Syntheses and OLED applications of phenanthroimidazole-based materials

Date

2024-9-02

Author

İlter, Selin

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OLED devices are on the rise since they are economical, flexible on various polymeric substrates, very thin, and efficient. The devices that use OLED technology include mobile phones, smart watches, computers, and televisions. Emitting material in OLED technology can be either polymers or small molecules, with the condition of possessing a π-conjugated system in their structures. This π-conjugated system supplies electron delocalization in the molecule, which results in being a semiconductor. In this study, phenanthroimidazole derivative small molecules were synthesized by using Debus–Radziszewski and Suzuki cross-coupling reactions. Triphenylamine moiety was added to SM3, SM4, and SM5 molecules to introduce hybridized locally excited and charge transfer state-type emission to these molecules. The effect of electron-withdrawing group substitution on phenanthroimidazole derivatives was investigated with SM2, SM4, SM5, and SM6 molecules. Characterizations of small molecules were conducted by using NMR and HRMS methods. The optical properties of small molecules were investigated by using UV visible and photoluminescence spectroscopies. It was revealed that these molecules (from SM1 to SM6), emit light in the blue region of the visible part of the electromagnetic spectrum after photoexcitation. Electrochemical studies for these materials were done by cyclic voltammetry method. Solvatochromic experiments were carried out for these molecules to examine their excited state properties. Theoretical calculations were performed to decide on the emission mechanisms of these molecules when an external voltage is applied to these molecules. OLED applications for phenanthroimidazole derivatives were conducted. For SM3, SM4, and SM5 molecules, the device configuration of ITO/PEDOT:PSS/NPB/TCTA/Emitter/TPBi/LiF/Al was constructed. For SM1,SM2, and SM6 molecules, the device configuration of ITO/NPB/Emitter/TPBi/LiF/Al was constructed. SM5 had the best OLED performance with a maximum luminance value of 16946 cd.m-2, maximum current efficiency value of 39.70 cd.A-1, turn-on voltage of 3.13V, and CIE color coordinates of (0.15,0.11).

Subject Keywords

Phenanthroimidazole, OLED, Solvatochromic, Triphenylamine, Semiconductor

URI

https://hdl.handle.net/11511/111046

Collections

Graduate School of Natural and Applied Sciences, Thesis