The insight into understanding the effect of acceptor moieties with phenoxazine (PXD) donor and bridging phenyl (Ph) spacer on structural and electronic properties of excited state was theoretically investigated through density functional theory simulations. Di-phenyltriazine (DPhTRZ), di-phenyl pyrimidine (DPhPyM), and di-pyridyl pyrimidine (DPyPyM) were chosen as acceptor moieties for thermally activated delayed fluorescence (TADF) emitters. It was found that planar structure between phenyl spacer and DPhTRZ/DPyPyM was dominantly determined by intramolecular H-bonds at inner side of acceptor moiety. Depending on the acceptor moieties, the adiabatic excitation energy in singlet and triplet state is shifted to higher energies in order: DPyPyM (blue) > DPhPyM (greenish-blue) > DPhTRZ (green). In the perspective of spin conversion, the exact spin flip barrier, defined as total energy barrier for triplet-to-singlet transition, is in order of DPhTRZ < DPyPyM < DPhPyM. The calculated spin-orbit coupling matrix element with DPyPyM is relatively larger than that with DPhTRZ and DPhPyM. The calculated reverse intersystem crossing rate for triplet conversion is the largest with DPhTRZ and the smallest with DPhPyM. The comprehensive analyses conclusively suggest that DPyPyM acceptor moiety can be utilized for blue TADF emitters with superb structural rigidity, large spin conversion rate and low spin flip barrier.

通过密度泛函理论模拟，从理论上深入了解了理解吩恶嗪（PXD）供体和桥联苯基（Ph）间隔基对受体部分的影响对结构和电子性能的影响。选择二苯基三嗪（DPhTRZ），二苯基嘧啶（DPhPyM）和二吡啶嘧啶（DPyPyM）作为热激活延迟荧光（TADF）发射体的受体部分。发现苯基间隔基与DPhTRZ / DPyPyM之间的平面结构由受体部分内侧的分子内氢键决定。根据受体部分，单重态和三重态的绝热激发能按以下顺序转移到更高的能量：DPyPyM（蓝色）> DPhPyM（绿蓝色）> DPhTRZ（绿色）。从自旋转换的角度来看，精确的自旋翻转势垒定义为DPhTRZ < DPyPyM < DPhPyM。使用DPyPyM计算出的自旋轨道耦合矩阵元素要比使用DPhTRZ和DPhPyM计算出的自旋轨道耦合矩阵元素相对更大。对于DPhTRZ，计算出的三重态转换的反向系统间交叉速率最大，而对于DPhPyM，最小。综合分析最终表明，DPyPyM受体部分可用于具有出色的结构刚度，大的自旋转化率和低的自旋翻转势垒的蓝色TADF发射体。