Efficient doping of polymer semiconductors is required for high conductivity and efficient thermoelectric performance. Lewis acids, e.g., B(C6F5)3, have been widely employed as dopants, but the mechanism is not fully understood. 1:1 “Wheland type” or zwitterionic complexes of B(C6F5)3are created with small conjugated molecules 3,6‐bis(5‐(7‐(5‐methylthiophen‐2‐yl)‐2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)thiophen‐2‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(EDOT)2] and 3,6‐bis(5''‐methyl‐[2,2':5',2''‐terthiophen]‐5‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(Th)2]. Using a wide variety of experimental and computational approaches, the doping ability of these Wheland Complexes with B(C6F5)3are characterized for five novel diketopyrrolopyrrole‐ethylenedioxythiophene (DPP‐EDOT)‐based conjugated polymers. The electrical properties are a strong function of the specific conjugated molecule constituting the adduct, rather than acidic protons generated via hydrolysis of B(C6F5)3, serving as the oxidant. It is highly probable that certain repeat units/segments form adduct structures in
The use of direct CH arylation cross‐coupling polymerization was evaluated for the synthesis of donor–acceptor conjugated co‐polymers using the novel donor 1,6‐didecylnaphtho[1,2‐
- NSF-PAR ID:
- 10458644
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science
- Volume:
- 58
- Issue:
- 9
- ISSN:
- 2642-4150
- Page Range / eLocation ID:
- p. 1299-1310
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract p ‐type conjugated polymers which act as intermediates for conjugated polymer doping. Electronic and optical properties are consistent with the increase in hole‐donating ability of polymers with their cumulative donor strengths. The doped film of polymer (DPP(EDOT)2‐(EDOT)2) exhibits exceptionally good thermal and air‐storage stability. The highest conductivities, ≈300 and ≈200 S cm−1, are achieved for DPP(EDOT)2‐(EDOT)2doped with B(C6F5)3and its Wheland complexes. -
more » « less
Abstract A detailed investigation addressing the effects of functionalizing conjugated polymers with oligo(ethylene glycol) (EG
n ) sidechains on the performance and polymer‐electrolyte compatibility of electrochromic devices (ECDs) is reported. The electrochemistry for a series of donor‐acceptor copolymers having near‐infrared (NIR)‐optical absorption, where the donor fragment is 3,4‐ethylenedioxythiophene (EDOT) or an EGn functionalized bithiophene (g2T) and the acceptor fragment is diketopyrrolopyrrole (DPP) functionalized with branched alkyl or EGn sidechains, is extensively probed. ECDs are next fabricated and it is found that EGn sidechain incorporation must be finely balanced to promote polymer‐electrolyte compatibility and provide efficient ion exchange. Proper electrolyte‐cation pairing and polymer structural tuning affords a 2x increase in optical contrast (from 12% to 24%) and >60x reduction in switching time (from 20 to 0.3 s). Atomic force microscopy (AFM)/grazing incidence wide‐angle X‐ray scattering (GIWAXS) characterization of the polymer film morphology/microstructure reveals that an over‐abundance of EGn sidechains generates large polymer crystallites, which can suppress ion exchange. Lastly, time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) indicates sidechain/electrolyte identity does not influence the electrolyte penetration depth into the films, and EGn sidechain inclusion increases electrolyte cation uptake. The material structural design insight and guidelines regarding the polymer‐electrolyte ion insertion/expulsion dynamics reported here should be of significant utility for developing next‐generation mixed ionic‐electronic conducting materials. -
more » « less
Abstract Donor‐acceptor (D−A) frameworks have been produced via the copolymerization of the strong donor dithieno[3,2‐
b :2′,3′‐d ]pyrrole (DTP) with ambipolar thieno[3,4‐b ]pyrazine (TP) units to generate soluble, processible materials with band gaps as low as 0.8 eV. Optical and electronic characterization of the DTP‐TP copolymers illustrate common misconceptions in the relative contributions of the comonomers to the D‐A framework, as well as highlighting the challenges of minimizing band gap while also retaining desirable frontier orbital energies for application to technological devices. -
more » « less
Abstract Organic semiconducting donor–acceptor polymers are promising candidates for stretchable electronics owing to their mechanical compliance. However, the effect of the electron‐donating thiophene group on the thermomechanical properties of conjugated polymers has not been carefully studied. Here, thin‐film mechanical properties are investigated for diketopyrrolopyrrole (DPP)‐based conjugated polymers with varying numbers of isolated thiophene moieties and sizes of fused thiophene rings in the polymer backbone. Interestingly, it is found that these thiophene units act as an antiplasticizer, where more isolated thiophene rings or bigger fused rings result in an increased glass transition temperature (
T g) of the polymer backbone, and consequently elastic modulus of the respective DPP polymers. Detailed morphological studies suggests that all samples show similar semicrystalline morphology. This antiplasticization effect also exists inpara ‐azaquinodimethane‐based conjugated polymers, indicating that this can be a general trend for various conjugated polymer systems. Using the knowledge gained above, a new DPP‐based polymer with increased alkyl side chain density through attaching alky chains to the thiophene unit is engineered. The new DPP polymer demonstrates a record lowT g, and 50% lower elastic modulus than a reference polymer without side‐chain decorated on the thiophene unit. This work provides a general design rule for making low‐T gconjugated polymers for stretchable electronics. -
more » « less
Abstract We have designed and synthesized a series of deep‐blue light‐emitting polyfluorenes, PF‐27SOs and PF‐36SOs, by introducing electron‐deficient 9,9‐dimethyl‐9
H ‐thioxanthene 10,10‐dioxide isomers (27SO and 36SO) into the poly(9,9‐dioctylfluorene) (PFO) backbone. Compared with PFO, the resulting polymers exhibit an equivalent thermal decomposition temperature (>415 °C), an enhanced glass transition temperature (>99 °C), a decreased lowest unoccupied molecular orbital energy level (E LUMO) below −2.32 eV, a blue‐shifted photoluminescence spectra in solid film with a maximum emission at ~422 nm, and a shoulder peak at ~445 nm. The resulting polymers also show blue‐shifted and narrowed electroluminescence spectra with deep‐blue Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.07) for PF‐27SO20 and (0.16, 0.06) for PF‐36SO30, compared with (0.17, 0.13) for PFO. Moreover, simple device based on PF‐36SO30 achieves a superior device performance with a maximum external quantum efficiency (EQEmax= 3.62%) compared with PFO (EQEmax= 0.47%). The results show that nonconjugated 9,9‐dimethyl‐9H ‐thioxanthene 10,10‐dioxide isomers can effectively perturb the conjugation length of polymers, significantly weaken the charge‐transfer effect in donor–acceptor systems, substantially improve electroluminescence device efficiency, and achieve deep‐blue light emission.
