Alkoxy‐Functionalized Thienyl‐Vinylene Polymers for Field‐Effect Transistors and All‐Polymer Solar Cells

Abstract

π-conjugated polymers based on the electron-neutral alkoxy-functionalized thienyl-vinylene (TVTOEt) building-block co-polymerized, with either BDT (benzodithiophene) or T2 (dithiophene) donor blocks, or NDI (naphthalenediimide) as an acceptor block, are synthesized and characterized. The effect of BDT and NDI substituents (alkyl vs alkoxy or linear vs branched) on the polymer performance in organic thin fi lm transistors (OTFTs) and all-polymer organic photovoltaic (OPV) cells is reported. Comonomer selection and backbone functionalization substantially modifi es the polymer MO energies, thin fi lm morphology, and charge transport properties, as indicated by electrochemistry, optical spectroscopy, X-ray diffraction, AFM, DFT calculations, and TFT response. When polymer P7 is used as an OPV acceptor with PTB7 as a donor, the corresponding blend yields TFTs with ambipolar mobilities of µ e = 5.1 × 10 −3 cm 2 V -1 s -1 and µ h = 3.9 × 10 −3 cm 2 V -1 s -1 in ambient, among the highest mobilities reported to date for all-polymer bulk heterojunction TFTs, and all-polymer solar cells with a power conversion effi ciency (PCE) of 1.70%, the highest reported PCE to date for an NDI-polymer acceptor system. The stable transport characteristics in ambient and promising solar cell performance make NDI-type materials promising acceptors for all-polymer solar cell applications.

Achieving high performance non-fullerene organic solar cells through tuning the numbers of electron deficient building blocks of molecular acceptors

“…Note the high and balanced charge transport capability is critical to efficiently collect the charges after splitting the excitons [68], which is consistent with the much higher J SC for PTB7-Th:SF-PDI4 based solar cells. Similarly, the hole mobility of PffBT4T-2OD:SF-PDI2 is 2.17 Â 10 À4 cm 2 /V$s, around ten times higher than the electron mobility of 2.20 Â 10 À5 cm 2 /V$s.…”

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

“…Figure 6 shows the conventional device architecture of BHJ OPVs. The formation of interpenetrating networks requires the phase separation of component materials, in which the interfacial energy favors a large surface area and that each of the two components is fully percolated with connected pathways to the electrodes [76][77][78]. An "ordered bulk heterojunction", consisting of vertically aligned conjugated polymer nanorods surrounded by the electron acceptor materials to form the ordered bicontinuous heterojunction morphology for the active layer, yet achieving this morphology, has been elusive [79,80].…”

Role of Solution Structure in Self-Assembly of Conjugated Block Copolymer Thin Films

“…55 In these CBCP OPVs, the phase separation at ~16 nm scale of blocks of P3HT and a fluorene-benzodiathiazolebased co-polymer (PFTBT) led to solar cells with high open circuit voltage and external quantum efficiencies of ~30%. These PCEs, however, lag those of physical blends of polymers, 22,22,[56][57][58] which have now reached ~7.7% using an acceptor based on a naphthalene diimide-selenophene copolymer acceptor and a donor based on a benzodithiophene-thieno [3,4-b]thiophene copolymer. 21 There are critical questions whether the differences in efficiency are simply due to materials choice, i.e.…”