Extremely Simplified, High-Performance, and Doping-Free White Organic Light-Emitting Diodes Based on a Single Thermally Activated Delayed Fluorescent Emitter

For the first time, extremely simplified yet high-performance thermally activated delayed fluorescent (TADF) white organic light-emitting diodes (WOLEDs) have been demonstrated. Unlike previous concepts, only a single molecular emitter is required for high-quality white emissions, where an intrinsic TADF emitter is sandwiched between p-type and n-type layers, forming a doping-free p-i-n WOLED. The WOLED exhibits a color rendering index (CRI) of 91, the first WOLED that overtakes its counterparts (single-emitter white polymer/inorganic LEDs). The maximum total external quantum efficiency (28.4%) and power efficiency (68.5 lm W^–1) are comparable to those of state-of-the-art doped TADF WOLEDs and doping-free phosphorescent WOLEDs and higher than those of TADF WOLEDs with ultrahigh CRIs (≥90) and high-quality single-emitter white LEDs. Significantly, this is the first TADF WOLED possessing ultrahigh CRIs at high luminance, and 18 796 cd m^–2 is 370% higher than that of the previous best-performing one. Moreover, the proposed WOLED is the simplest TADF WOLED

High-Performance Blue Molecular Emitter-Free and Doping-Free Hybrid White Organic Light-Emitting Diodes: an Alternative Concept To Manipulate Charges and Excitons Based on Exciplex and Electroplex Emission

For the first time, hybrid white organic light-emitting diodes (WOLEDs) have been developed via the manipulation of exciplex and electroplex emission. Unlike previous hybrid WOLEDs, this novel kind of hybrid WOLED is exciplex/electroplex based hybrid WOLEDs. First, an exciplex/electroplex system is explored, exhibiting the best performance among WOLEDs with emissions generated from exciplex/electroplex systems. Then, with doping-free technology, the single-molecular-emitter WOLED exhibits maximum total external quantum efficiency (EQE) and power efficiency (PE) of 16.8% and 56.4 lm W^–1, respectively, the highest among doping-free hybrid WOLEDs. Besides, PE at 1000 cd m^–2 (40.0 lm W^–1) is higher/efficiency roll-off is lower than some best doping hybrid WOLEDs. The two-molecular-emitter WOLED exhibits (i) a CRI of 92.1, the highest among doping-free WOLEDs (DF-WOLEDs); (ii) a correlated color temperature of 2319 K, the lowest among DF-WOLEDs; and (iii) 2-fold higher efficiency (28.2 lm W^–1) than the best DF-WOLEDs with ultrahigh color rendering index (CRI > 90). Moreover, the exciplex/electroplex system can be demonstrated to doping hybrid WOLEDs, achieving the EQE and PE of 20.0% and 52.7 lm W^–1 at 1000 cd m^–2, respectively, comparable to the best hybrid WOLEDs. Such findings may (i) be the first report that the performance of doping-free hybrid WOLEDs is comparable to that of doping hybrid WOLEDs, (ii) open a new opportunity that a family of materials generating exciplex/electroplex emissions are promising for hybrid WOLEDs, (iii) unlock an alternative concept to develop hybrid WOLEDs, regardless of doping-free or doping structures

Inorganic–Organic Dual-Ligand-Regulated Photocatalysis of CdS@Zn_<i>x</i>Cd_1–<i>x</i>S@ZnS Quantum Dots for Lignin Valorization

In a dual-functional lignin valorization system, a harmonious oxidation and reduction rate is a prerequisite for high photocatalytic performance. Herein, an efficient and facile ligand manipulating strategy to balance the redox reaction process is exploited via decorating the surface of the CdS@ZnxCd1–xS@ZnS gradient-alloyed quantum dots with both inorganic ligands of hexafluorophosphate (PF6–) and organic ligands of mercaptopropionic acid (MPA). Inorganic ion ligands in this system provide a promotion for intermediator reduction reactions. By optimizing the ligand composition on the quantum dot surface, we achieve precise control over the extent of oxidation and reduction, enabling selective modification of reaction products; that is, the conversion rate of 2-phenoxy-1-phenylethanol reached 99%. Surface engineering by regulating the ligand type demonstrates that PF6– and thiocyanate (SCN–) inorganic ion ligands contribute significantly toward electron transfer, while MPA ligands have beneficial effects on the hole-transfer procedure, which is predominantly dependent on their steric hindrance, electrostatic action, and passivation effect. The present study offers insights into the development of efficient quantum dot photocatalysts for dual-functional biomass valorization through ligand design

Damage-Free Back Channel Wet-Etch Process in Amorphous Indium–Zinc-Oxide Thin-Film Transistors Using a Carbon-Nanofilm Barrier Layer

Amorphous indium–zinc-oxide thin film transistors (IZO-TFTs) with damage-free back channel wet-etch (BCE) process were investigated. A carbon (C) nanofilm was inserted into the interface between IZO layer and source/drain (S/D) electrodes as a barrier layer. Transmittance electron microscope images revealed that the 3 nm-thick C nanofilm exhibited a good corrosion resistance to a commonly used H₃PO₄-based etchant and could be easily eliminated. The TFT device with a 3 nm-thick C barrier layer showed a saturated field effect mobility of 14.4 cm² V^–1 s^–1, a subthreshold swing of 0.21 V/decade, an on-to-off current ratio of 8.3 × 10¹⁰, and a threshold voltage of 2.0 V. The favorable electrical performance of this kind of IZO-TFTs was due to the protection of the inserted C to IZO layer in the back-channel-etch process. Moreover, the low contact resistance of the devices was proved to be due to the graphitization of the C nanofilms after annealing. In addition, the hysteresis and thermal stress testing confirmed that the usage of C barrier nanofilms is an effective method to fabricate the damage-free BCE-type devices with high reliability

Tunable Polarity Behavior and High-Performance Photosensitive Characteristics in Schottky-Barrier Field-Effect Transistors Based on Multilayer WS₂

Schottky-barrier field-effect transistors (SBFETs) based on multilayer WS₂ with Au as drain/source contacts are fabricated in this paper. Interestingly, the novel polarity behavior of the WS₂ SBFETs can be modulated by drain bias, ranging from p-type to ambipolar and finally to n-type conductivity, due to the transition of band structures and Schottky-barrier heights under different drain and gate biases. The electron mobility and the on/off ratio of electron current can reach as high as 23.4 cm²/(V s) and 8.5 × 10⁷, respectively. Moreover, the WS₂ SBFET possesses high-performance photosensitive characteristics with response time of 40 ms, photoresponsivity of 12.4 A/W, external quantum efficiency of 2420%, and photodetectivity as high as 9.28 × 10¹¹ cm Hz^1/2/W. In conclusion, the excellent performance of the WS₂ SBFETs may pave the way for next-generation electronic and photoelectronic devices