External heavy atom effect in brominated carbazole/oxadiazole hybrid hosts for enhanced efficiency in phosphorescence and TADF OLEDs

IF 4.1 3区工程技术 Q2 CHEMISTRY, APPLIED

Dyes and Pigments Pub Date : 2025-04-10 DOI:10.1016/j.dyepig.2025.112822

Jingsheng Wang , Shiying Hu , Yuying Wu, Yaotian Zhang, Yeting Tao, Youtian Tao

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引用次数: 0

Abstract

The influence of heavy atom effects in organic host materials has been rarely explored in organic light-emitting diodes (OLEDs). In this study, we present four novel carbazole/oxadiazole hybrid bipolar transport host materials with heavy bromine atom substitution: the asymmetric Cz-3BrCzOXD and Cz-4BrCzOXD, and the symmetric o-3BrCzOXD and o-4BrCzOXD. By introducing one or two bromine atoms at the 3- or 4-position of the carbazole units, all brominated hosts exhibited similar energy levels, while demonstrating enhanced hole transport and a slight reduction in electron transport compared to the bromine-free control material, o-CzOXD. When doped with either phosphorescent or thermally activated delayed fluorescence (TADF) dopants, the brominated hosts demonstrated enhanced intersystem crossing (ISC) rates, leading to more efficient exciton utilization. Consequently, compared to o-CzOXD, both phosphorescent and TADF OLEDs exhibited improved device efficiencies for all four brominated hosts. The maximum external quantum efficiencies increased from 20.9 % to 24.3 % for green phosphorescent (ppy)₂Ir(acac) OLEDs, from 20.3 % to 24.5 % for green TADF 4tCzDOXD OLEDs, and from 21.3 % to 24.9 % for light-blue TADF dCF₃5tCzOXD OLEDs. Our findings indicate that the external heavy atom effect offers an effective strategy for enhancing the efficiency of both phosphorescent and TADF OLEDs.

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外重原子效应对溴化咔唑/恶二唑杂交寄主磷光和TADF oled效率的影响

在有机发光二极管中，重原子效应对有机主体材料的影响很少被研究。在这项研究中，我们提出了四种新的重溴原子取代的咔唑/恶二唑杂化双极输运宿主材料：不对称的Cz-3BrCzOXD和Cz-4BrCzOXD，以及对称的o-3BrCzOXD和o-4BrCzOXD。通过在咔唑单元的3位或4位上引入一个或两个溴原子，所有溴化宿主都表现出相似的能级，同时与不含溴的对照材料o-CzOXD相比，显示出增强的空穴传输和略微降低的电子传输。当掺杂磷光或热激活延迟荧光（TADF）掺杂剂时，溴化宿主表现出增强的系统间交叉（ISC）速率，导致更有效的激子利用。因此，与o-CzOXD相比，磷光和TADF oled在所有四种溴化主体上都表现出更高的器件效率。绿色磷光（ppy）2Ir(acac) oled的最大外量子效率从20.9%提高到24.3%，绿色TADF 4tCzDOXD oled的最大外量子效率从20.3%提高到24.5%，浅蓝色TADF dCF35tCzOXD oled的最大外量子效率从21.3%提高到24.9%。我们的研究结果表明，外部重原子效应为提高磷光和TADF oled的效率提供了一种有效的策略。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Dyes and Pigments 工程技术-材料科学：纺织

CiteScore

8.20

自引率

13.30%

发文量

933

审稿时长

33 days

期刊介绍： Dyes and Pigments covers the scientific and technical aspects of the chemistry and physics of dyes, pigments and their intermediates. Emphasis is placed on the properties of the colouring matters themselves rather than on their applications or the system in which they may be applied. Thus the journal accepts research and review papers on the synthesis of dyes, pigments and intermediates, their physical or chemical properties, e.g. spectroscopic, surface, solution or solid state characteristics, the physical aspects of their preparation, e.g. precipitation, nucleation and growth, crystal formation, liquid crystalline characteristics, their photochemical, ecological or biological properties and the relationship between colour and chemical constitution. However, papers are considered which deal with the more fundamental aspects of colourant application and of the interactions of colourants with substrates or media. The journal will interest a wide variety of workers in a range of disciplines whose work involves dyes, pigments and their intermediates, and provides a platform for investigators with common interests but diverse fields of activity such as cosmetics, reprographics, dye and pigment synthesis, medical research, polymers, etc.