
Schroeder, BC
McCulloch, I
Durrant, JR
Item Type: Journal Article
Abstract: A key challenge in achieving control over photocurrent generation by bulk-heterojunction organic solar cells is understanding how the morphology of the active layer impacts charge separation and in particular the separation dynamics within molecularly intermixed donor–acceptor domains versus the dynamics between phase-segregated domains. This paper addresses this issue by studying blends and devices of the amorphous silicon–indacenodithiophene polymer SiIDT-DTBT and the acceptor PC70BM. By changing the blend composition, we modulate the size and density of the pure and intermixed domains on the nanometer length scale. Laser spectroscopic studies show that these changes in morphology correlate quantitatively with the changes in charge separation dynamics on the nanosecond time scale and with device photocurrent densities. At low fullerene compositions, where only a single, molecularly intermixed polymer–fullerene phase is observed, photoexcitation results in a ∼ 30% charge loss from geminate polaron pair recombination, which is further studied via light intensity experiments showing that the radius of the polaron pairs in the intermixed phase is 3–5 nm. At high fullerene compositions (≥67%), where the intermixed domains are 1–3 nm and the pure fullerene phases reach ∼4 nm, the geminate recombination is suppressed by the reduction of the intermixed phase, making the fullerene domains accessible for electron escape.
Issue Date: 24-Apr-2017
Date of Acceptance: 1-Apr-2017
URI: http://hdl.handle.net/10044/1/49011
DOI: https://dx.doi.org/10.1021/acs.jpcc.7b02898
ISSN: 1932-7447
Publisher: American Chemical Society
Start Page: 9790
End Page: 9801
Journal / Book Title: JOURNAL OF PHYSICAL CHEMISTRY C
Volume: 121
Issue: 18
Copyright Statement: © 2017 American Chemical Society. This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, after peer review and technical editing by the publisher. To access the final edited and published work see https://dx.doi.org/10.1021/acs.jpcc.7b02898
Keywords: Science & Technology
Physical Sciences
Technology
Chemistry, Physical
Nanoscience & Nanotechnology
Materials Science, Multidisciplinary
Chemistry
Science & Technology - Other Topics
Materials Science
ORGANIC SOLAR-CELLS
BULK HETEROJUNCTIONS
CONJUGATED POLYMERS
POLYMER/FULLERENE BLENDS
QUANTUM EFFICIENCY
ELECTRON-ACCEPTORS
CARRIER GENERATION
EXCITON DIFFUSION
FULLERENE BLENDS
STATE DYNAMICS
Physical Chemistry
09 Engineering
03 Chemical Sciences
10 Technology
Publication Status: Published
Appears in Collections:Physics
Chemistry
Faculty of Natural Sciences



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