33‐4: Invited Paper: A Chemical Structure Approach Enhancing Light Outcoupling of Dopant OLEDs and Internal Quantum Efficiency of Non‐Dopant OLEDs Having Bluish TADF Emitters
Yi‐Ting LeePo-Chen TsengTakeshi KominoMasashi MamadaJiun‐Haw LeeChihaya AdachiChao-Tsen ChenChin‐Ti Chen
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Dopant and non‐dopant OLEDs were fabricated for testing four TADF emitters, having EL of blue to greenish blue color. The tetraphenylbenzene (4Ph)‐containing emitters have been demonstrated having a higher light outcoupling efficiency for dopant devices and a superior IQE for the non‐dopant devices.Keywords:
Quantum Efficiency
Two types of the organic light-emitting devices (OLEDs) with different emission structures were prepared using Alq3 (aluminum tris 8-hydroxyquinoline) host material and quinacridone (QD) dopant at the emission layer. One is the OLED device with emission layer consisting of Alq3 host material doped with QD dopant ("codoped OLED"). The another one has a seperated QD dopant film in the Alq3 emission layer ("undoped OLED"). The maximum brightness of the codoped and undoped OLEDs were 3207 cd/m2 and 1570 cd/m2, respectively. The wavelength of the maximum emission peak in the undoped sample was 527 nm and shifted slightly toward longer wavelength with the value of 540 nm for the codoped OLED sample. The maximum luminous efficiency of the undoped OLED was about 1.4 lm/W and increased to 7.0 lm/W for the codoped sample.
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The ability to incorporate a dopant element into silicon nanocrystals (NC) and quantum dots (QD) is one of the key technical challenges for the use of these materials in a number of optoelectronic applications. Unlike doping of traditional bulk semiconductor materials, the location of the doping element can be either within the crystal lattice (c-doping), on the surface (s-doping) or within the surrounding matrix (m-doping). A review of the various synthetic strategies for doping silicon NCs and QDs is presented, concentrating on the efficacy of the synthetic routes, both in situ and post synthesis, with regard to the structural location of the dopant and the doping level. Methods that have been applied to the characterization of doped NCs and QDs are summarized with regard to the information that is obtained, in particular to provide researchers with a guide to the suitable techniques for determining dopant concentration and location, as well as electronic and photonic effectiveness of the dopant.
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The process of p-type doping for GaN nanowires is investigated using calculations starting from first principles. The influence of different doping elements, sites, types, and concentrations is discussed. Results suggest that Mg is an optimal dopant when compared to Be and Zn due to its stronger stability, whereas Be atoms are more inclined to exist in the interspace of a nanowire. Interstitially-doped GaN nanowires show notable n-type conductivity, and thus, Be is not a suitable dopant, which is to be expected since systems with inner substitutional dopants are more favorable than those with surface substitutions. Both interstitial and substitutional doping affect the atomic structure near dopants and induce charge transfer between the dopants and adjacent atoms. By altering doping sites and concentrations, nanowire atomic structures remain nearly constant. Substitutional doping models show p-type conductivity, and Mg-doped nanowires with doping concentrations of 4% showing the strongest p-type conductivity. All doping configurations are direct bandgap semiconductors. This study is expected to direct the preparation of high-quality GaN nanowires.
Wide-bandgap semiconductor
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Abstract Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical even today. Co-doping is a promising strategy that can be used for effectively tuning the dopant populations, electronic properties, and magnetic properties. It can enhance the solubility of dopants and improve the stability of desired defects. During the past 20 years, significant experimental and theoretical efforts have been devoted to studying the characteristics of co-doping. In this article, we first review the historical development of co-doping. Then, we review a variety of research performed on co-doping, based on the compensating nature of co-dopants. Finally, we review the effects of contamination and surfactants that can explain the general mechanisms of co-doping.
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Doping strategy has been applied in lots of areas holding promising performance for many functions. Here, we systemically report the main trends in structural, electronic properties and chemical bonding for V doped into 2H-NbSe2 in two types of doping by means of the first-principles PBE-GGA calculations. To investigate the stability of the doped system with changing concentration of V atoms, 2 × 2 × 1, 3 × 3 × 1 and 4 × 4 × 1 2H-NbSe2 supercells have been taken into consideration. Results show that it is easier to be doped as the concentration of dopant V is lower and the substituted doping structure is more stable than that of the dopant embedded into the interlayer. In addition, it is found that the dopant V atom forms a covalent bond with the surrounding Se atoms in both of the two doping structures, which can explain the variations of the structural parameters after V atom is doped into 2H-NbSe2. Moreover, what leads to the variation of the electronic structures is that the asymmetric structure and the more energetic Se atoms firstly near the dopant V atom after V is doped into 2H-NbSe2 in both of the two doping types. Our calculation results can provide good theoretical knowledge for the subsequent experiments.
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As well as understanding the location of dopants in optical materials, it is also important to understand how much dopant can be added to a given material. A method for calculating the maximum concentration of dopants has been developed, and applied to dopants in mixed metal fluorides for optical and nuclear clock applications. Applications to rare earth doping in YLiF4, and Th doping in LiCaAlF6/LiSrAlF6 are described, and compared with available experimental data.
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A new kind of non-doping red OLED was fabricated, using partially conjugated PPV as hole-transport material and non-doping DCM as emitter. The new OLED shows good performance of pure red luminescence
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Non-equilibrium Approach to Doping of Wide Bandgap materials by Molecular Beam Epitaxy. Final Report
It is well known that it has been difficult to obtain good bipolar doping in a wide bandgap semiconductors. Developed a new doping technique, involving use of a standard dopant, together with a ''co-dopant'' used to facilitate the introduction of the dopant, and have vastly alleviated this problem.
Wide-bandgap semiconductor
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