Bright, low-voltage driven colloidal quantum dot (QD)-based white light-emitting devices (LEDs) with practicable device performances are enabled by the direct exciton formation within quantum-dot active layers in a hybrid device structure. Detailed device characterization reveals that white-QLEDs can be rationalized as a parallel circuit, in which different QDs are connected through the same set of electrically common organic and inorganic charge transport layers.
Quantum dot light‐emitting diodes (QLEDs) are one of the most promising candidates for next‐generation displays and lighting sources, but they are barely used because vulnerability to electrical and thermal stresses precludes high brightness, efficiency, and stability at high current density (J) regimes. Here, bright and stable QLEDs on a Si substrate are demonstrated, expanding their potential application boundary over the present art. First, a tailored interface is granted to the quantum dots, maximizing the quantum yield and mitigating nonradiative Auger decay of the multiexcitons generated at high‐J regimes. Second, a heat‐endurable, top‐emission device architecture is employed and optimized based on optical simulation to enhance the light outcoupling efficiency. The multilateral approaches realize that the red top‐emitting QLEDs exhibit a maximum luminance of 3 300 000 cd m−2, a current efficiency of 75.6 cd A−1, and an operational lifetime of 125 000 000 h at an initial brightness of 100 cd m−2, which are the highest of the values reported so far.
We fabricated highly efficient iridium(III) bis[(4,6-di-fluorophenyl)-pyridinato-N,C2′] picolinate doped inverted bottom-emission blue phosphorescent organic light-emitting diodes, with an electron injection layer of zinc oxide (ZnO) nanoparticles (NPs). The ZnO NPs layer lowers the turn-on voltage by about 4 V and significantly enhances the efficiency. The device with ZnO NPs shows peak efficiencies of 16.5 cd/A and 8.2%, about three times higher than those of the device without ZnO NPs. Since the ZnO NPs layer has a wide band gap, good electron transporting properties and low work function, it can be utilized as an effective electron injection layer with good transparency.
the diode was consisted of printed inorganic layers of Si and NbSi 2 microparticles with an organic binder. [ 8 ] Because the operational frequency of the diode scales with its charge-transporting properties, the realization of the UHF rectifi er based on organic materials has been a challenge. Recently, a rectifi er with a 3 dB frequency reaching an impressive 700 MHz in terms of voltage was demonstrated, but its voltage output ( V out ) at 1 GHz was only 0.31 V for an AC input signal with 2 V amplitude. [ 9 ] In order to achieve ultrahigh frequency performance organic rectifi ers, which commonly consist of diodes and capacitors, it is important to achieve high charge carrier injection effi ciency and mobility within the organic semiconductor layer. Even if the work function of a metal electrode is selected to match the highest occupied molecular orbital (HOMO) level of an organic semiconductor, the formation of an adversely aligned dipole or other (e.g., oxide) interface layer can lead to a hole injection barrier, limiting charge injection. [ 10,11 ] Self-assembled monolayers (SAMs) represent one good candidate for ensuring effi cient charge injection by specifi cally tuning the metal work function. [12][13][14][15] Interfacial charge trapping can also sometimes help. [ 16 ] The permanent dipole moment of suitably selected SAM molecules changes the effective metal work function, reducing the charge injection barrier. SAMs may also be used to enhance the properties of gate dielectric layers in organic thin fi lm transistors (TFTs). [ 17,18 ] In addition to SAM-based metal work function tuning, surface energy characteristics are also altered by the SAM functional groups. This in turn can modify the subsequent deposition of organic semiconductor layers. In particular, pentacene grain formation, one of the important factors determining pentacene thin fi lm mobility, is much affected by substrate surface energy. The SAM molecule functional groups can be selected to lower the surface energy, thereby enhancing molecular packing and improving mobility. [ 19 ] Studies have shown that the orientation of pentacene deposited on Au is different to that deposited on SAM-treated Au. [20][21][22] The effect that such structural differences have on electrical characteristics for transport in the vertical direction (normal to the fi lm plane) has not been investigated to any great extent; the great majority of studies have focused on in-plane transport within TFT structures. [23][24][25] In this study, we investigated vertical diode structures instead of TFTs and as a result of the understanding gained we were able to fabricate ultrafast pentacene rectifi ers with V out = 3.8 V at 1 GHz and with a 3 dB frequency, in terms of voltage, of 1.24 GHz, the highest value reported to date. [ 8 ] Conjugated organic molecules such as pentacene, demonstrate strong electron-vibrational mode coupling with a dependence on orientation. This allows us to use Raman spectroscopy as a probe for molecular orientation. [ 26 ] Here, For automatic det...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.