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Effect of exciton diffusion on the triplet-triplet annihilation rate in organic semiconductor host-guest systems
摘要： We study the contribution of triplet exciton diffusion to the efficiency loss resulting from F?rster-type triplet-triplet annihilation (TTA) in organic phosphorescent semiconductor host-guest systems, using kinetic Monte Carlo (KMC) simulations. Our study focusses on diffusion due to F?rster-type guest-guest transfer, but includes also a comparison with simulation results for the case of Dexter-type guest-guest transfer. The simulations are carried out for a wide range of F?rster radii, and for guest concentrations up to 100 mol%, with the purpose to support analyses of time-resolved photoluminescence experiments probing TTA. We find that the relative contribution of diffusion to the TTA-induced efficiency loss may be deduced quite accurately from a quantitative experimental measure for the shape of the time-dependent photoluminescence intensity, the so-called r ratio. For small guest concentrations and F?rster radii that are most relevant to organic light-emitting diodes (OLEDs), the diffusion contribution is in general quite small. Under these weak-diffusion conditions, the absolute diffusion contribution to the TTA-induced efficiency loss can be understood quantitatively using a capture radius formalism. The effective guest-guest diffusion coefficient that follows from the TTA simulations, using the capture radius formalism, agrees well with the diffusion coefficient that follows from direct KMC diffusion simulations. The simulations reveal that the diffusion coefficient is strongly affected by the randomness of the distribution of guest molecule locations.
关键词： OLEDs,photoluminescence,kinetic Monte Carlo simulations,Dexter transfer,organic semiconductors,triplet-triplet annihilation,exciton diffusion,host-guest systems,F?rster transfer
更新于2025-09-23 15:23:52
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A New Biscarbazole-Based Metal-Organic Framework for Efficient Host-Guest Energy Transfer
摘要： A new metal–organic framework (MOF), [Zn6L4(Me2NH2+)4·3 H2O] (1) was constructed based on [9,9’-biscarbazole]-3,3’,6,6’-tetracarboxylic acid (H4L) and Zn2+ ions. The porous framework and intense blue fluorescence of the MOF based on the biscarbazole moiety of the ligand could facilitate efficient host to guest energy transfer, which makes it an ideal platform for the tuning of luminescence.
关键词： in situ encapsulation,metal–organic frameworks,energy transfer,host–guest systems,fluorescence
更新于2025-09-23 15:23:52
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Photoswitchable Host-Guest Systems Incorporating Hemithioindigo and Spiropyran Units
摘要： We cover selected examples of the incorporation of hemithioindigo and spiropyran units in one of the binding partners of synthetic host-guest systems. In some of the simplest systems, isomerization of the switch simply modulates the thermodynamic stability of the two isomeric host-guest complexes. In the presence of more than two binding partners, the isomerization of the molecular switch alters the composition of the multicomponent host-guest system producing a shuttling process of one of the components between different hosts. In others, the isomerization process controls the uptake and release of some of the components from/to the bulk solution. We show that the understanding of the isomerization mechanisms of the molecular switches and the effects produced by the external stimuli are essential for the design of complex and responsive supramolecular host-guest systems. The physicochemical properties of the hemithioindigo and spiropyran molecular photoswitches are complementary, providing different avenues to their applications in solution and material science.
关键词： Spiropyrans,Hemithioindigos,Host-Guest Systems,Supramolecular Assemblies,Photoswitches
更新于2025-09-23 15:22:29