研究目的
Investigating the effects of chromophore rigidity/flexibility on the efficiency of thermally activated delayed fluorescence (TADF) in blue emitters.
研究成果
The study demonstrated that the efficiency of TADF enhances in the series DPA < Az < Ac, with the high efficiency of the acridine-based emitters originating in the relative planarity of acridine. The results shed new light on important issues to consider in designing TADF emitters, including the balance of electron donating/accepting strength and the relative rigidity of the D and A units.
研究不足
The study is limited by the specific choice of donor and acceptor molecules and the conditions under which the photophysical properties were measured. The photostability of Az-based emitters in chloroform was noted as a limitation.
1：Experimental Design and Method Selection
The study involved the synthesis of four new symmetrical donor?acceptor?donor (D?A?D)-type molecules with diphenylamine (DPA) or 10,11-dihydro-5H-dibenz[b,f ]azepine (Az) as electron donors and 9,9-dimethylthioxanthene-S,S-dioxide (TXO2) as the electron acceptor. The molecules were characterized by X-ray crystallography, photophysical studies, and theoretical calculations.
2：Sample Selection and Data Sources
Samples studied included solutions (10?3?10?5 M) and films produced in Zeonex matrix (5 wt %). All solutions were diluted in different solvents and stirred for several hours. Films in the Zeonex matrix were fabricated by drop-casting onto quartz substrates.
3：List of Experimental Equipment and Materials
UV-3600 Shimadzu spectrophotometer, Jobin Yvon Horiba Fluoromax 3, Nd:YAG laser (EKSPLA), nitrogen laser, spectrograph, sensitive gated iCCD camera (Stanford Computer Optics).
4：Experimental Procedures and Operational Workflow
Steady-state absorption and emission spectra were acquired. Time-resolved spectra were obtained by exciting the sample with a Nd:YAG laser or a nitrogen laser. Phosphorescence, prompt fluorescence (PF), and delayed fluorescence (DF) spectra and decays were recorded using nanosecond gated luminescence and lifetime measurements.
5：Data Analysis Methods
Computations were performed with the Gaussian 09 package using different density functional theory (DFT) methods. The isolated molecules were optimized at the rBMK/6-31G(d) level in the gas phase. The spectroscopic properties of the molecules were calculated by means of time dependent DFT (TD-DFT) calculations employing the 6-31G(d) basis set.
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