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Proceedings Paper

Optical properties of low bandgap copolymer PTB7 for organic photovoltaic applications
Author(s): Uyen Huynh; Tek Basel; Tao Xu; Luyao Lu; Tianyue Zheng; Luping Yu; Valy Vardeny
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Paper Abstract

We used both cw and transient spectroscopies for studying the optical properties and photoexcitations in the low bandgap copolymer PTB7 that has been used in organic photovoltaic applications (OPV). Surprisingly we observed two primary photoexcitations that are generated within ~150 fs (our time resolution); we identify them as singlet exciton (S1) and triplet-pair (1TT). The singlet exciton has been considered to be the only primary photoexcitation in regular π-conjugated polymers and is related with a transient absorption band that peaks at an energy value close to the exciton binding energy (~0.4 eV in PTB7). The TT pair is a novel photoexcitation species in low band-gap π-conjugated copolymers. It has an absorption band close to that of isolated triplet exciton, and may readily dissociate at the donoracceptor interfaces in the PTB7/fullerene blend. This finding may explain the underlying mechanism for the high obtained power conversion efficiency in OPV devices based on the PTB7 copolymer.

Paper Details

Date Published: 9 September 2014
PDF: 7 pages
Proc. SPIE 9165, Physical Chemistry of Interfaces and Nanomaterials XIII, 91650Z (9 September 2014); doi: 10.1117/12.2064083
Show Author Affiliations
Uyen Huynh, The Univ. of Utah (United States)
Tek Basel, The Univ. of Utah (United States)
Tao Xu, The Univ. of Chicago (United States)
Luyao Lu, The Univ. of Chicago (United States)
Tianyue Zheng, The Univ. of Chicago (United States)
Luping Yu, The Univ. of Chicago (United States)
Valy Vardeny, The Univ. of Utah (United States)

Published in SPIE Proceedings Vol. 9165:
Physical Chemistry of Interfaces and Nanomaterials XIII
Natalie Banerji; Sophia C. Hayes; Carlos Silva, Editor(s)

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