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Facile Monitoring of Fullerene Crystallization in Polymer Solar Cell Blends by UV–vis Spectroscopy
Author(s) -
Lindqvist Camilla,
Wang Ergang,
Andersson Mats R.,
Müller Christian
Publication year - 2014
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.201300717
Subject(s) - fullerene , materials science , crystallization , polymer , glass transition , chemical engineering , polymer solar cell , organic solar cell , thermal stability , crystallinity , annealing (glass) , thiophene , spectroscopy , polymer chemistry , micrometer , solar cell , analytical chemistry (journal) , optoelectronics , organic chemistry , chemistry , optics , composite material , physics , quantum mechanics , engineering
A simple technique is demonstrated based on UV–vis spectroscopy that permits the onset of fullerene crystallization to be monitored in polymer:fullerene bulk‐heterojunction blends. The growth of fullerene crystals only occurs during thermal annealing above the glass transition temperature ( T g ) of the blend. Light scattering due to the presence of micrometer‐sized fullerene crystals reduces the apparent transmittance, which can serve as a clear indicator for the upper limit of the T g . This principle is used to deduce this critical parameter for two high‐performance photovoltaic blends that are based on a thiophene–quinoxaline and a thiophene–isoindigo copolymer, respectively. High T g s of 115 and 145 °C promise good thermal stability.