Chem. J. Chinese Universities ›› 2026, Vol. 47 ›› Issue (5): 20250414.doi: 10.7503/cjcu20250414

• Review • Previous Articles     Next Articles

Ultra-slow Phonon Dynamics in Organic Aggregated Luminescent Systems and Their Impact on Excited-state Processes

LIU Liqun, TANG Yipeng, WANG Xu, HU Bin()   

  1. State Key Laboratory of Luminescent Materials and Devices,South China University of Technology,Guangzhou 510641,China
  • Received:2025-12-31 Online:2026-05-10 Published:2026-03-13
  • Contact: HU Bin E-mail:bhu@scut.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(T2550060);the National Natural Science Foundation of China(U25A20504)

Abstract:

In the conventional framework of organic optoelectronics, strong electron-phonon coupling between excited-state electrons and molecular vibrations or lattice phonons typically leads to ultrafast nonradiative energy dissipation, thereby limiting further improvements in emission efficiency and device performance. To address this challenge, extensive efforts over the past decade have focused on suppressing nonradiative transitions by weakening nonadiabatic electron-phonon coupling channels through molecular rigidification, conformational restriction, and structural regulation at the material and device levels. Recent studies, however, have demonstrated that phonon dynamics in organic systems with highly ordered aggregate structures do not necessarily proceed on ultrafast timescales. Using experimental approaches such as photoexcitation-modulated Raman spectroscopy, anomalously slow phonon relaxation behaviors extending from milliseconds to seconds have been observed in specific ordered aggregates. Subsequent kinetic investigations reveal that when phonon relaxation is significantly slowed, the rate of nonradiative energy transfer from excited-state electrons to the lattice becomes constrained by the phonon dynamical timescale. As a result, excited-state lifetime is kinetically prolonged and the evolution pathways of excited states are effectively reshaped. In parallel, in ordered donor-acceptor aggregate systems, the cooperative interplay between intermolecular charge-transfer excited states and polar-ordered structures can induce an unconventional form of spin-orbit coupling that is distinct from the traditional heavy-atom mechanism. Rather than originating from atomic relativistic effects, this unconventional spin-orbit coupling manifests as polarization-stabilized spin-mixing and spin-conversion channels acting on excited-state dynamics, which can be experimentally probed through dynamical observables such as magnetic-field-modulated photoluminescence. This review systematically summarizes the conventional physical picture of electron-phonon-coupling-induced nonradiative decay in aggregated organic luminescent systems and outlines the major molecular-, material-, and device-level strategies developed to suppress nonradiative loss. It further highlights recent representative advances in anomalously slow phonon dynamics and their role in regulating excited-state timescales, as well as unconventional spin-orbit coupling phenomena induced by charge-transfer states and polar-ordered structures. On this basis, we introduce the concept of a “phonon-gain optoelectronic effect”, in which phonons are regarded not only merely as energy dissipation channels but also as active regulators of excited-state dynamics. This framework emphasizes the modulation of phonon relaxation rates and aggregate structural order parameters as a multidimensional strategy for controlling excited-state processes in organic optoelectronic systems.

Key words: Aggregated luminescence, Electron-phonon coupling, Ultra-slow Phonon Dynamics, Phonon-gain optoelectronic effect

CLC Number: 

TrendMD: