Deep-blue electroluminescence from nondoped and doped organic light-emitting diodes (OLEDs) based on a new monoaza[6]helicene

• Published in: RSC advances 2015-01, Vol.5 (1), p.75-84
• Main Authors: Hua, Wanming, Liu, Zhi, Duan, Lian, Dong, Guifang, Qiu, Yong, Zhang, Baojie, Cui, Deliang, Tao, Xutang, Cheng, Na, Liu, Yongjun
• Format: Article
• Language: English
• Subjects: Brightness; Efficiency; Electroluminescence; Emitters; Energy measurement; Molecular orbitals; Organic light emitting diodes
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C4RA13486A

A new organic electroluminescent material, monoaza[6]helicene ( 1 ), was successfully prepared via an effective photochemical reaction in about 10 minutes with high productivity. The thermal, photophysical, electrochemical properties, quantum chemical and X-ray structural studies as well as characteristics of organic light-emitting diodes were fully investigated. 1 exhibited excellent solubility and high thermal stability. The first singlet excitation energy of 1 was measured to be around 2.92 eV with a HOMO level of −5.19 eV and a LUMO level of −2.27 eV. Helical molecular geometry of 1 effectively blocked the π-conjugation and decreased the close-packing of molecules. Both the nondoped and doped OLEDs emitted deep-blue light at 444 and 462 nm with CIE coordinates of (0.15, 0.09) and (0.15, 0.10). The doped OLED based on 1 was the first example of helicenes as light emitters that exhibited a brightness of more than 3000 cd m −2 with high color purity and excellent efficiency stability.