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<p>The strong transition dipole-dipole interaction in two-dimensional organic molecular crystals induces the exciton effect between electron and hole spins, resulting in the splitting of the bright exciton state and the dark exciton state. The modulation of bright and dark exciton states has aroused great interest in the field of quantum information applications. Conventional thermally activated delayed fluorescence materials, which rely on spatially separated donor-acceptor structures, often exhibit broad emission spectra and efficiency roll-off. In this work, we demonstrate a temperature-induced transition from dark to bright exciton states within the wetting layer of a two-dimensional organic crystal. By switching the aggregation mode from H-aggregation to Hj-aggregation at low temperature, the non-radiative triplet-like states are effectively converted into radiative singlet-like states. This leads to a remarkable enhancement of the photoluminescence quantum yield and the emergence of superradiance, manifested as an intensified 0-0 emission band and a narrowed linewidth. We thus establishes a strategy for achieving flexible switching between bright and dark exciton states through precise control of molecular packing, which enables the design of specific Hj-aggregates with tailored excited-state coherence. This superradiant system, featuring large oscillator strengths and tunable excitonic properties, provides a new platform for quantum information processing.</p>

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Strong optical emission regulated by exciton state in two-dimensional organic molecular crystals

  • 期刊论文

  • 发表日期：

    2026年6月23日

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  • Yutian Yang,
  • Ting Zheng,
  • Weiwei Zhao,
  • Chenyun Cao,
  • Fang Yang,
  • Hongwei Liu,
  • Zhenhua Ni,
  • Junpeng Lu

摘要

The strong transition dipole-dipole interaction in two-dimensional organic molecular crystals induces the exciton effect between electron and hole spins, resulting in the splitting of the bright exciton state and the dark exciton state. The modulation of bright and dark exciton states has aroused great interest in the field of quantum information applications. Conventional thermally activated delayed fluorescence materials, which rely on spatially separated donor-acceptor structures, often exhibit broad emission spectra and efficiency roll-off. In this work, we demonstrate a temperature-induced transition from dark to bright exciton states within the wetting layer of a two-dimensional organic crystal. By switching the aggregation mode from H-aggregation to Hj-aggregation at low temperature, the non-radiative triplet-like states are effectively converted into radiative singlet-like states. This leads to a remarkable enhancement of the photoluminescence quantum yield and the emergence of superradiance, manifested as an intensified 0-0 emission band and a narrowed linewidth. We thus establishes a strategy for achieving flexible switching between bright and dark exciton states through precise control of molecular packing, which enables the design of specific Hj-aggregates with tailored excited-state coherence. This superradiant system, featuring large oscillator strengths and tunable excitonic properties, provides a new platform for quantum information processing.