Although high-temperature operation (i.e., beyond 150°C) is of great interest for many electronics applications, achieving stable carrier mobilities for organic semiconductors at elevated temperatures is fundamentally challenging. We report a general strategy to make thermally stable high-temperature semiconducting polymer blends, composed of interpenetrating semicrystalline conjugated polymers and high glass-transition temperature insulating matrices. When properly engineered, such polymer blends display a temperature-insensitive charge transport behavior with hole mobility exceeding 2.0 cm2/V·s across a wide temperature range from room temperature up to 220°C in thin-film transistors.

We describe the 3-iodopropyl acetal moiety as a simple cleavable unit that undergoes acid catalyzed hydrolysis to liberate HI (pK a ∼ −10) and acrolein stoichiometrically. Integrating this unit into linear and network polymers gives a class of macromolecules that undergo a new mechanism of degradation with an acid amplified, sigmoidal rate. This trigger-responsive self-amplified degradable polymer undergoes accelerated rate of degradation and agent release.

All-plastic transistor devices with thermal stability up to 220 °C are demonstrated. We employ polyimide substrates, polyimide dielectrics, and a polyimide-based semiconducting blend to achieve flexible and thermally-robust transistors. An in situ temperature-dependent charge transport study was used to demonstrate that these devices can operate in extremely high temperatures and can sustain prolonged baking. Our devices maintained stable charge-transport characteristics with charge mobilities of 0.20 cm2/(V s), I ON/I OFF of 104, threshold voltage of 3 V, and operational voltage of 10 V when baked at 195 °C for 2 h.

The limited availability of solution-processable ion storage materials, both inorganic and organic, hinders the adoption of roll-to-roll manufacturing for polymer electrochromic devices (ECDs). The n-type transition metal oxides are known for their ion storage properties. However, the fabrication methods of their amorphous metal oxide thin films typically involve sputtering, thermal deposition, electrical deposition, or sol−gel deposition followed by high-temperature thermal annealing (>300 °C), thus making them incompatible for low-cost roll-to-roll manufacturing on flexible substrates. In this study, we report the synthesis of amorphous niobium oxide(a-Nb 2 O 5 ) thin films from sol−gel precursors through the combination of photoactivation and low-temperature thermal annealing (150 °C). Coupled with p-type electrochromic polymers (ECPs), solution-processed a-Nb 2 O 5 thin films were evaluated as a minimally color changing counter electrode (MCC-CE) material for electrochromic devices. We found that ultraviolet ozone (UVO) treated and 150 °C thermally annealed (UVO-150 °C) a-Nb 2 O 5 thin films show excellent electrochemical properties and cycling stability. Notably, a-Nb 2 O 5 /ECP-magenta ECD has a high optical contrast of ∼70% and a fast switching time (bleaching and coloring time of 1.6 and 0.5 s for reaching 95% of optical contrast). In addition, the ECD demonstrates a high coloration efficiency of ∼849.5 mC cm −2 and a long cycling stability without a noticeable decay up to 3000 cycles.

Organic electrochemical transistors (OECTs) are oft-used for bioelectronic applications, and a variety of OECT channel materials have been developed in recent years. However, the majority of these materials are still limited by long-term performance and stability challenges. To resolve these issues, we implemented a next-generation design of polymers for OECTs. Specifically, diketopyrrolopyrrole (DPP) building blocks were copolymerized with propylene dioxythiophene-based (Pro-based) monomers to create a donor−acceptor-type conjugated polymer (PProDOT-DPP). These PProDOT-DPP macromolecules were synthesized using a straightforward direct arylation polymerization synthetic route. The PProDOT-DPP polymer thin film exhibited excellent electrochemical response, low oxidation potential, and high crystallinity, as evidenced by spectroelectrochemical measurements and grazing incidence wide-angle X-ray scattering measurements. Thus, the resultant polymer thin films had high charge mobility and volumetric capacitance values (i.e., μC* as high as 310 F cm −1 V −1 s −1 ) when they were used as the active layer materials in OECT devices, which places PProDOT-DPP among the highest performing accumulation-mode OECT polymers reported to date. The performance of the PProDOT-DPP thin films was also retained for 100 cycles and over 2000 s of ON−OFF cycling, indicating the robust stability of the materials. Therefore, this effort provides a clear roadmap for the design of electrochemically active macromolecules for accumulation-mode OECTs, where crystalline acceptor cores are incorporated into an all-donor polymer. We anticipate that this will ultimately inspire future polymer designs to enable OECTs with both high electrical performance and operational stability.

Understanding high-temperature operation in organic semiconductors remains elusive. Here, we studied the effect of two alkyl side-chains, 2-octyldodecyl (C1) and 4-decyltetracecyl (C3), on the thermal stability of two types of conjugated polymer backbones: isoindigo (IID) and diketopyrolopyrrole (DPP). All polymers remain functional with high on/off ratio in ambient air at temperature up to 220 °C. However, the use of longer side-chain C3 lowers the π–π stacking distance and enables more thermally stable polymer thin film field-effect-transistors. Specifically, IID-C3 and DPP-C3 exhibited less alteration in threshold voltage as well as a reduction in effective mobility at high temperature. This behavior emphasizes the importance of close π–π stacking distance on charge transport properties of conjugated polymers and their thermal stability. This study is a starting point to deconvolute the intricate mechanism of charge transport in polymer thin films at elevated temperatures.

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Side-chain sequence enabled regioisomeric acceptors, bearing different side-chain sequences on the same conjugated backbone, are herein reported. Two regioregular polymers PTBI-1 and PTBI-2 and one regiorandom polymer PTBI-3 were synthesized from these two regioisomeric acceptors for a comparative study. UV–vis–NIR absorption spectroscopy and electrochemical study confirmed similar frontier molecular orbital levels of the three polymers in their solid state. More intriguingly, absorption profiles suggest that the sequence of side chains greatly governs the aggregation behaviors. Furthermore, the PTBI-2 film shows larger ordered domains than PTBI-1 and PTBI-3 films, as supported by AFM and GIWAXS measurements. As a result, PTBI-2-based FET devices achieved an average hole mobility of 1.37 cm2 V–1 s–1, much higher than the two polymers with other side-chain sequences. The regiorandom PTBI-3 exhibited the lowest average hole mobility of 0.27 cm2 V–1 s–1. This study highlights the significant impact of side-chain sequence regioisomerism on aggregation behaviors, morphologies, and subsequently charge transport properties of donor–acceptor type conjugated polymers.