Intramolecular donor–acceptor structures prepared by covalently binding conjugated octylphenanthrenyl‐imidazole moieties onto the side chains of regioregular poly(3‐hexylthiophene)s exhibit lowered bandgaps and enhanced electron transfer compared to the parent polymer, e.g., conjugation of 90 mol% octylphenanthrenyl‐imidazole moieties onto poly(3‐hexylthiophene) chains reduces the optical bandgap from 1.91 to 1.80 eV, and the electron transfer probability is at least twice as high as that of pure poly(3‐hexylthiophene) when blended with [6,6]‐phenyl‐C61‐butyric acid methyl ester. The lowered bandgap and the fast charge transfer both contribute to much higher external quantum efficiencies, thus much higher short‐circuit current densities for copolymers presenting octylphenanthrenyl‐imidazole moieties, relative to those of pure poly(3‐hexylthiophene)s. The short‐circuit current density of a device prepared from a copolymer presenting 90 mol% octylphenanthrenyl‐imidazole moieties is 13.7 mA · cm−2 which is an increase of 65% compared to the 8.3 mA · cm−2 observable for a device containing pure poly(3‐hexylthiophene). The maximum power conversion efficiency of this particular copolymer is 3.45% which suggest that such copolymers are promising polymeric photovoltaic materials.

A pentacyclic indacenodiselenophene (IDS) arene was synthesized via intramolecular Friedel-Craft cyclization of the selenophene moieties. This IDS framework was used as a model system to investigate the alkyl/alkoxy side-chain effect by preparing IDS-OCH 8 and IDS-C 6 , where the side chains on the sp 3 carbon in the cyclopentadienyl ring are 4octyloxyphenyl groups and 4-hexylphenyl groups, respectively. The Sn-IDS-OCH 8 and Sn-IDS-C 6 monomers were copolymerized with 4,7dibromo-2,1,3-benzothiadiazole (BT), 4,7-diiodo-5,6-difluoro-2,1,3-benzothiadiazole (FBT) and 1,3-dibromothieno[3,4-c]pyrrole-4,6-dione (TPD) acceptor monomers by Stille polycondensation to afford five new IDSbased donor−acceptor alternating copolymers, PIDSBT-OCH 8 , PIDSBT-C 6 , PIDSFBT-OCH 8 , PIDSFBT-C 6 , and PIDSTPD-C 6 . Despite the fact that the octyloxy and hexyl side chains play a negligible role in the optical and electrochemical properties of the resulting polymers, the solar cell performance is highly associated with the side chains of the polymers. Under similar device fabrication conditions, the PIDSBT-C 6 and PIDSFBT-C 6 -based devices showed much improved efficiencies than the corresponding PIDSBT-OCH 8 , and PIDSFBT-OCH 8 -based devices (2.6% and 1.9% vs 3.8% and 3.9%). The improvement is mainly the result of much enhanced J sc values. Consistently, PIDSBT-C 6 and PIDSFBT-C 6 exhibited much higher FET hole mobilites than the corresponding PIDSBT-OCH 8 , and PIDSFBT-OCH 8 . These results clearly revealed that the 4-hexylphenyl group is a more suitable side chain than the 4-octyloxyphenyl group in the IDS system, and the side-chain dependent mobility of the polymers is the dominating factor to determine the photocurrents and efficiencies of PSCs. PIDSBT-C 6 exhibited a high hole mobility of 0.08 cm 2 V −1 s −1 and PIDSTPD-C 6 :PC 71 BM (1:4 in wt %)-based solar cell with 5 v% chloronaphthalene (CN) delivered a V oc of 0.92 V, a J sc of 9.77 mA/cm 2 , an FF of 51%, and a highest PCE of 4.6%. This work not only discloses a new selenophene-containing ladder-type IDS structure and its copolymers but also provides useful insights into the alkyl/alkoxy side-chain effect for future design of conjugated polymers.

2,2′‐dipyridylamine substituted poly(fluorene‐co‐phenylene) copolymers with different concentrations of dipyridylamine have been synthesized by Suzuki polycondensation. These polymers were found to be soluble in organic solvents such as tetrahydrofuran, chloroform, and dimethylformamide. The photoluminescence of the copolymer was slightly blueshifted as the concentration of dipridylamine was increased. The introduction of dipyridylamine and the ruthenium complex into the polymer significantly improved the photoluminescence efficiency. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4838–4846, 2004

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