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Copolymers of Cyclopentadithiophene and Electron‐Deficient Aromatic Units Designed for Photovoltaic Applications
Author(s) -
Bijleveld Johan C.,
Shahid Munazza,
Gilot Jan,
Wienk Martijn M.,
Janssen René A. J.
Publication year - 2009
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200900412
Subject(s) - materials science , band gap , open circuit voltage , photovoltaic system , electron acceptor , energy conversion efficiency , optoelectronics , copolymer , acceptor , polymer , short circuit , organic solar cell , polymer solar cell , fullerene , voltage , photochemistry , organic chemistry , electrical engineering , chemistry , condensed matter physics , physics , composite material , engineering
Alternating copolymers based on cyclopentadithiophene (CPDT) and five different electron‐deficient aromatic units with reduced optical band gaps are synthesized via Suzuki coupling. All polymers show a significant photovoltaic response when mixed with a fullerene acceptor. The frontier orbital levels of the new polymers are designed to minimize energy losses by increasing the open‐circuit voltage with respect to the optical band gap, while maintaining a high coverage of the absorption with the solar spectrum. The best cells are obtained for a copolymer of CPDT and benzooxadiazole (BO) with a band gap of 1.47 eV. This cell gives a short‐circuit current of 5.4 mA cm −2 , an open‐circuit voltage of 0.78 V, and a fill factor of 0.6, resulting in a power conversion efficiency of about 2.5%.