# Highly Efficient Blue Host Compound Based on an Anthracene Moiety for OLEDs
## 3 Results and Discussion  
### Molecular Design, Synthesis, and Optical Properties  
Scheme 1 illustrates the synthetic routes of the synthesized 2 NaAn-1-PNa. The final product was synthesized through borylation, bromination, and Suzuki coupling and purified by silica column chromatography or the reprecipitation method. The synthesized compounds were structurally confirmed by nuclear magnetic resonance, elemental analysis, and mass spectrometry (Figures S1-S3). The synthesized 2 NaAn-1-PNa possesses an anthracene core chromophore with aryl groups and an asymmetric structure (Figure 1). The photophysical properties of the synthesized compound were investigated by UV-Visible absorption (UV-Vis) and photoluminescence spectra in toluene solution (10\({}^{-5}\) M)  
Figure 1: Chemical structure of the 2-NaAn-1-PNa. and film states, as shown in Table 1 and Figure 2. In the solution state, 2-NaAn-1-PNa exhibited UV-Vis peaks at 340, 359, 376, and 397 nm, with a maximum photoluminescence (PLmax) at 428 nm. The peaks at 359, 376, and 397 nm corresponded to characteristic vibration peaks of the anthracene molecule. In the vacuum-deposited film, the UV-Vis peaks of the compound were observed at 363, 383, and 403 nm, with a PLmax at 440 nm. From the solution state to the film state, the PLmax exhibited a red shift of approximately 12 nm, likely due to \(\pi\)-\(\pi\)* interactions between molecules in the film. The full-width half maximum (FWHM) values of 2-NaAn-1-PNa were 53 nm in the solution state and 56 nm in the film state. The MNAn compound previously reported by by [PERSON] et al. had a twisted angle of 79.77\({}^{\circ}\) between the 2-naphthyl group and anthracene [24]. In the solution state, the torsion angle between anthracene and the naphthyl group is expected to exhibit a highly twisted structure similar to the values predicted by molecular calculations. However, in the film state, it is anticipated that a moderately twisted structure will be maintained to ensure stability. The highly twisted molecular structure between the core group and side group hinders intermolecular interactions, resulting in relatively narrow FWHM values even in the film state compared to those in the solution state. Moreover, preventing intermolecular interactions results in a non-planar structure that reduces self-aggregation, thereby inhibiting re-crystallization and forming morphologically stable films in OLED devices [25]. The photoluminescence quantum yield (PLQY) of 2-NaAn-1-PNa was 73.1% in the solution state and 30.2% in the film state. The fluorescence lifetime of 2-NaAn-1-PNa was 2.99 ns, and the transient PL spectrum is shown in Figure S4. 2-NaAn-1-PNa exhibited a \(k_{md}\) of 2.44 \(\times\) 10\({}^{8}\)/s and a \(k_{mr}\) of 9.04 \(\times\) 10\({}^{7}\)/s. Therefore, the \(k_{md}\)/\(k_{mr}\) value for 2-NaAn-1-PNa was 2.69 (Table S1). To confirm the potential of 2-NaAn-1-PNa as a blue host, the PL spectrum of 2-NaAn-1-PNa in the film state was observed to overlap with the absorption spectrum of the previously reported 3 Me-1 Bu-TPPDA in the solution state (Figure 3). In the doped device fabricated via evaporated system, the EML consists of 2-NaAn-1-PNa: 4 wt% 3 Me-1 Bu-TPPDA. Therefore, when the host, comprising 96 wt%, emits similarly to its film state in PL, the emitted energy is absorbed by the dopant, 3 Me-1 Bu-TPPDA. Given the low wt% of the dopant compared to the host, the environment resembles that