Effects of side chain isomerism on the physical and photovoltaic properties of indacenodithieno[3,2-b]thiophene–quinoxaline copolymers: toward a side chain design for enhanced photovoltaic performance
Artikel i vetenskaplig tidskrift, 2014

Four new D–A polymers PIDTT-Q-p, PIDTT-Q-m, PIDTT-QF-p and PIDTT-QF-m, using indacenodithieno[3,2-b]thiophene (IDTT) as an electron-rich unit and quinoxaline (Q) as an electron-deficient unit, were synthesized via a Pd-catalyzed Stille polymerization. The side chains on the pendant phenyl rings of IDTT were varied from the para- to the meta-position, and the effect of the inclusion of fluorine on the quinoxaline unit was simultaneously investigated. The influence on the optical and electrochemical properties, film topography and photovoltaic properties of the four copolymers were thoroughly examined via a range of techniques. The inductively electron-withdrawing properties of the fluorine atoms result in a decrease of the highest occupied molecular orbital (HOMO) energy levels. The effect of meta-substitution on the PIDTT-Q-m polymer leads to good solubility and in turn higher molecular weight. More importantly, it exhibits optimal morphological properties in the PIDTT-Q-m/PC71BM blends. As a result, the corresponding solar cells (ITO/PEDOT:PSS/polymer:PC71BM/LiF/Al) attain the best power conversion efficiency (PCE) of 6.8%. The structure–property correlations demonstrate that the meta-alkyl-phenyl substituted IDTT unit is a promising building block for efficient organic photovoltaic materials. This result also extends our strategy with regards to side chain isomerism of IDTT-based copolymers for enhanced photovoltaic performance.

Författare

Xiaofeng Xu

Chalmers, Kemi- och bioteknik, Polymerteknologi

Zhaojun Li

Chalmers, Kemi- och bioteknik, Polymerteknologi

Olof Bäcke

Chalmers, Teknisk fysik, Eva Olsson Group

Kim Bini

Chalmers, Kemi- och bioteknik, Polymerteknologi

David James

Chalmers, Kemi- och bioteknik, Polymerteknologi

Eva Olsson

Chalmers, Teknisk fysik, Eva Olsson Group

Mats Andersson

Chalmers, Kemi- och bioteknik, Polymerteknologi

Ergang Wang

Chalmers, Kemi- och bioteknik, Polymerteknologi

Journal of Materials Chemistry

0959-9428 (ISSN) 1364-5501 (eISSN)

Vol. 2 18988-18997

SUstainable Novel FLexible Organic Watts Efficiently Reliable (SUNFLOWER)

Europeiska kommissionen (FP7), 2011-10-01 -- 2016-03-31.

Ämneskategorier

Kemi

DOI

10.1039/C4TA04102J