Bis(Benzothiophene-S,S-Dioxide) Fused Small Molecules Realize Solution-Processible, High-Performance and Non-Doped Blue Organic Light-Emitting Diodes

The creation of new fluorescent cores plays an important role in developing high-performance blue organic light-emitting diode (OLED) materials. In this study, a series of novel bis(benzothiophene-S,S-dioxide) fused blue emitting molecules (FBTO-EHNa, FBTO-EHSF and FBTO-EHFF), which are symmetrically functionalized by naphthalene, spirobifluorene, 9,9,9’,9’-tetraoctyl-9H,9’H- [2,2’-difluoren], respectively, are designed and synthesized successfully. They possess high thermal stability resulting from the largely fused polycyclic aromatic conformation and polar sulfonyl groups in FBTO unit. Through incorporating the various electron-donating units, the π-conjugation length is effectively controlled, and exhibits the profound influence on the thermal, photophysical and electrochemical properties. Then, these three small molecules are characterized for solution-processible and non-doped OLEDs in details. All of them show the typical blue emission from 456 to 470 nm in the electroluminescent devices. Especially, the FBTO-EHFF is outperformed by both of the FBTO-EHNa and FBTO-EHSF, where it displays a maximum current efficiency (CE) of 6.37 cd A-1 with a CIE coordinates of (0.20, 0.24). These results suggest that rational design on the bis(benzothiophene-S,S-dioxide) fused polycyclic molecules have greatly potential capability for achieving the solution-processible, high-performance and stable blue OLEDs.