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热活化延迟荧光分子取代基位置对发光性质影响的理论研究

作者:文阅期刊网 来源:文阅编辑中心 日期:2022-10-18 08:52人气:
  摘    要:热活化延迟荧光(TADF)材料具有较高的激子利用率,在有机发光二极管(OLED)研究中备受关注。与蓝色和绿色TADF分子相比,红色TADF分子发光能隙窄,其激发态很容易以不发光的非辐射方式失活回到基态,因此,实验上很难获得发光效率较高的红色TADF材料。本文应用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)方法,研究了互为异构体的T-DA-2和C-DA-2分子的电子吸收光谱、延迟荧光性质及光物理过程机制。计算结果表明,T-DA-2和C-DA-2分子的电子吸收谱主要来自基态到较高能级激发态的电子跃迁,并且其荧光发射遵循反-Kasha规则。和C-DA-2相比,异构体T-DA-2因为更小的内转换速率和更有效的反系间窜越过程而具有更好的荧光和延时荧光特性,表现出显著的取代基位置效应。
 
  关键词:热活化延迟荧光;激发态;取代基位置效应;含时密度泛函理论;量子力学/分子力学组合方法;
 
  Theoretical study on the substituent position effect on luminescence properties of the
 
  thermally activated delayed fluorescencemolecule
 
  SHEN Yu ZHANG Qing CAO Zexing
 
  College of Chemistry and Chemical Engineering, Fujian Provincial Key Laboratory of Theoretical
 
  and Computational Chemistry, Xiamen University Department of Materials Engineering, Huzhou
 
  University, Huzhou Key Laboratory of Environmental Functional Materials and Pollution Control
 
  Abstract:Thermally activated delayed fluorescence (TADF) materials have attracted considerable attention in the organic light-emitting diode (OLED) research due to their high exciton efficiency. In comparison with blue and green TADF molecules, red TADF molecules have a relatively narrow luminous energy gap, and their excited states are easy to deactivate back to the ground state through the non-radiative decay. Therefore, it is difficult to obtain red TADF materials with high luminous efficiency experimentally. Herein, the density functional theory (DFT) and the time-dependent density functional theory (TD-DFT) were used to study electronic absorptions, delayed fluorescence properties, and photophysical processes of T-DA-2 and C-DA-2 molecules. The present results show that main electronic absorptions of T-DA-2 and C-DA-2 mainly arise from the electronic excitation from the ground state to high-lying excited states, and their fluorescence emissions follow the anti-Kasha rule. Compared to C-DA-2, the T-DA-2 isomer has better fluorescence and thermally activated delayed fluorescence characteristics due to smaller internal conversion rate and more efficient reverse intersystem crossing process, showing significant substituent position effects.
 
  Keyword:thermally activated delayed fluorescence; excited state; the substituent position effect; time-dependent density functional theory; quantum mechanics/molecular mechanics combined method;
 
  热活化延迟荧光(TADF)材料可以同时利用单重态和三重态激子发光,其最大内量子效率理论上可达100%,且TADF材料通常为不含贵金属的纯有机分子,价格低廉,具有十分广阔的应用前景[1,2,3]。相对于传统的荧光材料,TADF材料可以通过反系间窜越(RISC)过程从最低三重激发态(T1)跃迁至最低单重激发态(S1),然后再以发射延迟荧光的方式释放能量回到基态(S0)。所以,单-叁态之间的能级差(ΔEST)对于TADF分子的延迟荧光性能至关重要。通常,可以通过最小化最低未占据分子轨道(LUMO)和最高占据分子轨道(HOMO)之间的轨道重叠,以获得足够小的ΔEST[4,5,6,7,8,9,10,11,12],来实现有效的RISC过程。
 
  相关研究表明,一些基于蓝色和绿色TADF材料的有机发光二极管(OLED)的外量子效率(EQEs)能达到30%以上[13,14,15,16],具有极大的实际应用价值。然而发光波长超过600 nm的红色TADF材料,由于发光带隙窄,在发光时通常伴随着显著的非辐射跃迁,导致其量子效率(ΦPL)普遍偏低[17,18,19,20,21,22]。因此,研发具有较高ΦPL和较小ΔEST的红色TADF材料仍然面临着巨大的挑战。基于常用的分子设计策略,可以通过构造高度扭曲的电子给体-受体(D-A)框架和/或增强给体和受体基团的刚性实现较小的ΔEST。ΦPL可由以下公式确定[23,24]:
 
  其中,kr是荧光过程的辐射跃迁速率,kIC则是衡量不发光的非辐射跃迁过程的内转换(IC)速率。由式(1)可知,抑制不发光的IC过程,增强发光的辐射跃迁过程,可以有效地提高发光材料的ΦPL。通过构造刚性强的平面稠环结构,可以有效地抑制D-A分子骨架的旋转和振动,继而抑制其非辐射衰减过程。最近,Chen等报道了10-(二苯并[a,c]二吡啶并[3,2-h:2’,3’-j]吩嗪-12-基)-10H-吩恶嗪(BPPZ-PXZ)红色TADF分子,ΦPL高达100%,发射波长为607 nm[25]。Zhang等报道的红色TADF分子11,12-双(4-(二苯胺基)苯基)二苯并[a,c]酚嗪-3,6-二腈(TPA-PZCN)的发射波长为628 nm,ΦPL高达97%[26]。然而,波长大于630 nm的高效红色TADF分子目前鲜有报道,且对分子结构影响荧光发射过程的机制也缺乏充分了解。因此,进一步认识光物理性质与分子结构之间的关系,对于高性能红色TADF分子材料的设计至关重要。
 
  基于Wang等合成的光功能分子的两种异构体T-DA-2和C-DA-2[27](图1),本研究对其延迟荧光性质和发光机理进行了系统的计算模拟研究。其中,菲[4,5-abc]吩嗪-11,12-二甲腈(PPDCN)为电子受体基团,9,9-二苯基吖啶-10(9H)-基(DPAC)为电子给体基团。通过理论计算,本研究预测了其单体分子的吸收光谱、发光性质、辐射跃迁速率、非辐射跃迁速率以及系间窜越(ISC)和RISC速率,探讨了DPAC基团相对位置的变化对T-DA-2和C-DA-2分子光物理过程和TADF性能的影响;此外,还采用ONIOM方法,研究了固态环境对T-DA-2和C-DA-2分子荧光性质的影响。
 
  1计算细节
 
  应用M06泛函和6-31G(d,p)基组[28],优化了T-DA-2和C-DA-2分子的S0、S1/S2/S3和较低三重激发态的几何结构并分析了振动频率,所有态平衡结构的谐振动频率都是正值,均为势能面上的稳定结构。基于S0和S1态的优化几何构型,采用结合极化连续介质模型(PCM)的TD-M06方法,分别模拟了T-DA-2和C-DA-2分子在甲苯溶液中的紫外-可见吸收光谱和荧光发射性质。所有密度泛函理论(DFT)[29]和含时密度泛函理论(TD-DFT)[30]计算均在Gaussian 16软件中完成[31]。
 
  根据爱因斯坦自发辐射方程,分别估算了T-DA-2和C-DA-2分子在荧光发射过程中的辐射跃迁速率kr。采用MOMAP程序包[32,33]定量地估算了S1→S0的内转换速率kic,并结合ADF 2016软件包[33]计算的单重激发态和三重激发态之间的自旋轨道耦合(SOC)常数(⟨Sn|ĤSOC|Tn⟩),定量地估算了单-叁态之间的ISC速率(kISC)和RISC速率(kRISC)。此外,采用Multiwfn程序包[35]分析了荧光发射过程中电子跃迁的自然轨道(NTOs)分布。
 
  基于两层的ONIOM模型,采用量子力学/分子力学(QM/MM)组合的计算方法[36],研究了固态环境对T-DA-2和C-DA-2分子的发光性质的影响。在QM/MM方法中,QM方法只对中心分子进行结构优化和电子激发研究,而周围的分子作为环境被冻结,并采用低精度的MM方法模拟。此外,还采用静电嵌入[37]的方式模拟了QM区和MM区之间的静电相互作用。基于从实验文献中提取的单晶结构[27],以QM区域的分子为中心,截取其周围1.0 nm以内的所有分子组成团簇,构建了QM/MM计算的初始模型。通过TD-DFT/M06-6-31G(d,p)计算,优化了中心QM分子的几何结构。计算中,采用基于电荷均衡方法(QEQ)计算的原子电荷和通用的力场(UFF)[38],对MM环境分子进行了模拟。
 
  2结果与讨论
 
  2.1电子吸收光谱
 
  基于优化的S0态几何构型,采用TD-M06泛函并结合PCM溶剂模型,分别模拟了T-DA-2和C-DA-2分子在甲苯溶液中的紫外-可见吸收光谱,如图2所示。通过比较实验[27]和理论光谱可以看出,在300∼500 nm的波长范围内,理论模拟的T-DA-2和C-DA-2的两个主要吸收峰的相对位置和具体的出峰位置都可以很好地重现实验观测峰,说明了TD-M06/6-31G(d,p)方法可以合理预测T-DA-2和C-DA-2分子的激发态性质。
 
  计算表明,T-DA-2分别在331和478 nm处有两个明显的吸收峰,其在478 nm处的最大吸收峰源于S0→S6态的电子跃迁。和T-DA-2分子类似,C-DA-2分子分别在342和455 nm处有两个吸收峰,并且其在455 nm处的最大吸收峰来自S0→S8态的电子跃迁。此外,T-DA-2分子和C-DA-2分子的S0→S1态跃迁的振子强度接近于零,对于光吸收过程的贡献很小,由此可以推测这两个分子的S1态可能具有较低的光学活性。
 
  2.2荧光发射性质
 
  基于优化的低能级激发态(S1、S2和S3)的几何构型(图3),采用TD-M06泛函并结合PCM溶剂模型,研究了T-DA-2和C-DA-2在甲苯溶液中的荧光发射。考虑到计算方法对荧光发射性质的影响,分别采用M06、PBE0、MPW1B95、MN15和BMK等具有不同Hartree-Fock成分的杂化泛函,计算模拟了T-DA-2和C-DA-2在甲苯溶液中的荧光发射,相应的垂直发射波长(λem)和振子强度(f)列于表1,实验测得的T-DA-2和C-DA-2在甲苯溶液中的荧光发射峰分别为638和726 nm[27]。根据Kasha规则[39],在光化学中的发光态通常都为S1态,然而,如表1所示,上述泛函计算预测的T-DA-2和C-DA-2的S1态的振子强度几乎都接近于零,说明它们S1态很有可能都是荧光暗态。
 
  表1结果表明,实验检测到T-DA-2和C-DA-2在甲苯溶液中的荧光发射,很有可能来自较高能级的单重激发态而非S1态,即遵循反-Kasha规则[40,41,42,43]。注意到,理论模拟的T-DA-2和C-DA-2分子的荧光发射波长和泛函的选择密切相关,很难有一种泛函可以同时准确预估T-DA-2和C-DA-2分子的荧光发射波长。可以推测,由于这些分子的荧光发射受溶剂影响显著,在不同极性溶剂中其发射波长波动性较大,TD-DFT方法结合隐式连续介质模型不能很好地模拟T-DA-2和C-DA-2分子的荧光发射激发态的性质。与荧光发射相比,吸收光谱则几乎不受溶剂影响,而TD-M06泛函则可以很好地重现T-DA-2和C-DA-2分子的吸收谱图(图2),因此本文最终选择了M06泛函定性地模拟T-DA-2和C-DA-2分子的电子结构和激发性能。
 
  TD-M06方法预测的T-DA-2分子的S2态的振子强度为0.2703,比其相应的S1态的振子强度(f = 0.0002)明显大很多,相应的发射波长为551 nm。对于C-DA-2分子,TD-M06方法预测的S1和S2态的振子强度几乎都为零,然而其S3态的振子强度为0.2042,相应的发射波长为466 nm。进一步分析发现,T-DA-2和C-DA-2的S1态的跃迁偶极矩分别只有0.19和0.25 D,然而T-DA-2的S3态和C-DA-2的S2态的跃迁偶极矩却分别高达5.63和4.75 D。由此我们推测,尽管计算预测S1态的荧光发射和实验观测到的光致发光能区更接近,由于其缺乏光物理活性,T-DA-2和C-DA-2异构体的荧光发射更有可能分别源自其较高能级激发态S2和S3的直接辐射,表现出反-Kasha特征。同时DPAC给电子基团位置的变化,可以显著影响T-DA-2和C-DA-2异构体的荧光发射态以及相应的激发态光物理性质。
 
  2.3延迟荧光光物理过程
 
  如图4所示,基于T-DA-2和C-DA-2分子优化的S1和S2/S3态构型,分别绘制了分子的S1→S0和S2/S3→ S0的NTOs分布图,并标注了相应激发态的跃迁能、振子强度,以及电荷转移跃迁(CT)所占的百分比。对于T-DA-2和C-TD-2分子,所列激发态的空穴主要位于DPAC基团中3个苯环组成的π平面上,而电子主要分布在PPDCN基团的π平面上,表现出显著的电荷转移特征。进一步分析发现,T-DA-2和C-TD-2分子的S1态和S2/S3态跃迁至S0态时的电荷转移比例都高达93%以上,说明从激发态跃迁至S0态时电荷分布的重叠程度很低,两个分子的单-叁态能级差较小。
 
  为了进一步判断T-DA-2和C-DA-2分子的荧光发射态和失活途径,分别模拟了T-DA-2和C-DA-2分子的S1→S0的kr和kIC、T-DA-2分子的S2→S0态和C-DA-2分子的S3→S0态的kr和kIC,以及它们相应的kISC和kRISC等光物理过程的速率。计算结果表明,T-DA-2和C-DA-2分子的S1→S0的kr为4.02×104和2.60×104 s-1,然而这两种分子的S1→S0的kIC分别高达9.03×109和6.06×1010 s-1,远远大于分子的kr。此外,T-DA-2和C-DA-2的S1态到与其能量最接近的T1态的kISC分别只有3.84×104和5.25×106 s-1,远低于它们相应的kIC。由此推测,T-DA-2和C-DA-2的S1态的能量主要以不发光的内转换方式失活。
 
  随后又分析了T-DA-2和C-DA-2分子较高能级的S2/S3态的光物理过程。虽然T-DA-2和C-DA-2分子的S2/S3→S0的kic也分别达到了1.30×1010和4.03×1010 s-1,然而T-DA-2分子S2→S0的kr为9.74×107 s-1,C-DA-2分子S3→S0的kr为1.06×108 s-1,相对于S1态,T-DA-2和C-DA-2的较高能级激发态可以发生更有效的辐射跃迁。进一步分析发现,T-DA-2相应的S2→S0的寿命为10.26 ns,C-DA-2的S3→S0的寿命为9.40 ns。综上所述,相对于S1态,T-DA-2分子的S2态和C-DA-2分子的S3态更有可能是荧光态,即这两个分子的荧光发射遵循反-Kasha规则。
 
  由于T-DA-2的S2态和C-DA-2分子的S3态都分别与其对应T4态的能级最接近,相应的能差分别为0.02和0.21 eV(表2),所以首先考虑T-DA-2分子的S2和T4态以及C-DA-2分子的S3和T4态之间的ISC和RISC过程。基于MOMAP程序估算的T-DA-2分子S2和T4态之间的kISC和kRISC均为5.29×105 s-1,明显小于其S2→S0的kr(9.74×107 s-1)和kIC(1.30×1010 s-1),说明T-DA-2分子S2和T4态之间无法发生有效的ISC和RISC过程。进一步分析发现,T-DA-2分子的S2和T5态之间的能差为0.19 eV,虽然比S2和T4态之间的能差(0.02 eV)大,但其旋轨耦合常数⟨S2|ĤSOC|T5⟩为0.35 cm-1,明显大于⟨S2|ĤSOC|T4⟩的值0.12 cm-1,也大于⟨S2|ĤSOC|T6⟩(0.13 cm-1)以及⟨S2|ĤSOC|T7⟩的值(0.17 cm-1)(表2),建议T-DA-2的S2和T5态之间可能具有更加有效的ISC和RISC过程。基于MOMAP程序估算的T-DA-2分子S2和T5态之间的kISC和kRISC均为4.50×106 s-1,明显大于其S2和T4态之间的kISC和kRISC(5.29×105 s-1),并且该值与T-DA-2分子的S2→S0的kr相当(9.74×107 s-1),说明T-DA-2分子的S2和T5可以发生有效的ISC和RISC过程,继而发射延迟荧光。理论估算的C-DA-2分子的S3态和T4态之间的kISC和kRISC分别为5.62×107和1.35×106 s-1,而其S3和T5态之间kISC和kRISC分别为3.55×106和8.36×104 s-1,说明C-DA-2分子的S3和T4态之间具有更加有效的ISC和RISC过程。进一步分析发现,C-DA-2分子的S3和T4态之间的kISC(5.62×107 s-1)和kRISC(1.35×106 s-1)与其S3→S0的kr(1.06×108 s-1)相差不多,说明C-DA-2也可以发生有效的ISC和RISC过程,继而发射延迟荧光。
 
  虽然C-DA-2的S3→T4的kISC(5.62×107 s-1)比T-DA-2的S2→T5(4.50×106 s-1)大一个数量级,然而T-DA-2的T5→S2的kRISC(4.50×106 s-1)却比C-DA-2的T4→S3的krisc(1.35×106 s-1)大,说明T-DA-2具有更加有效的RISC过程。上述理论模拟的NTOs分布图、单-叁态能级差、以及光物理过程的速率,合理地解释了T-DA-2和C-DA-2具有的延迟荧光性能,同时T-DA-2分子因为具有更加有效的RISC过程而具有更好的延迟荧光性能。T-DA-2和C-DA-2分子的延迟荧光光物理过程机制如图5所示。
 
  2.4 固态环境中的荧光发射
 
  为了研究固态环境对发光性质的影响,本研究分别构建了T-DA-2和C-DA-2分子在固态环境中的两层ONIOM计算模型,ONIOM模型中的QM和MM分区如图6所示。采用TD-M06/MM方法和6-31G(d,p)基组,分别模拟了T-DA-2和C-DA-2分子在固态环境中的吸收光谱和荧光发射,表3给出了相应的主要谱峰位置和荧光发射的振子强度。计算结果表明,在固态和溶液环境中,T-DA-2分子和C-DA-2分子的荧光发射过程一致,在实验上观测到的发射峰分别为S2→S0和S3→S0的荧光发射。由于在ONIOM模型中优化高能级三重态比较困难,因此基于基态的几何构型,计算预测,T-DA-2和C-DA-2异构体的单-叁态垂直激发能差分别为0.03和0.04 eV,均较小,说明ISC和RISC过程可以发生。
 
  为了评估基态和相关激发态几何构型之间的整体差异,基于均方根位移(RMSD)值,比较了T-DA-2和C-DA-2分子在甲苯溶液和固态环境中基态与荧光发射态的几何构型变化。如图7所示,在甲苯溶液中,T-DA-2分子和C-DA-2分子的S0 vs S2和S0 vs S3的RMSD值为分别为0.103和1.247 Å。和T-DA-2分子相比,C-DA-2分子的荧光发射态的几何构型发生了明显的变化。从图7中结构对比可以看出,C-DA-2分子的S0 vs S3较大的构型差异主要源于DPAC基团中的一个苯环发生了明显的扭转,这种结构弛豫导致了C-DA-2(4.03×1010 s-1)具有比T-DA-2(1.3×1010 s-1)更大的kic。在固态环境中,T-DA-2和C-DA-2分子的S0 vs S2的RMSD值分别为0.018 和0.024 Å,明显小于甲苯溶液中的构型变化,说明在固态环境中分子的聚集可以有效地抑制T-DA-2和C-DA-2分子激发态的结构弛豫,减小非辐射跃迁的速率,有助于提高其荧光发光效率。
 
  3 结 论
 
  本文采用DFT和TD-DFT计算方法,系统地研究了T-DA-2和C-DA-2分子的电子吸收光谱、荧光发射性质及延迟荧光光物理过程。计算表明,T-DA-2和C-DA-2分子在478 和455 nm处的最大吸收峰分别源自S0态到较高能级激发态的电子跃迁,说明高能级激发态可能具有更高的光物理活性。在溶液和固态环境中,T-DA-2和C-DA-2分子的荧光发射态分别为S2和S3,均遵循反-Kasha规则。在溶液环境中,和C-DA-2相比,理论预估的T-DA-2因为具有更加有效的RISC过程和更小的kic而具有更好的延迟荧光性能。此外,固态环境中分子的聚集可以有效地抑制T-DA-2和C-DA-2分子激发态的结构弛豫,提高其发光效率。计算结果也揭示,DPAC给电子基团位置的变化,使T-DA-2在荧光发射时具有更小的构型弛豫和更有效的RISC过程,继而可以显著影响异构体T-DA-2和C-DA-2的荧光和延迟荧光性质。
 
  参考文献
 
  [1] UOYAMA H, GOUSHI K, SHIZU K, et al. Highly efficient organic light-emitting diodes from delayed fluorescence[J]. Nature, 2012, 492(7428): 234-238.
 
  [2] HIRATA S, SAKAI Y, MASUI K, et al. Highly efficient blue electroluminescence based on thermally activated delayed fluorescence[J]. Nature materials, 2015, 14(3): 330-336.
 
  [3] RAJAMALLI P, SENTHILKUMAR N, GANDEEPAN P, et al. A new molecular design based on thermally activated delayed fluorescence for highly efficient organic light emitting diodes[J]. Journal of the American Chemical Society, 2016, 138(2): 628-634.
 
  [4] KAJI H, SUZUKI H, FUKUSHIMA T, et al. Purely organic electroluminescent material realizing 100% conversion from electricity to light[J]. Nature communications, 2015, 6(1): 1-8.
 
  [5] KAWASUMI K, WU T, ZHU T, et al. Thermally activated delayed fluorescence materials based on homoconjugation effect of donor–acceptor triptycenes[J]. Journal of the American Chemical Society, 2015, 137(37): 11908-11911.
 
  [6] ZHANG J, DING D, WEI Y, et al. Multiphosphine-oxide hosts for ultralow-voltage-driven true-blue thermally activated delayed fluorescence diodes with external quantum efficiency beyond 20%[J]. Advanced Materials, 2016, 28(3): 479-485.
 
  [7] OBOLDA A, PENG Q, HE C, et al. Triplet-polaron-interaction-induced upconversion from triplet to singlet: a possible way to obtain highly efficient OLEDs[J]. Advanced Materials, 2016, 28(23): 4740-4746.
 
  [8] LIU W, CHEN J X, ZHENG C J, et al. Novel strategy to develop exciplex emitters for high-performance OLEDs by employing thermally activated delayed fluorescence materials[J]. Advanced Functional Materials, 2016, 26(12): 2002-2008.
 
  [9] DATA P, PANDER P, OKAZAKI M, et al. Dibenzo [a, j] phenazine-cored donor-acceptor-donor compounds as green-to-red/NIR thermally activated delayed fluorescence organic light emitters[J]. Angewandte Chemie, 2016, 128(19): 5833-5838.
 
  [10] WONG M Y, ZYSMAN-COLMAN E. Purely organic thermally activated delayed fluorescence materials for organic light-emitting diodes[J]. Advanced Materials, 2017, 29(22): 1605444.
 
  [11] ETHERINGTON M K, FRANCHELLO F, GIBSON J, et al. Regio-and conformational isomerization critical to design of efficient thermally-activated delayed fluorescence emitters[J]. Nature communications, 2017, 8(1): 1-11.
 
  [12] ZHANG D, QIAO J, ZHANG D, et al. Ultrahigh-efficiency green PHOLEDs with a voltage under 3 V and a power efficiency of nearly 110 lm W<sup>-1</sup> at luminance of 10000 cd m<sup>-2</sup>[J]. Advanced Materials, 2017, 29(40): 1702847.
 
  [13] LIN T A, CHATTERJEE T, TSAI W L, et al. Sky‐blue organic light emitting diode with 37% external quantum efficiency using thermally activated delayed fluorescence from spiroacridine-triazine hybrid[J]. Advanced Materials, 2016, 28(32): 6976-6983.
 
  [14] AHN D H, KIM S W, LEE H, et al. Highly efficient blue thermally activated delayed fluorescence emitters based on symmetrical and rigid oxygen-bridged boron acceptors[J]. Nature Photonics, 2019, 13(8): 540-546.
 
  [15] KONDO Y, YOSHIURA K, KITERA S, et al. Narrowband deep-blue organic light-emitting diode featuring an organoboron-based emitter[J]. Nature Photonics, 2019, 13(10): 678-682.
 
  [16] WU T L, HUANG M J, LIN C C, et al. Diboron compound-based organic light-emitting diodes with high efficiency and reduced efficiency roll-off[J]. Nature Photonics, 2018, 12(4): 235-240.
 
  [17] ENGLMAN R, JORTNER J. The energy gap law for radiationless transitions in large molecules[J]. Molecular Physics, 1970, 18(2): 145-164.
 
  [18] CASPAR J V, KOBER E M, SULLIVAN B P, et al. Application of the energy gap law to the decay of charge-transfer excited states[J]. Journal of the American Chemical Society, 1982, 104(2): 630-632.
 
  [19] CUMMINGS S D, EISENBERG R. Tuning the excited-state properties of platinum (Ⅱ) diimine dithiolate complexes[J]. Journal of the American Chemical Society, 1996, 118(8): 1949-1960.
 
  [20] WILSON J S, CHAWDHURY N, AL-MANDHARY M R A, et al. The energy gap law for triplet states in Pt-containing conjugated polymers and monomers[J]. Journal of the American Chemical Society, 2001, 123(38): 9412-9417.
 
  [21] ZHANG Q, LI J, SHIZU K, et al. Design of efficient thermally activated delayed fluorescence materials for pure blue organic light emitting diodes[J]. Journal of the American Chemical Society, 2012, 134(36): 14706-14709.
 
  [22] JANKUS V, DATA P, GRAVES D, et al. Highly efficient TADF OLEDs: how the emitter–host interaction controls both the excited state species and electrical properties of the devices to achieve near 100% triplet harvesting and high efficiency[J]. Advanced Functional Materials, 2014, 24(39): 6178-6186.
 
  [23] ZHANG Q, LI B, HUANG S, et al. Efficient blue organic light-emitting diodes employing thermally activated delayed fluorescence[J]. Nature photonics, 2014, 8(4): 326-332.
 
  [24] ZHANG Q, KUWABARA H, POTSCAVAGE JR W J, et al. Anthraquinone-based intramolecular charge-transfer compounds: computational molecular design, thermally activated delayed fluorescence, and highly efficient red electroluminescence[J]. Journal of the American Chemical Society, 2014, 136(52): 18070-18081.
 
  [25] CHEN J X, TAO W W, CHEN W C, et al. Red/near-infrared thermally activated delayed fluorescence OLEDs with near 100% internal quantum efficiency[J]. Angewandte Chemie, 2019, 131(41): 14802-14807.
 
  [26] ZHANG Y L, RAN Q, WANG Q, et al. High-efficiency red organic light-emitting diodes with external quantum efficiency close to 30% based on a novel thermally activated delayed fluorescence emitter[J]. Advanced Materials, 2019, 31(42): 1902368.
 
  [27] YANG T , CHENG Z , LI Z , et al. Improving the efficiency of red thermally activated delayed fluorescence organic light-emitting diode by rational isomer engineering[J]. Advanced Functional Materials, 2020:2002681.
 
  [28] ZHAO Y, TRUHLAR D G. The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals[J]. Theoretical chemistry accounts, 2008, 120(1): 215-241.
 
  [29] PARR R G. Density functional theory of atoms and molecules[M]//Horizons of quantum chemistry. Springer, Dordrecht, 1980: 5-15.
 
  [30] RUNGE E, GROSS E K U. Density-functional theory for time-dependent systems[J]. Physical Review Letters, 1984, 52(12): 997.
 
  [31] FRISCH M J, TRUCKS G W, SCHLEGEL H B, et al. Gaussian 16 Revision C. 01, 2016[CP]. Gaussian Inc. Wallingford CT, 2016.
 
  [32] NIU Y, PENG Q, DENG C, et al. Theory of excited state decays and optical spectra: Application to polyatomic molecules[J]. The Journal of Physical Chemistry A, 2010, 114(30): 7817-7831.
 
  [33] Shuai Z, Peng Q, Niu Y, MOMAP, Revision 2020A (2.2.0), Tsinghua University, Beijing, China, 2014.
 
  [34] TE VELDE G, BICKELHAUPT F M, BAERENDS E J, et al. Chemistry with ADF[J]. Journal of Computational Chemistry, 2001, 22(9): 931-967.
 
  [35] LU T, CHEN F. Multiwfn: a multifunctional wavefunction analyzer[J]. Journal of Computational Chemistry, 2012, 33(5): 580-592.
 
  [36] CHUNG L W, SAMEERA W M C, RAMOZZI R, et al. The ONIOM method and its applications[J]. Chemical Reviews, 2015, 115(12): 5678-5796.
 
  [37] VREVEN T, BYUN K S, KOMÁROMI I, et al. Combining quantum mechanics methods with molecular mechanics methods in ONIOM[J]. Journal of Chemical Theory and Computation, 2006, 2(3): 815-826.
 
  [38] RAPPÉ A K, CASEWIT C J, COLWELL K S, et al. UFF, a full periodic table force field for molecular mechanics and molecular dynamics simulations[J]. Journal of the American chemical society, 1992, 114(25): 10024-10035.
 
  [39] KASHA M. Characterization of electronic transitions in complex molecules[J]. Discussions of the Faraday society, 1950, 9: 14-19.
 
  [40] QIAN E A, WIXTROM A I, AXTELL J C, et al. Atomically precise organomimetic cluster nanomolecules assembled via perfluoroaryl-thiol SN Ar chemistry[J]. Nature chemistry, 2017, 9(4): 333-340.
 
  [41] PENG Z, WANG Z, HUANG Z, et al. Expression of anti-Kasha’s emission from amino benzothiadiazole and its utilization for fluorescent chemosensors and organic light emitting materials[J]. Journal of Materials Chemistry C, 2018, 6(29): 7864-7873.
 
  [42] DEMCHENKO A P, TOMIN V I, CHOU P T. Breaking the Kasha rule for more efficient photochemistry[J]. Chemical reviews, 2017, 117(21): 13353-13381.
 
  [43] SCUPPA S, ORIAN L, DONOLI A, et al. Anti-Kasha’s rule fluorescence emission in (2-ferrocenyl) indene generated by a twisted intramolecular charge-transfer (TICT) process[J]. The Journal of Physical Chemistry A, 2011, 115(30): 8344-8349.
 
  [44] ENGLMAN R, JORTNER J. The energy gap law for radiationless transitions in large molecules[J]. Molecular Physics, 1970, 18(2): 145-164.
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