Small-size graphene oxide (GO) as a hole injection layer for high-performance green phosphorescent organic light-emitting diodes

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 9; no. 36; pp. 1248 - 12419
• Main Authors: Miao, Yanqin, Yin, Mengna, Wang, Chengqiang, Wei, Xiaozhen, Wang, Zhiyuan, Zhao, Min, Wang, Yiwen, Jia, Zhigang, Wang, Hua, Zhu, Furong
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 28.09.2021
• Subjects: Current efficiency; Efficiency; Graphene; Light emitting diodes; Liquid phases; Organic light emitting diodes; Phosphorescence; Power efficiency; Quantum efficiency; Size distribution; Spin coating; Work functions
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc02898g

In this work, we successfully synthesized small-size GO with the main size distribution at 200-400 nm using the tip sonication-assisted liquid-phase exfoliation method, which shows a suitable work function of 5.16 eV (annealing at 120 °C) well matching the ITO anode (4.80 eV) and extremely high transmittance (>98%, small size GO film spin-coated at 0.75 mg mL −1 GO dispersion). Using small-size GO as hole injection materials, Ir(ppy) 3 -based green phosphorescent organic light-emitting diodes (OLEDs) were demonstrated, and the resulting devices exhibit a lower turn-on voltage of 3.0 V than the PEDOT:PSS-based device (3.3 V). Further, the optimized GO-based OLED achieves maximum current efficiency, power efficiency, and external quantum efficiency reaching 73.14 cd A −1 , 53.95 lm W −1 , and 20.63%, respectively, which are significantly higher than the PEDOT:PSS-based reference device (68.82 cd A −1 , 48.04 lm W −1 , and 19.44%). It was demonstrated that effective holes injection capability and excellent film-forming properties for small-size GO guarantee the achievement of such high device performance. All relevant results indicate that the use of small-size GO as a hole injection material has great potential to alternative PEDOT:PSS in OLEDs. Using small size GO as hole injection materials, the fabricated green OLED with Ir(ppy) 3 as emitter achieves the maximum current efficiency, power efficiency, and EQE reaching 73.14 cd A −1 , 53.95 lm W −1 , and 20.63%, respectively.