A Nonchlorinated Solvent-Processable Fluorinated Planar Conjugated Polymer for Flexible Field-Effect Transistors

Abstract

High carrier mobilities have recently been achieved in polymer field effect transistors (FETs). However, many of these polymer FET devices require the use of chlorinated solvents such as chloroform (CF), chlorobenzene (CB), and o-dichlorobenzene (DCB) during fabrication. The use of these solvents is highly restricted in industry because of health and environmental issues. Here, we report the synthesis of a low band gap (1.43 eV, 870 nm) semiconducting polymer (PDPP2DT-F2T2) having a planar geometry, which can be readily processable with nonchlorinated solvents such as toluene (TOL), o-xylene (XY), and 1,2,4-trimethylbenzene (TMB). We performed structural characterization of PDPP2DT-F2T2 films prepared from different solvents, and the electrical properties of the films were measured in the context of FETs. The devices exhibited an ambipolar behavior with hole dominant transport. Hole mobilities increased with increasing boiling point (bp) of the nonchlorinated solvents: 0.03, 0.05, and 0.10 cm V s for devices processed using TOL, XY, and TMB, respectively. Thermal annealing further improved the FET performance. TMB-based polymer FETs annealed at 200 °C yielded a maximum hole mobility of 1.28 cm V s, which is far higher than the 0.43 cm V s obtained from the CF-based device. This enhancement was attributed to increased interchain interactions as well as improved long-range interconnection between fibrous domains. Moreover, all of the nonchlorinated solutions generated purely edge-on orientations of the polymer chains, which is highly beneficial for carrier transport in FET devices. Furthermore, we fabricated an array of flexible TMB-processed PDPP2DT-F2T2 FETs on the plastic PEN substrates. These devices demonstrated excellent carrier mobilities and negligible degradation after 300 bending cycles. Overall, we demonstrated that the organized assembly of polymer chains can be achieved by slow drying using high bp nonchlorinated solvents and a post thermal treatment. Furthermore, we showed that polymer FETs processed using high bp nonhalogenated solvents may outperform those processed using halogenated solvents.

Regio-regular alternating diketopyrrolopyrrole-based D1–A–D2–A terpolymers for the enhanced performance of polymer solar cells

“…The onsets of oxidation potential for PDPP2DT-F2T2, PDPPF2T2DPP-T2, PDPPF2T2DPP-TVT, and PDPPF2T2DPP-DTT were 0.49, 0.30, 0.28, and 0.33 V, corresponding to À5.38, À5.10, À5.08, and À5.13 eV of HOMO energy levels, respectively. Fluorine atoms in the PDPP2DT-F2T2 effectively lowered the HOMO level of the PDPP2DT-T2 polymer that has the same chemical structure except uorine atoms, 25 whereas electron-donating units (T2, TVT, and DTT moieties) slightly increased the HOMO levels compare to that of Scheme 1 Synthetic routes for the DPP-based regio-regular terpolymers. the PDPP2DT-F2T2 polymer.…”

“…A comparison with PDPP2DT-T2 synthesized using DPP and 2,2 0 -bithiophene (T2) units revealed that the F2T2 donor moiety could facilitate a planar polymer backbone conformation and enhance crystallinity and carrier transport. 25 In this study, we synthesized three D 1 -A-D 2 -A-type DPPbased terpolymers, in which the D 1 unit was xed with the F2T2 donor, and D 2 units were varied using T2, (E)-1,2di(thiophen-2-yl)ethene (TVT), and dithieno[3,2-b:2 0 ,3 0 -d]thiophene (DTT). The variation of the second donor moiety enabled the ne-tuning of electronic structures, backbone conformation, and the resulting photovoltaic performance.…”

Diketopyrrolopyrrole-based conjugated polymers synthesized by direct arylation polycondensation for anisole-processed high mobility organic thin-film transistors

“…24–26 In the above context, some DPP-based high mobility CPs processible with non-halogenated solvents, such as toluene, xylene, tetralin and tetrahydrofuran (THF), were also reported. 27–38 Lowering the regularity is generally adopted as an effective method to enhance the solubility of CPs. 27–29,39 For instance, Li et al reported toluene-processed DPP-based high mobility CPs with decreased regioregularity.…”

Efficient and Air‐Stable Aqueous‐Processed Organic Solar Cells and Transistors: Impact of Water Addition on Processability and Thin‐Film Morphologies of Electroactive Materials

“…To this end, a great deal of research efforts have been devoted to phasing out halogenated solvents such as chloroform and chlorobenzene, which have been prevalent for optimizing the fabrication of lab‐scale OFET and PSC devices, because they are detrimental to both human health and the environment. In this context, a wide range of halogen‐free solvents including toluene, xylenes, and trimethylbenzenes have been recently proposed as greener solvent alternatives and some notable progress has been made . However, it remains in question whether those halogen‐free solvents, which are often claimed to be “green solvents,” are indeed practically applicable at an industrial‐scale for sustainable manufacturing of organic electronics due to the serious health hazards and harmful environmental impacts that they can pose (e.g., median lethal dose LD 50 for chlorobenzene: 1110 mg kg −1 , toluene: 5580 mg kg −1 , water: >90 000 mg kg −1 , and De minimis % limit allowed to release for chlorobenzene and toluene: 1.0%) .…”