Van der Waals Multilayer Heterojunction for Low-Voltage Organic RGB Area-Emitting Transistor Array

Organic light-emitting transistors with high efficiency and narrow emission originating from intrinsic multiple-order microcavities

Narrow electroluminescence is in high demand for high-resolution displays, optical communication and medical phototherapy. Organic light-emitting transistors, as three-terminal electroluminescent devices, offer advantages in simplifying device architecture and achieving high efficiency under gate regulation. However, achieving high efficiency and narrow emission remains a challenge. Here we demonstrate that laterally integrated organic light-emitting transistors with intrinsic multiple-order microcavities can enhance efficiency and narrow emission with a universal capability for different emitters. Full-width at half-maximum values of 18 nm for red, 14 nm for green and 13 nm for blue were achieved with a maximum narrowed degree of 68%. This resulted in an impressive BT.2020 colour gamut of 97%. The peak current efficiency or blue index values for red, green and blue organic light-emitting transistors reached 26.3 cd A-1, 37.3 cd A-1 and 72.6, respectively. Moreover, organic light-emitting transistors exhibit much narrower emission and higher efficiency than equivalent, comparable devices due to their unique gate regulation capability. Our work could enable smart display technologies with high colour purity and enhanced efficiency.

UV/Ozone-Induced Interface Engineering for High-Performance Horizontal Organic Light-Emitting Transistors Operating at Low Voltage

Multifunctional organic light-emitting transistors (OLETs), which combine electric-switching and light-producing capabilities into a single device, are attracting increasing interest as promising candidates for new-generation display technology. Despite advancements in the design of organic luminescent materials and the optimization of device geometry configurations, maintaining operating voltage low while enhancing optical performances remains a key challenge in horizontally structured OLETs. Here, a simple and effective interfacial engineering strategy is employed to improve the optical properties of horizontal OLETs operating at low voltage, by introducing ultraviolet ozone (UVO)-induced surface modification on high-k dielectrics. It takes the role to not only control the surface activation states of dielectric layers but also optimize the growth dynamics behavior of channel film benefitting from the strong interfacial interaction between chemically modified dielectric surface and channel seed molecules. The optimized horizontal-channel OLET exhibits a significantly high brightness of 9,484 cd m- 2, more than 25 times greater than that of untreated OLETs (347 cd m- 2), along with a peak EQE of 9.64%, a low operating voltage of 15 V, and good dynamic gate stress stability, outperforming other reported horizontal-channel high-performance OLETs. This work demonstrates that dielectric/semiconductor interface engineering is essential for high-performance transistor-based optoelectronic devices including horizontal OLETs.

Li Promoting Long Afterglow Organic Light-Emitting Transistor for Memory Optocoupler Module

The artificial brain is conceived as advanced intelligence technology, capable to emulate in-memory processes occurring in the human brain by integrating synaptic devices. Within this context, improving the functionality of synaptic transistors to increase information processing density in neuromorphic chips is a major challenge in this field. In this article, Li-ion migration promoting long afterglow organic light-emitting transistors, which display exceptional postsynaptic brightness of 7000 cd m-2 under low operational voltages of 10 V is presented. The postsynaptic current of 0.1 mA operating as a built-in threshold switch is implemented as a firing point in these devices. The setting-condition-triggered long afterglow is employed to drive the photoisomerization process of photochromic molecules that mimic neurotransmitter transfer in the human brain for realizing a key memory rule, that is, the transition from long-term memory to permanent memory. The combination of setting-condition-triggered long afterglow with photodiode amplifiers is also processed to emulate the human responding action after the setting-training process. Overall, the successful integration in neuromorphic computing comprising stimulus judgment, photon emission, transition, and encoding,  to emulate the complicated decision tree of the human brain is demonstrated.

High-efficiency crystalline white organic light-emitting diodes

Crystalline white organic light-emitting diodes (C-WOLEDs) are promising candidates for lighting and display applications. It is urgently necessary, however, to develop energy-saving and high-efficiency C-WOLEDs that have stable and powerful emission to meet commercial demands. Here, we report a crystalline host matrix (CHM) with embedded nanoaggregates (NA) structure for developing high-performance C-WOLEDs by employing a thermally activated delayed fluorescence (TADF) material and orange phosphorescent dopants (Phos.-D). The CHM-TADFNA-D WOLED exhibit a remarkable EQE of 12.8%, which is the highest performance WOLEDs based on crystalline materials. The device has a quick formation of excitons and a well-designed energy transfer process, and possesses a fast ramping of luminance and current density. Compared to recently reported high-performance WOLEDs based on amorphous material route, the C-WOLED achieves a low series-resistance Joule-heat loss ratio and an enhanced photon output, demonstrating its significant potential in developing the next-generation WOLEDs.

High-Efficiency Area-Emissive White Organic Light-Emitting Transistor for Full-Color Display

The construction of high-performance white organic light-emitting transistor (OLET) with uniform area emission is crucial for smart display technologies but remains greatly challenging. Herein, high-efficiency uniform area-emissive OLETs based on a unique lateral-integrated device configuration which incorporates efficient energy transfer of phosphorescent and fluorescent guests, enabling color-tunable and white emission, are demonstrated. Through precisely regulating the energy transfer between host and guests, high external quantum efficiency of 13.9% for white-emission OLETs is achieved due to the improved high exciton utilization and light outcoupling efficiency which is the highest value reported so far for OLETs and prevents exciton-charge annihilation and electrode photon losses. Moreover, good loop stability is also achieved, along with effective gate tunability and ultralow driving voltage of below 5 V. Finally, a 4 × 6 white-emission OLET array for full-color display is demonstrated for the first time, suggesting its great potential applications for advanced display technologies.