1 research outputs found
Highly Efficient and Balanced Charge Transport in Thieno[3,4‑<i>c</i>]pyrrole-4,6-dione Copolymers: Dramatic Influence of Thieno[3,2‑<i>b</i>]thiophene Comonomer on Alignment and Charge Transport
The
design, synthesis, characterization, and application of a novel
series of copolymers based on the electron deficient thienoÂ[3,4-<i>c</i>]Âpyrrole-4,6-dione building block, copolymerized with either
thienoÂ[3,2-<i>b</i>]Âthiophene (PTPDTT) or thiophene (PTPDT),
are reported. High molecular weights were obtained for PTPDTT via
Stille polycondensation. For the PTPDTs, different molecular weights
were achieved by varying the polymerization conditions. The increase
in molecular weight (PTPDT-2) favors face-on alignment and increases
the charge carrier mobility. Grazing-incidence wide-angle X-ray scattering
measurements reveal higher crystallinity for PTPDTT with up to 5 orders
of lamellar stacking compared to PTPDTs. All polymers show ambipolar
charge transport with highly balanced hole and electron mobilities
in organic field effect transistors (OFETs), which improve considerably
upon thermal annealing. A shift of comonomer from simple thiophene
in PTPDT-2 to planar and electron-dense thienothiophene in PTPDTT
drastically changes the alignment from face-on to edge-on fashion.
Consequently, the charge carrier mobility increases considerably by
1 order of magnitude in PTPDTT, reaching excellent charge carrier
mobilities for both holes (0.11 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) and electrons (0.17 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>). PTPDTT was tested as a donor
material in combination with PC<sub>71</sub>BM as well as an acceptor
material along with a donor polymer. As a donor material, a power
conversion efficiency of 4.3% was reached in combination with PC<sub>71</sub>BM