Rapid predictions of the colour purity of luminescent organic molecules
Rapid predictions of the colour purity of luminescent organic molecules
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DOI：
10.1039/d1tc04748e
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发表时间：
2022-01-07
影响因子：
6.4
通讯作者：
Penfold, Thomas J.
中科院分区：
文献类型：
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作者：
Ahmad, Shawana A.;Eng, Julien;Penfold, Thomas J.
设计呈现窄带发射的发光有机材料对于实现高分辨率和节能的有机发光二极管（OLED）是至关重要的，但仍然是一个重大挑战。本文建立了27个有机功能分子的发光半峰全宽（FWHM）的决定因素，这些有机功能分子具有不同的发光特性，包括π-π *、电荷转移和多重共振。我们表明，发射半高宽可以解释内的位移谐振子模型（DHO），这意味着预测可以使用基态频率和激发态梯度计算。这消除了对激发态几何形状和海森的耗时计算的需要。虽然形式上仅在Condon近似内有效，但DHO模型为表现出显着Herzberg-Teller效应的光谱提供了合理的相关性，不仅可以预测发射FWHM，而且还可以告知负责发射带加宽的正常模式。此外，三个多共振型热激活延迟荧光（TADF）发射器的量子化学和速率计算表明，当硫在B-N框架内使用时，直接系间交叉（ISC）的重要性可以增加。总体而言，这项工作提供了新的视角，将考虑到合理的分子设计和高通量筛选程序，旨在开发高效率的发光有机材料的发射半高宽。
Designing luminescent organic materials exhibiting narrowband emission is crucial for achieving high resolution and energy efficient organic light emitting diodes (OLEDs), but remains a significant challenge. Herein we establish the key factors determining the emission full-width at half-maximum (FWHM) of 27 organic functional molecules exhibiting emitting states of different characteristics, including pi-pi*, charge transfer and multiple-resonance. We demonstrate that the emission FWHM can be interpreted within the displaced harmonic oscillator model (DHO), meaning that predictions can be made using ground state frequency and excited state gradient calculations only. This eliminates the need for time consuming calculations of excited state geometries and Hessians. While formally only valid within the Condon approximation, the DHO model provides reasonable correlations for spectra exhibiting significant Herzberg-Teller effects and not only makes it possible to predict emission FWHM, but also informs on the normal modes responsible for emission band broadening. In addition, quantum chemistry and rate calculations of three multiple-resonance type thermally activated delayed fluorescence (TADF) emitters demonstrates how the importance of direct intersystem crossing (ISC) can be increased when sulphur is used within the B-N framework. Overall, this work offers new perspectives for incorporating considerations of emission FWHM into rational molecular design and high-throughput screening procedures aiming to develop high efficiency luminescent organic materials.