Controlling Conformations of Diketopyrrolopyrrole-Based Conjugated Polymers: Role of Torsional Angle

Transport of charge carriers through conjugated polymers is strongly influenced by the presence and distribution of structural disorders. In the present work, structural defects caused by the presence of torsional angle were investigated in a diketopyrrolopyrrole (<b>DPP</b>)-based conjugated polymer. Two new copolymers of <b>DPP</b> were synthesized with varying torsional angles to trace the role of structural disorder. The optical properties of these copolymers in solution and thin film reveal the strong influence of torsional angle on their photophysical properties. A strong influence was observed on carrier transport properties of polymers in organic field-effect transistors (OFET) device geometry. The polymers based on phenyl DPP with higher torsional angle (<b>PPTDPP</b>-OD-TEG) resulted in high threshold voltage with less charge carrier mobility as compared to the polymer based on thiophene DPP (<b>2DPP</b>-OD-TEG) bearing a lower torsional angle. Carrier mobility and the molecular orientation of the conjugated polymers were correlated on the basis of grazing incidence X-ray scattering measurements showing the strong role of torsional angle introduced in the form of structural disorder. The results presented in this Article provide a deep insight into the sensitivity of structural disorder and its impact on the device performance of DPP-based conjugated polymers

Benzocarborano[2,1‑<i>b</i>:3,4‑<i>b</i>′]dithiophene Containing Conjugated Polymers: Synthesis, Characterization, and Optoelectronic Properties

We report the stannylation of a benzocarborano­[2,1-<i>b</i>:3,4-<i>b</i>′]­dithiophene monomer and its polymerization by Stille polycondensation with solubilized cyclopentadithiophene and diketopyrrolopyrrole derivatives. The physical, material, and optoelectronic properties of the resultant conjugated copolymers are reported, demonstrating that benzocarboranodithiophene acts as a mildly electron-withdrawing monomer

New Fused Bis-Thienobenzothienothiophene Copolymers and Their Use in Organic Solar Cells and Transistors

A new tetradodecyl-substituted DTBTBT donor unit is synthesized by a specific bis-annulation via Suzuki–Miyaura coupling and successfully incorporated into light absorbing electron donor copolymers for OPV and hole and electron transport OFET polymer devices. All copolymers (DTBTBT-<i>co</i>-benzothiadiazole (Bz), DTBTBT-<i>co</i>-thiophene (T) and DTBTBT-<i>co</i>-thienothiophene (TT)) show fully coplanar backbones and strong intermolecular interactions. The DTBTBT-Bz copolymer led to a deep HOMO level (−5.2 eV) and thus a large <i>V</i>_oc value of 0.92 V with PC₇₁BM as electron acceptor and a PCE of 3.7% with a <i>J</i>_sc of 6.78 mA/cm² could be obtained. A hole mobility of 0.1 cm²/(V s) has been observed for the highly coplanar and more crystalline DTBTBT-T copolymer

Fused Dithienogermolodithiophene Low Band Gap Polymers for High-Performance Organic Solar Cells without Processing Additives

We report the synthesis of a novel ladder-type fused ring donor, dithienogermolodithiophene, in which two thieno­[3,2-<i>b</i>]­thiophene units are held coplanar by a bridging dialkyl germanium. Polymerization of this extended monomer with <i>N</i>-octylthienopyrrolodione by Stille polycondensation afforded a polymer, <b>pDTTG-TPD</b>, with an optical band gap of 1.75 eV combined with a high ionization potential. Bulk heterojunction solar cells based upon <b>pDTTG-TPD</b>:PC₇₁BM blends afforded efficiencies up to 7.2% without the need for thermal annealing or processing additives