Excited state characters and components play a decisive role in photoluminescence (PL) and electroluminescence (EL) properties of organic light‐emitting materials (OLEDS). Charge‐transfer (CT) state is beneficial to enhance the singlet exciton utilizations in fluorescent OLEDs by an activated reverse intersystem crossing process, due to the minimized singlet and triplet energy splitting in CT excitons. However, the dominant CT component in the emissive state significantly reduces the PL efficiency in such materials. Here, the strategy is to carry out a fine excited state modulation, aiming to reach a golden combination of the high PL efficiency locally emissive (LE) component and the high exciton utilizing CT component in one excited state. As a result, a quasi‐equivalent hybridization of LE and CT components is obtained in the emissive state upon the addition of only an extra phenyl ring in the newly synthesized material 4‐[2‐(4′‐diphenylamino‐biphenyl‐4‐yl)‐phenanthro[9,10‐d]imidazol‐1‐yl]‐benzonitrile (TBPMCN), and the nondoped OLED of TBPMCN exhibited a record‐setting performance: a pure blue emission with a Commission Internationale de L'Eclairage coordinate of (0.16, 0.16), a high external quantum efficiency of 7.8%, and a high yield of singlet exciton of 97% without delayed fluorescence phenomenon. The excited state modulation could be a practical way to design low‐cost, high‐efficiency fluorescent OLED materials.

Herein, a simple aza-aromatic compound dibenzo[a,c]phenazine (DPPZ), which exhibits single-molecule white light with a ternary emission, consisting of simultaneous fluorescence (S 1 →S 0 ) and dual room-temperature phosphorescence (RTP, T 2 →S 0 and T 1 →S 0 ) is reported. The Commission Internationale de l' Éclairage coordinates of DPPZ powder are (0.28, 0.33). To everyone's knowledge, this is the first case to achieve single-molecule white emission with ternary emission of fluorescence and dual RTP. This finding provides a prototype strategy to realize low-cost, stable pure organic singlemolecule white light emission with three standard primary colors through further precise modulation of excited states.

A greatly enhanced proportion of radiative excitons in non-doped blue electroluminescence with a maximum exciton utilizing efficiency (EUE) of 85% is harvested in the orthogonal cyano substituted, charge transfer (CT) emitter TPMCN, in comparison to the localized emission (LE)-like emitter TPM with a low EUE of 16%.

The excited state properties of organic fluorescent materials are crucial for their photoelectronic performance. Here, a study on the highly efficient electrofluorescent material 4(2(4′(diphenylamino)[1,1′biphenyl]4yl)1H phenanthro[9,10d]imidazol1yl)benzonitrile (TBPMCN) is carried out, focusing mainly on its crystal structure and photophysical properties under pressure stimulation. The special triangularcone (TC) configuration of triphenylamine group in TBPMCN crystal exhibits chargetransfer (CT)dominated excited state property in TBPMCN, which gives rise to a blueshifted emission in the crystal. Theoretical calculations prove that the TC conformation is a dynamically metastable state, which is higher in energy than the threebladepropeller (TBP) configuration. In a further piezochromic experiment, a unique rehybridization induced emission enhancement phenomenon is found in this crystal, which is essentially different from the aggregationinduced emission enhancement (AIEE) mechanism. It can be assigned to the change of excited state property from a CTdominated state to a hybridized locally excited and chargetransfer state, as a result of the rehybridization of nitrogen atom upon the increased external pressure. This work provides deep insight into the relationship between molecular structure and excited state properties in crystal by means of the pres sure stimulation and further enriches the AIEE mechanism. Additionally, the large redshifted piezochromic phenomenon of this CT material is stressed.

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