Thermally activated delayed fluorescence materials with aggregation-induced emission properties: a QM/MM study

Enhancing Reverse Intersystem Crossing in Triptycene-TADF Emitters: Theoretical Insights into Reorganization Energy and Heavy Atom Effects

Thermally activated delayed fluorescence (TADF) emitters based on the triptycene skeleton demonstrate exceptional performance, superior stability, and low efficiency roll-off. Understanding the interplay between the luminescent properties of triptycene-TADF molecules and their assembly environments, along with their excited-state characteristics, necessitates a comprehensive theoretical exploration. Herein, we predict the photophysical properties of triptycene-TADF molecules in a thin film environment using the quantum mechanics/molecular mechanics method and quantify their substantial dependency on the heavy atom effects and reorganization energies using the Marcus-Levich theory. Our calculated photophysical properties for two recently reported molecules closely align with experimental values. We design three novel triptycene-TADF molecules by incorporating chalcogen elements (O, S, and Se) to modify the acceptor units. These newly designed molecules exhibit reduced reorganization energies and enhanced reverse intersystem crossing (RISC) rates. The heavy atom effect amplifies spin-orbit coupling, thereby facilitating the RISC process, particularly at a remarkably high rate of ∼109 s-1.

Designing thermally activated delayed fluorescence emitters with through-space charge transfer: a theoretical study

Recently, thermally activated delayed fluorescence (TADF) molecules with through-space charge transfer (TSCT) features have been widely applied in developing organic light-emitting diodes with high luminescence efficiencies. The performance of TSCT-TADF molecules depends highly on their molecular structures. Therefore, theoretical investigation plays a significant role in designing novel highly efficient TSCT-TADF molecules. Herein, we theoretically investigate two recently reported TSCT-TADF molecules, 1'-(2,12-di-t-butyl[1,4]benzoxaborinino[2,3,4-kl]phenoxaborinin-7-yl)-10-phenyl-10H-spiro[acridine-9,9'-fluorene] (AC-BO) and 1-(2,12-di-t-butyl[1,4]benzoxaborinino[2,3,4-kl]phenoxaborinin-7-yl)-9',9'-dimethyl-9'H-spiro [fluorene-9,5'-quinolino[3,2,1-de]acridine](QAC-BO). The calculated photophysical properties (e.g. excited state energy levels and luminescence properties) for these two compounds are in good agreement with experimental data. Based on the systematic analysis of structure-performance relationships, we design three novel TSCT-TADF molecules with high molecular rigidity and evident TSCT features, i.e., DQAC-DBO, DQAC-SBO, and DQAC-NBO. They exhibit deep-blue light emissions and fast reverse intersystem crossing rates (KRISCs). Our calculations demonstrate that the nearly coplanar orientation of the donor and acceptor is critical to achieve remarkable KRISCs and fluorescence efficiencies in TSCT-TADF molecules.

The luminescent and reaction mechanisms of a fluorescent probe for the detection of hypochlorous acid: Insights from theory

We have designed and synthesized a novel fluorescent probe BMH for detection of hypochlorous acid (HClO), which can increase dramatically the fluorescence intensity and had ultrafast response, a low detection limit and a wide pH range of application. In this paper, we further studied its fluorescence quantum yield and photoluminescence mechanism theoretically. The calculated results indicated the first excited states of BMH and BM (it was the oxidized product by HClO) were bright states with large oscillator strengths, however, due to more larger reorganization energy of BMH, the predicted internal conversion rate k_IC of BMH was four orders of magnitude larger than that of BM; moreover, owing to the effect of heavy atom from sulfur atom in BMH, the predicted intersystem crossing rate k_isc of BMH was five orders of magnitude larger than that of BM; meanwhile there was no significant difference found between both the predicted radiative rates k_r, thus the calculated fluorescence quantum yield of BMH was nearly zero and that of BM was more than 90%, the data showed the BMH had no fluorescence but its oxidated produce BM possessed strong fluorescence. In addition, the reaction mechanism of BMH transforming into BM has been investigated too, according to the potential energy profile, we found that the course of BMH converting into BM consisted of three elementary reactions. The research results revealed the solvent effect can decreased the activation energy, which was more favorable for these elementary reactions.

Carbonyl (CO)/N-based thermally activated delayed fluorescent materials with high efficiency and fast reverse intersystem crossing rate: a theoretical design and study

Two novel highly efficient organic TADF materials based on MR structures have been theoretically designed and investigated.

Theoretically elucidating high photoluminescence performance of dimethylacridan-based blue-color thermally activated delayed fluorescent materials

Based on first-principles methods, we comprehensively quantify the luminous quantum efficiencies and related photophysical process rates of dimethylacridan-based blue-color TADF emitters.