Wei Lin Leong

Organic electrochemical transistors (OECTs) have evolved from passive electrodes into active transducers that sense, amplify, and increasingly compute at the boundary between circuits and living tissue. Over the past decade, advances span molecular design of organic mixed ionic–electronic conductors (OMIECs), electrolyte and channel engineering, device architectures, and circuit integration, to system‐level translation. Unlike existing reviews that treat these in isolation, emphasizing single material classes, mechanisms, or applications, this article unifies them through bioelectronic interface design, working from biological demands to demonstrated capabilities. We analyze operating principles, benchmarking metrics and structure–property relationships across p‐type, n‐type, and biodegradable OMIECs. The electrolyte‐channel region emerges as where biology and electronics converge; we survey gel electrolytes, semiconducting hydrogels, and all‐gel devices, alongside planar, vertical, fiber, textile, and printed architectures. We assess how design choices impact performance across electrophysiological, biochemical, implantable, wearable, and plant‐bioelectronic applications, while addressing biocompatibility, stability, and standardization requirements. Finally, we outline OECT‐native platforms that consolidate sensing, memory, computation, and actuation within closed‐loop, autonomous bioelectronic interfaces, arguing that this convergence represents the most consequential near‐term direction for the field.

The integration of optical sensing, signal amplification, memory, and computation in compact devices is important for artificial visual systems, neuromorphic electronics, and robotics. Organic photoelectrochemical transistors (OPECTs) offer a promising platform, as their photonic–ionic–electronic coupling enables low‐voltage operation and intrinsic amplification. However, most single‐component OPECTs rely on n ‐type mixed ionic–electronic conductors, while high‐performing p ‐type devices remain scarce. Advancing p ‐type photoactive materials is crucial for complementary circuits with reconfigurable responses. We report a high‐performance p ‐type OPECT based on the ladder‐type organic conductor, PBBT‐Me, serving as both light‐sensitive channel and gate electrode. Under illumination, the device achieves a photocurrent of ∼640 µA, and a photoinduced transconductance modulation ratio of 35, combining strong photoresponse with transistor amplification. The effect arises from light‐induced gate potential modulation that enhances electrochemical channel doping and increases drain current. Beyond photodetection, the OPECT emulates optical synaptic functions such as short‐term plasticity, paired‐pulse facilitation, and rehearsal learning, enabling neuromorphic preprocessing for digit recognition. A complementary, light‐controlled inverter operates as a voltage‐to‐voltage photoamplifier with gain of 120 V/V, supporting optically switchable OR/NOR logic. Integration with robotic platforms further demonstrates light‐controlled gestures and motion, establishing p ‐type ladder‐polymer OPECTs as versatile building blocks for compact optoelectronic and neuromorphic systems.

Printable carbon-based perovskite solar cells (C-PSCs) offer a low-cost and durable photovoltaic platform but remain limited by poor interfacial charge extraction and substantial nonradiative recombination at the perovskite/carbon junction suppressing open-circuit voltage (VOC). While phosphonic acid–based self-assembled monolayers (SAMs) are widely used in p–i–n devices, their application in mesoscopic carbon architectures remains unexplored. Here, we report a simple post-treatment based on the molecular self-assembled monolayer MeO-2PACz to address these bottlenecks in triple-mesoscopic TiO2/ZrO2/carbon architectures. MeO-2PACz treatment modulates the perovskite/carbon interface, improving energy-level alignment and passivating undercoordinated Pb2+ sites. Transient photocurrent and transient photovoltage analyses show accelerated charge extraction and extended recombination lifetimes. Consequently, the SAM-treated devices achieve enhanced VOC (0.90 V), fill factor (70.7%), and a champion power conversion efficiency (PCE) of 14.7%, along with suppressed hysteresis and improved stability, retaining 98% of initial PCE after 2400 h under controlled humidity without encapsulation.

Printed organic electrochemical transistors (OECTs) are promising for next‐generation biosensing and neuromorphic computing, owing to their high transconductance, low operating voltage, mechanical flexibility, and efficient volumetric ionic–electronic coupling. Yet, printable n ‐type OECTs have lagged their p ‐type counterparts due to limited stability and poor printability. The key challenge lies in achieving high electronic conductivity, efficient ionic accessibility, and rheological properties compatible with scalable printing. To address this, we developed a screen‐printable, air‐stable, n ‐type OECT channel by blending high‐conductivity poly(benzodifurandione) (PBFDO) with poly(ethylene oxide) (PEO). Devices fabricated using 5wt.% PEO blend and a gelatin‐based electrolyte exhibited tunable transient responses (turn‐on time; 9.6 to 419 ms, turn‐off time; 4.3 ms to 17.8 ms), stable operation (92.4% ON current retained over 1,000 cycles), and high uniformity across 50 devices (I _{ds, ON} = 2.47 ± 0.29 mA and transconductance g _m = 3.55 ± 0.57 mS). PEO transforms low‐viscosity PBFDO solutions into shear‐thinning pastes suitable for screen printing, while enhancing film wettability and electrolyte infiltration. This dual role promotes efficient ion penetration and improves printability, enabling devices with improved transient speeds and rheological properties optimized for scalable fabrication. By controlling channel thickness, thin devices enable electrocardiogram signal acquisition while thick devices act as artificial synapses, highlighting PBFDO‐based inks as versatile platforms for integrated bioelectronic interfaces.

Carbazole-derived hole-selective self-assembled monolayer (SAM) contacts are indispensable for high-performance inverted perovskite solar cells. Nevertheless, self-aggregation and molecular desorption of SAM result in a fragile heterogeneous interface, severely hindering device reproducibility and stability. Here, we propose a proton transfer complex-confined strategy to address the interfacial spatial heterogeneity, thereby enhancing the dispersion and adsorption of SAMs. This achieves a multi-site coupling design at the buried interface, effectively preventing interface destabilization by thermal stress. Consequently, a champion efficiency of 26.23% is achieved, with an impressive fill factor (85.64%). These devices resist thermal degradation at 75 °C for 1368 h. Notably, the potential difference change of the target SAMs after thermal degradation at 150 °C is only 5.9 mV, confirming its interfacial chemical stability. The corresponding perovskite film withstands 100 thermal stress cycles (–60 °C ∼ 85 °C). This strategy also achieves higher photovoltaic performance at a lower temperature (240 K).

The human integumentary system encodes external stimuli into temporally and spatially patterned spike signals for transmission to the central nervous system. Inspired by this biological process, we present a symmetric cross‐coupled organic neuron based on accumulative n‐type organic electrochemical transistors (OECTs). By utilizing only two identical n‐type accumulation‐mode OECTs, our system reproduces ten distinct biologically relevant spiking behaviors and operates robustly across diverse semiconductors and electrolytes, establishing a material‐general framework for OECT‐based neurons. Its spiking dynamics can be modulated by ionic, optical, and mechanical stimuli. Coupling the low‐power neuron with a photodetector further enables light‐driven, energy‐autonomous operation. The system also enables multimodal sensory integration and selective signal decoupling via frequency‐division multiplexing, offering a potential route toward complex sensory processing. Separately, the system achieves functional biological integration by interfacing with Venus flytraps to control leaf closure via artificial spikes. These results establish our materials‐versatile strategy as a versatile framework for constructing organic artificial neuromorphic systems, providing a new pathway toward next‐generation material‐independent neuromorphic architectures, multimodal sensory integration, and bio‐interfacing technologies.

Electronic skin for robotics often suffers from limited scalability, high fabrication costs, and inflexible designs, restricting its ability to support multimodal sensing and customization. To address these challenges, we propose a robotic e-skin fabricated using direct-ink-writing technology that enables rapid customization and scalable production of multimodal sensors. The e-skin can detect pressure, temperature, and shear forces through a facile sensor design modification without additional complex fabrication steps. The pyramid-structured tactile sensor demonstrates high sensitivity of 670 kPa^-1 in the 0-100 kPa range, maintain long-term stability over 3500 cycles, and exhibits minimal signal drift of less than 3% after 9 days of continuous testing. A 4 × 9 flexible sensor array is developed for real-time pressure mapping on both flat and curved surfaces. Integration with a robotic gripper combined with a K-nearest neighbor classifier achieves a 97.7% accuracy in object recognition. Furthermore, by replacing the sensing layer with a temperature-responsive polymer or incorporating a protrusion-patterned shear layer, the e-skin can function as a dual-mode temperature-pressure sensor or a shear-force sensor. This highly versatile and scalable e-skin platform opens new possibilities for applications in robotics, prosthetics, and human-machine interfaces.