[11a-A33-1~13] 12.2 Characterization and Materials Physics

11:45 AM - 12:00 PM JST(2:45 AM - 3:00 AM UTC)

[11a-A33-11] Direct determination of electron affinities of OLED materials using low energy inverse photoelectron spectroscopy (LEIPS)

〇Kiyoshi Torizuka¹, Ota Nagaoka¹, Kazuki Nakano¹, Hiroyuki Yoshida^1,2 (1.Chiba Univ., 2.MCRC Chiba Univ)

Keywords:

organic EL material,low energy inverse photoelectron spectroscopy (LEIPS),electron affinity

We accurately determined the electron affinities (EAs) of 18 organic light-emitting diode (OLED) materials using low energy inverse photoelectron spectroscopy (LEIPS). Clear differences in energy levels were observed depending on the material's application, i.e., electron transport material, hole transport material, and host material. From the measured EAs together with literature values for ionization energies and optical gaps, we evaluated the exciton binding energies and band gaps. The exciton binding energies of all 18 materials were approximately 1 eV, which is thought to be close to about 1/4 of the band gap. This relationship is consistent with our previous findings for organic solar cell materials. These results provide important guidance for OLED design and device performance optimization.