Mechanochromic asymmetric sulfone derivatives for use in efficient blue organic light-emitting diodesElectronic supplementary information (ESI) available. CCDC 1490973 and 1490974. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6tc02917e

• Main Authors: Li, Guang, Zhao, Juewen, Zhang, Dan, Shi, Zhichun, Zhu, Zelin, Song, Huanquan, Zhu, Jieji, Tao, Silu, Lu, Feng, Tong, Qingxiao
• Format: Journal Article
• Published: 22.09.2016
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c6tc02917e

Typical π-π stacking is suppressed by the asymmetric molecular design for high fluorescence quantum yield ( Φ f ) blue light emission, overcoming the aggregation caused quenching (ACQ) limitation. In this research, two novel blue fluorescent materials with asymmetric structure: 2-(4′-((4-(9 H -carbazol-9-yl)phenyl)sulfonyl)-[1,1′-biphenyl]-4-yl)-1-(4-( tert -butyl)phenyl)-1 H -phenanthro[9,10- d ]imidazole ( PSC ) and 2-(4′-((4′-(9 H -carbazol-9-yl)-[1,1′-biphenyl]-4-yl)sulfonyl)-[1,1′-biphenyl]-4-yl)-1-(4-( tert -butyl)phenyl)-1 H -phenanthro[9,10- d ]imidazole ( PSBC ), consisting of a sulfone group as the electron acceptor and two different electron donors, carbazole and phenanthroimidazole, were designed and synthesized. The two compounds have high Φ f (95.3% for PSC and 81.1% for PSBC ) in film because of the restricting π-π stacking, and show apparent mechanochromic properties, i.e. , an emission change from deep blue to blue-green resulting from external mechanical stimuli. The emissions display 50 nm/23 nm red shifts after grinding. Organic light emitting diodes (OLEDs) using the two compounds as emitters exhibited good efficiencies: the doped PSC -based device emitted blue light at 444 nm with CIE co-ordinates of (0.151, 0.072). The PSBC -based device also emitted blue light at 444 nm with CIE co-ordinates of (0.151, 0.068). A maximal external quantum efficiency (EQE) of 5.43% was also achieved. Two multifunctional emitters based on asymmetric molecular design overcome the ACQ. The devices showed impressive performance and the emitters showed mechanochromic properties.