空间电荷转移型热激活延迟荧光性能的理论研究

doi:10.6023/A26040128

摘要/Abstract

本研究基于密度泛函理论(DFT)和极化连续介质模型(PCM), 以实验报道的高效分子3Ph-SPT为起点, 通过理论设计构建了Ph2Ad-SPT、Ph2Ad-SDT与Ph2Ad-SST等一系列衍生分子以揭示中性基团工程与给体原子工程对通过空间电荷转移热激活延迟荧光(TSCT-TADF)材料性能的协同调控机制, 系统分析了它们的几何结构、电子特性、吸收/发射行为、系间窜越(ISC/RISC)过程以及辐射/非辐射衰减动力学. 结果表明, 中性基团工程(以金刚烷苯基替换三联苯)可有效调控激发态能级与几何结构, 将单重态-三重态能隙降至－0.007 eV, 并抑制S₁→S₀的几何弛豫. 进一步的给体原子工程呈现差异化影响: O→2(-CH₃)取代则因增大的ΔE_ST与减弱的SOC而导致性能下降; O→S取代则能协同优化自旋轨道耦合(SOC增至0.132 cm⁻¹)并显著降低重组能, 从而使RISC速率提升至2.10×10⁷ s⁻¹, 展现出超越原型分子的优越性能, 而其在薄膜态初步研究也预期具有优异的TADF性能. 本研究从理论上阐明了通过中性基团工程与给体原子工程来协同调控TSCT-TADF材料性能的微观机制, 为理性设计兼具高激子利用率与高发光效率的非掺杂TADF材料提供了明确的理论指导.

关键词: 空间电荷转移, 热激活延迟荧光, 中性基团工程, 给体原子工程, 密度泛函理论, 激发态动力学

Through-space charge-transfer thermally activated delayed fluorescence (TSCT-TADF) materials have attracted considerable interest due to their considerable potential for high-performance, particularly non-doped organic light-emitting diodes (OLEDs). Introducing neutral bulky shielding groups into TSCT frameworks has been demonstrated as an effective strategy for developing efficient non-doped emitters; however, the precise molecular-level regulatory mechanisms remain to be fully elucidated. In this study, based on density functional theory (DFT) and the polarizable continuum model (PCM), starting from the experimentally reported high-efficiency molecule 3Ph-SPT, a series of derivative molecules including Ph2Ad-SPT, Ph2Ad-SDT, and Ph2Ad-SST were theoretically designed to elucidate the synergistic regulatory effects of "neutral group engineering" and "donor-atom engineering" on the performance of TSCT-TADF materials. A systematic analysis was conducted on their geometric structures, electronic properties, absorption/emission behaviors, intersystem crossing/reverse intersystem crossing (ISC/RISC) processes, as well as radiative and non-radiative decay dynamics. The results indicate that neutral group engineering—replacing the terphenyl unit with a diphenyladamantyl group—effectively tunes the excited-state energy levels and geometries, reducing the singlet-triplet energy gap to －0.007 eV and suppressing excessive S₁→S₀ geometric relaxation. Further donor-atom engineering exhibits distinct effects: O→2(-CH₃) substitution degrades performance owing to an increased ΔE_ST and weakened spin-orbit coupling (SOC), whereas O→S substitution synergistically enhances SOC (to 0.132 cm⁻¹) and markedly reduces the reorganization energy, thereby elevating the RISC rate to 2.10×10⁷ s⁻¹ and demonstrating superior performance over the prototype molecule, furthermore, preliminary investigations in the thin-film state also expect excellent TADF performance. This work theoretically clarifies the microscopic mechanism of synergistically regulating the performance of TSCT-TADF materials through neutral-group engineering and donor-atom engineering, providing clear theoretical guidance for the rational design of non-doped TADF materials that exhibit both high exciton utilization efficiency and high luminescent efficiency.

Key words: through-space charge transfer, thermally activated delayed fluorescence, neutral-group engineering, donor-atom engineering, density functional theory, excited-state dynamics

引用此文

万浩波, 谢文斌, 杨磊, 冉雪琴, 冯全友, 解令海. 空间电荷转移型热激活延迟荧光性能的理论研究[J]. 化学学报, 2026, 84(9): 1475-1486.

Haobo Wan, Wenbin Xie, Lei Yang, Xueqin Ran, Quanyou Feng, Linghai Xie. Theoretical Study on the Performance of Through-Space Charge-Transfer Thermally Activated Delayed Fluorescence[J]. Acta Chimica Sinica, 2026, 84(9): 1475-1486.

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图/表 12

图1. 所研究分子的化学结构

Figure 1. Chemical structure of the investigated molecules

	S₀/S₁
	3Ph-SPT	Ph2Ad-SPT	Ph2Ad-SDT	Ph2Ad-SST
ϕ₁	－60.3/－60.2	－60.6/－66.3	－61.6/－69.5	－61.1/－68.8
ϕ₂	－99.7/－103.0	－101.2/－105.5	－105.3/－122.4	－109.9/－114.3
\|ϕ₁－ϕ₂\|	39.4/42.8	40.6/39.2	43.7/52.9	48.8/45.5
MPP_D	0.035/0.033	0.035/0.034	0.067/0.061	0.052/0.045
MPP_A	0.016/0.016	0.016/0.017	0.016/0.027	0.020/0.022
l	0.530/0.525	0.532/0.527	0.510/0.515	0.544/0.523

表1. 所研究分子在甲苯溶液中S0 和 S1 状态下的选定几何参数(ϕ1和ϕ2单位: (°); l、MPPD和MPPA单位: nm)

Table 1. Selected geometric parameters (ϕ1, ϕ2, l, MPPD, MPPA) of the investigated molecules in toluene solution for the S0 and S1 states (ϕ1 and ϕ2 in (°); l, MPPD, and MPPA in nm)

图2. 3Ph-SPT (a)、Ph2Ad-SPT (b)、Ph2Ad-SDT (c)和Ph2Ad-SST (d)分子在甲苯溶液中的基态几何结构(饱和氢原子未显示)

Figure 2. Ground-state geometric structures of the 3Ph-SPT (a), Ph2Ad-SPT (b), Ph2Ad-SDT (c), and Ph2Ad-SST (d) molecules in toluene solution. (Saturated hydrogen atoms are omitted for clarity)

图3. 3Ph-SPT (a)、Ph2Ad-SPT (b)、Ph2Ad-SDT (c)和Ph2Ad-SST (d)的几何形状分别在S0、S1和T1态之间的变化

Figure 3. Geometric changes between the S0, S1, and T1 states for 3Ph-SPT (a), Ph2Ad-SPT (b), Ph2Ad-SDT (c), and Ph2Ad-SST (d)

图4. 所研究分子的前线分子轨道分布

Figure 4. Frontier molecular orbital distribution of the investigated molecules

	S₀-S₁
	λ_abs/nm	ΔE/eV	Main transition	λ_em/nm	ΔE/eV	Main transition
3Ph-SPT	338	3.67	HOMO→L＋2 (74%)	523	2.37	HOMO→LUMO (98%)
Ph2Ad-SPT	335	3.69	HOMO→L＋3 (91%)	530	2.34	HOMO→LUMO (98%)
Ph2Ad-SDT	284	4.35	H－3→L＋1 (54%)	488	2.54	HOMO→LUMO (97%)
Ph2Ad-SST	283	4.38	HOMO→LUMO (29%)	512	2.42	HOMO→LUMO (98%)

表2. 所研究分子最大吸收和发射波长、垂直激发能及主要轨道贡献

Table 2. Maximum absorption and emission wavelengths, vertical excitation energies, and main orbital contributions of the investigated molecules

图5. 所研究分子的激发态能级

Figure 5. Excited-state energy levels of the investigated molecules

图6. 3Ph-SPT (a)、Ph2Ad-SPT (b)、Ph2Ad-SDT (c)和Ph2Ad-SST (d)基于S0结构在甲苯溶液中S1和T1态的NTO分析

Figure 6. Natural transition orbital (NTO) analysis for the S1 and T1 states (based on S0 structures) of 3Ph-SPT (a), Ph2Ad-SPT (b), Ph2Ad-SDT (c), and Ph2Ad-SST (d) in toluene solution

图7. 3Ph-SPT (a)、Ph2Ad-SPT (b)、Ph2Ad-SDT (c)和Ph2Ad-SST (d)分子的电子(粉)和空穴(白)波函数分布

Figure 7. Distribution of electron (pink) and hole (white) wavefunctions for the molecules 3Ph-SPT (a), Ph2Ad-SPT (b), Ph2Ad-SDT (c), and Ph2Ad-SST (d)

	λ_ISC	λ_RISC	λ_S0-S1	E(S₁)*	E(T₁)*	ΔE_ST*	f	SOC
3Ph-SPT	0.009	0.004	34.803	2.731	2.711	0.020	0.0055	0.082
Ph2Ad-SPT	0.035	0.060	33.388	2.705	2.712	－0.007	0.0056	0.086
Ph2Ad-SDT	0.018	0.007	32.953	2.880	2.817	0.063	0.0051	0.054
Ph2Ad-SST	0.015	0.007	41.489	2.849	2.830	0.019	0.0051	0.132

表3. 所研究分子的激发动力学相关参数(λS1-S0: kJ/mol, SOC: cm−1, 其余均为: eV, *表示绝热能量(基于S1/T1优化结构的能量))

Table 3. Key parameters of excitation dynamics for the investigated molecules (λS1-S0 in kJ/mol, SOC in cm⁻1, and other parameters in eV, * denotes adiabatic energies based on the optimized S1/T1 structures)

	k_ISC/s⁻¹	k_RISC/s⁻¹	k_r/s⁻¹
3Ph-SPT	7.39×10⁶	6.79×10⁶	1.35×10⁶
Ph2Ad-SPT	6.27×10⁶	4.95×10⁶	1.33×10⁶
Ph2Ad-SDT	1.63×10⁵	1.00×10⁴	1.43×10⁶
Ph2Ad-SST	1.74×10⁷	2.10×10⁷	1.30×10⁶

表4. 所研究分子的激发态动力学速率

Table 4. Excited-state dynamics rates of the investigated molecules

图8. Ph2Ad-SST分子在薄膜中的光物理性质. (a) HOMO和LUMO的空间分布和HOMO-LUMO能隙. (b)紫外吸收光谱和荧光发射光谱

Figure 8. Photophysical properties of Ph2Ad-SST molecules in thin film. (a) Spatial distribution of HOMO and LUMO and HOMO-LUMO energy gap. (b) Ultraviolet absorption spectrum and fluorescence emission spectrum

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