An estimate of the inter-system crossing time in light-emitting polymers

Scattering and Recombination of Two Triplet Excitons in polymer light-emitting diodes

The scattering and recombination processes between two triplet excitons in conjugated polymers are investigated by using a nonadiabatic evolution method, based on an extended Su-Schrieffer-Heeger model including interchain interactions. Due to the interchain coupling, the electron and/or hole in the two triplet excitons can exchange. The results show that the recombination induces the formation of singlet excitons, excited polarons and biexcitons. Moreover, we also find the yields of these products, which can contribute to the emission, increase with the interchain coupling strength, in good a…

Theory of the singlet exciton yield in light-emitting polymers

This paper presents a possible explanation for the enhanced singlet exciton yield in light emitting polymers. We propose a theory of electron-hole recombination via inter-molecular inter-conversion from inter-molecular weakly bound polaron pairs (or charge-transfer excitons) to intra-molecular excitons. This theory is applicable to parallel polymer chains. A crucial aspect of the theory is that both the intra-molecular and inter-molecular excitons are effective-particles, which are described by both a relative-particle wavefunction and a center-of-mass wavefunction. This implies two electronic…

单根共轭聚合物链中高效的激子-激子湮灭

Highly efficient exciton-exciton annihilation in single conjugated polymer chains

本研究通过测量聚芴单链的时间分辨光子统计，发现单根共轭聚合物链可承载的独立激子数量极少，揭示了高效激子-激子湮灭效应，为调控该效应以提升共轭聚合物光电应用性能提供了依据。

环聚合物表面跳跃中的受挫跳跃：实时动力学与细致平衡

Frustrated hops in Ring Polymer Surface Hopping: Real-time dynamics and detailed balance

本文研究了RPSH方法中的能量守恒与细致平衡问题，通过Tully避免交叉模型等系统探究受挫跳跃的处理，证明其是准确描述实时动力学和重现量子Boltzmann布居数的关键。

Model for Triplet State Engineering in Organic Light Emitting Diodes

Engineering the position of the lowest triplet state (T1) relative to the first excited singlet state (S1) is of great importance in improving the efficiencies of organic light emitting diodes and organic photovoltaic cells. We have carried out model exact calculations of substituted polyene chains to understand the factors that affect the energy gap between S1 and T1. The factors studied are backbone dimerisation, different donor-acceptor substitutions and twisted geometry. The largest system studied is an eighteen carbon polyene which spans a Hilbert space of about 991 million. We show that …

Fluorescence via Reverse Intersystem Crossing from Higher Triplet States in a Bisanthracene Derivative

To elucidate the high external quantum efficiency observed for organic light-emitting diodes using a bisanthracene derivative, BD1, as the emitting molecule, off-diagonal vibronic coupling constants (VCCs) between the excited states of BD1, which govern non-radiative transition rates, were calculated employing time-dependent density functional theory. The VCCs were analysed based on the concept of vibronic coupling density. The VCC calculations suggest a fluorescence via higher triplets (FvHT) mechanism, which entails the conversion of a T$_4$ exciton generated during electrical excitation int…