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Synthesis and photovoltaic device studies of azo‐linked low‐bandgap polymers
Author(s) -
Meena Savita,
Alam Firoz,
Dutta Viresh,
Jacob Josemon
Publication year - 2017
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.5299
Subject(s) - monomer , polymer chemistry , copolymer , polymerization , polymer , materials science , halogenation , chemistry , organic chemistry
We report the synthesis of a series of new polymers containing azo linkage as a part of the main chain. The monomer 1,2‐bis(7‐bromo‐9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazene was synthesized using a precursor approach which avoids non‐selective bromination and was copolymerized with various donor or acceptor units. The homopolymer poly[1,2‐bis(9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazene] ( P1 ) as well as the copolymers poly[1‐(9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)‐2‐(9,9,9′,9′‐tetraoctyl‐9 H ,9′ H ‐[2,2′‐bifluoren]‐7‐yl)diazene] ( P2 ), poly[1‐(9,9‐dioctyl‐7‐(4‐octylthiophen‐2‐yl)‐9 H ‐fluoren‐2‐yl)‐2‐(9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazene] ( P3 ) and poly[4‐(7‐((9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazenyl)‐9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)benzo[ c ][1,2,5]thiadiazole] ( P4 ) were synthesized by Suzuki polymerization. The copolymers poly[1‐(7‐(4,4‐dioctyl‐4 H ‐cyclopenta[1,2‐ b :5,4‐ b ′]dithiophen‐2‐yl)‐9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)‐2‐(9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazene] ( P5 ) and poly[4‐(5‐(7‐((9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)diazenyl)‐9,9‐dioctyl‐9 H ‐fluoren‐2‐yl)‐4‐octylthiophen‐2‐yl)‐7‐(4‐octylthiophen‐2‐yl)benzo[ c ][1,2,5]thiadiazole] ( P6 ) were synthesized by direct arylation polymerization reaction. Polymers synthesized using the direct arylation method show good molecular weight, with absorption maxima in the range 500 to 532 nm. P5 and P6 possess low optical bandgaps of 1.81 and 1.86 eV, respectively. A power conversion efficiency of 0.53% with open circuit voltage of 0.53 V, short circuit current density of 3.1 mA cm −2 and fill factor of 29% has been achieved with C71‐PCBM as acceptor in bulk heterojunction solar cells fabricated with P5 as donor. © 2016 Society of Chemical Industry