# Highly Efficient Blue Host Compound Based on an Anthracene Moiety for OLEDs
## 3 Results and Discussion
### Molecular Design, Synthesis, and Optical Properties
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Compound**} & \multicolumn{3}{c}{**Solution \({}^{\text{a}}\)**} & \multicolumn{3}{c}{**Film \({}^{\text{b}}\)**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} & \multirow{2}{*}{**HO**} \\  & \(\lambda_{\text{Abs}}\) & \(\lambda_{\text{PT}}\) **(FWHM)** & & & & & \(\lambda_{\text{PL}}\) & & **MO \({}^{\text{c}}\)** & **MO** \\  & **(nm)** & **(nm)** & & & & & **(FWHM)** & **(\%)** & **(eV)** & **(eV)** \\ \hline
2-NaAn-1- & 340, 359, & 428 & 73.1 & 363, 383, & 440 & 440 & 30.2 & \(-\)5.84 & \(-\)2.89 & 3.03/ 2.95 \\ \hline \multirow{4}{*}{PNa} & \multicolumn{3}{c}{\({}^{\text{a}}\) Toluene solution (0.5 wt%), \({}^{\text{b}}\) in thin film state (thickness: 50 nm), \({}^{\text{c}}\) HOMO values derived from ultraviolet photoelectron spectra (Riken-Keiki, AC-2).} & \\  & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Optical properties of the synthesized materials. Figure 2: UV–Vis absorption (left arrow) and PL spectra (right arrow) of anthracene derivatives in (**a**) solution state (toluene, 1 \(\times\) 10\({}^{-5}\) M) and (**b**) film state (thickness: 50 nm). of a solution with very weak intermolecular forces. Therefore, for the dopant, UV-Vis in solution is used to confirm the overlap of the two spectra, ensuring efficient energy transfer from the host to the dopant. Given the proven characteristics of 3 Me-1 Bu-TPPDA as a blue dopant material in our previous research, including high efficiency, real blue emission, and long device lifetime, it was used as the dopant material in this study. The two spectra were sufficiently overlapped, indicating efficient Forster energy transfer from the blue dopant material to 2-NaAn-1 PNa. HOMO levels for both compounds were measured using AC-2, and the LUMO levels were calculated from the HOMO levels and optical band gaps. There are two methods commonly used to calculate the optical band gap: one involves determining the band edge from the absorbance spectrum, and the other utilizes the (_Inv_) versus (_ahv_)\({}^{2}\) plot to identify the absorbance edge [26; 27]. In this paper, the optical band gap was determined by identifying the absorbance edge from the (_Inv_) versus (_ahv_)\({}^{2}\) plot, where \(\alpha\), \(h\), and \(\
u\) denote absorbance, [PERSON]'s constant, and the frequency of light, respectively. The HOMO and LUMO levels of 2-NaAn-1-PNa were \(-\)5.84 eV and \(-\)2.89 eV, with a band gap of 2.95 eV. The HOMO and LUMO levels of the dopant 3 Me-1 Bu-TPPDA used were \(-\)5.84 eV and \(-\)2.89 eV, respectively [22]. The HOMO level was measured using AC-2 equipment. Additionally, the experimental HOMO value was determined using cyclic voltammetry (CV). The HOMO level of 2-NaAn-1-PNa, derived from the oxidation peaks, was found to be \(-\)6.01 eV (Figure S6). The LUMO levels were calculated from the band gap values obtained from the absorbance edge, resulting in a value of \(-\)3.06 eV. Thus, the measurements from CV and AC-2 were consistent. In the solution, the band gap is 3.03 eV, while in the film state it is 2.95 eV, showing a difference of 0.08 eV. Despite their similarity, the band gap is slightly smaller in the film state, a reduction typically attributed to enhanced intermolecular interactions resulting from closer molecular packing. Such interactions influence the electronic structure of the molecules, commonly resulting in a smaller band gap.