Stretchable electronics have received great attention in recent years because they enable to accommodate large mechanical deformation without damaging electronic properties. These features are highly desirable for novel applications, including...

Brain-inspired synaptic transistors have been considered as a promising device for next-generation electronics. To mimic the behavior of a biological synapse, both data processing and nonvolatile memory capability are simultaneously required for a single electronic device. In this work, a simple approach to realize a synaptic transistor with improved memory characteristics is demonstrated by doping an ionic additive, tetrabutylammonium perchlorate (TBAP), into an active polymer semiconductor without using any extra charge storage layer. TBAP doping is first revealed to improve the memory window of a derived transistor memory device from 19 to 32 V (∼68% enhancement) with an on/off current ratio over 10 3 at V G = −10 V. Through morphological analysis and theoretical calculations, it is revealed that the association of anion with polymers enhances the charge retention capability of the polymer and facilitates the interchain interactions to result in improved memory characteristics. More critically, the doped device is shown to successfully mimic the synaptic behaviors, such as paired-pulse facilitation (PPF), excitatory and inhibitory postsynaptic currents, and spike-rate dependent plasticity. Notably, the TBAP-doped device is shown to deliver a PPF index of up to 204% in contrast to the negligible value of an undoped device. This study describes a novel approach to prepare a synaptic transistor by doping conjugated polymers, which can promote the future development of artificial neuromorphic systems.

We demonstrate a transparent stretchable supercapacitor based on a nanocomposite electrode consisting of silver nanowires (AgNWs) and poly­(3,4-ethylenedioxythiophene)-poly­(styrenesulfonate) (PEDOT:PSS) modified with ethylene glycol. The addition of ethylene glycol (EG) in the PEDOT:PSS solution can dramatically enhance the conductivity of the polymer film. Furthermore, the solvent treatment induces the reorganization of the polymer chains, leading to better distribution of PEDOT:PSS on the AgNW network. With the EG-enhanced AgNWs/PEDOT:PSS electrode, an 87% transmittance of the nanocomposite electrode can be achieved at a wavelength of 550 nm and a pseudo capacitance of 113 ± 18 F/g (areal capacitance = 2.83 ± 0.46 mF cm–2) can be achieved at a scan rate of 10 mV/s. When it was stretched with a tensile strain of 40%, the capacitance of the transparent supercapacitor even increased, owing to closer electrode contact. This work provides a facile way to produce highly transparent and stretchable electrodes using EG-enhanced nanocomposite for a stretchable portable power source of transparent electronics.

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Three-terminal synaptic transistor has drawn significant research interests for neuromorphic computation due to its advantage of facile device integrability. Lately, bulk-heterojunction-based synaptic transistors with bipolar modulation are proposed to exempt the use of an additional floating gate. However, the actual correlation between the channel's ambipolarity, memory characteristic, and synaptic behavior for a floating-gate free transistor has not been investigated yet. Herein, by studying five diketopyrrolopyrrole-benzotriazole dual-acceptor random conjugated polymers, a clear correlation among the hole/electron ratio, the memory retention characteristic, and the synaptic behavior for the polymer channel layer in a floating-gate free transistor is described. It reveals that the polymers with balanced ambipolarity possess better charge trapping capabilities and larger memory windows; however, the high ambipolarity results in higher volatility of the memory characteristics, namely poor memory retention capability. In contrast, the polymer with a reduced ambipolarity possesses an enhanced memory retention capability despite showing a reduced memory window. It is further manifested that this enhanced charge retention capability enables the device to present artificial synaptic characteristics. The results highlight the importance of the channel's ambipolarity of floating-gate free transistors on the resultant volatile memory characteristics and synaptic behaviors.

Stretchable polymer semiconductors are an essential component for skin‐inspired electronics. However, the lack of scalable patterning capability of stretchable polymer semiconductors limits the development of stretchable electronics. To address this issue, photo‐curable stretchable polymer blends consisting of a high‐mobility donor–acceptor conjugated polymer and an elastic rubber through thiol–ene chemistry are developed. The thiol–ene reaction can selectively cross‐link the rubber with alkene or vinyl groups without damaging the electronic properties of the conjugated polymer. The conjugated polymer chains embedded in the elastic polymer matrix induce a semi‐interpenetrating polymer network (SIPN). The thiol–ene‐cross‐linked network provides great solvent resistance and enhances stretchability for the embedded conjugated polymer. The well‐defined patterned film with a feature size of ≈10 µm can be obtained using UV light at 365 nm through conventional photolithography processes. Furthermore, the SIPN‐based transistors show increased mobilities from 0.61 to 1.18 cm2 V−1 s−1 when applying the strain from 0% to 100%. Moreover, the hole mobility can still maintain at 0.87 cm2 V−1 s−1 after 1000 strain‐and‐release cycles at the strain of 25%. This study sheds light on the molecular design of photo‐curable polymer semiconductors for the mass production of stretchable circuits.

Floating-gate Free transistorsIn article number 2203025, Yu-Ting Yang, Wen-Ya Lee, Chu-Chen Chueh, and co-workers reveal a floating-gate-free transistor based on the ambipolar diketopyrrolopyrrole-based conjugated polymers. The correlations between the channel's ambipolarity, memory characteristics, and synaptic behaviors are systematically investigated. The µh/µe mobility ratio is critical for controlling device characteristics from nonvolatile memory to artificial synapses.