Improving the Electroluminescent Performance of Blue Light-Emitting Polymers by Side-Chain Modification

Achieving Bright Organic Light-Emitting Field-Effect Transistors with Sustained Efficiency through Hybrid Contact Design

Organic light-emitting field-effect transistors (OLEFETs) with bilayer structures have been widely studied due to their potential to integrate high-mobility organic transistors and efficient organic light-emitting diodes. However, these devices face a major challenge of imbalance charge transport, leading to a severe efficiency roll-off at high brightness. Here, we propose a solution to this challenge by introducing a transparent organic/inorganic hybrid contact with specially designed electronic structures. Our design aims to steadily accumulate the electrons injected into the emissive polymer, allowing the light-emitting interface to effectively capture more holes even when the hole current increases. Our numerical simulations show that the capture efficiency of these steady electrons will dominate charge recombination and lead to a sustained external quantum efficiency of 0.23% over 3 orders of magnitude of brightness (4 to 7700 cd/m²) and current density (1.2 to 2700 mA/cm²) from -4 to -100 V. The same enhancement is retained even after increasing the external quantum efficiency (EQE) to 0.51%. The high and tunable brightness with stable efficiency offered by hybrid-contact OLEFETs makes them ideal light-emitting devices for various applications. These devices have the potential to revolutionize the field of organic electronics by overcoming the fundamental challenge of imbalance charge transport.

Flexible Double-Sided Light-Emitting Devices Based on Transparent Embedded Interdigital Electrodes

In the areas of flexible displays and wearable devices, double-sided light-emitting devices have huge commercial applications. Here, we provide a novel form of flexible double-sided light-emitting devices by designing and manufacturing different transparent interdigital electrodes for lighting the structural areas of composite emitting layers. The transparent interdigital electrodes are fabricated by embedding multiwalled carbon nanotubes in interdigital mesh-structured microcavities using a doctor-blading process, and the emitting layers are fabricated by mixing copper-doped zinc sulfide (ZnS/Cu) phosphor particles with the transparent polydimethylsiloxane polymer. The fabricated double-sided light-emitting devices could be in the crimp state, exhibiting excellent flexibility. By designing the structure of the interdigital electrodes and the thickness of the emitting layers, the double-sided emission intensity of the light-emitting devices can be adjusted. Furthermore, based on the flexible double-sided light-emitting devices, various patterns can be successfully programed, such as the digital, grayscale, and ancient Chinese walls. The flexible and programmable double-sided light-emitting films provide a promising strategy for the next generation of customized flexible displays.

Improving the Performance of Blue Polymer Light-Emitting Diodes Using a Hole Injection Layer with a High Work Function and Nanotexture

For light-emitting polymers with a deep highest occupied molecular orbital energy level used for polymer light-emitting diodes (PLEDs), the hole injection barrier and hole transport of the anode buffer layer are of vital importance for optimizing electroluminescent performance. In this study, high-work-function hole injection layers with nanotextures were achieved by modifying poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) with a perfluorinated ionomer (PFI) and n-butyl alcohol and were used to achieve a single-layer device without a hole transport layer. With such an interlayer, the PLEDs based on PPF-SO25 exhibit remarkable current efficiency over 13.0 cd A^-1, which significantly outperform the devices with regular PEDOT:PSS. To our knowledge, this performance is among the best reported for single-layer blue PLEDs. The bias-dependent capacitance curves of these PLEDs suggest a nonuniform surface distribution of PFI. Our findings show that the PFI-modified PEDOT:PSS not only operates as a high-work-function hole injection layer to facilitate hole injection but also as a potential inner scattering medium for light extraction.