Spirally Configured cis-Stilbene/fluorene (STIF), 10,11-Benzo-, and Imidazole-fused STIF Hybrids as Electron-Transporting Materials for Organic Light-Emitting Diode Applications.

A new class of cis-stilbene/fluorene (STIF) and 10,11-benzo- and imidazole-fused dibenzosuberane/fluorene (Bz-STIF and Imd-STIF) spiro hybrid systems with paired cyanophenyl, pyridyl, and/or pyrimidyl units was synthesized as electron transporting materials (ETMs) for blue fluorescent OLEDs (FOLEDs) and phosphorescent organic light emitting diodes (PhOLEDs). Their photophysical (UV-Vis absorption and emission), electrochemical (Eox /Ered ), morphological (glassy transition temperature, Tg ), and thermal stability (decomposition temperature, Td ) properties are systematical compared. Their correlations regarding the effects of the fused unit/substituent(s) in the STIF core on the morphological/thermal stability, HOMO/LUMO energy level, π-electron distribution profiles by DFT calculations, and electron mobility are established. Blue FOLEDs are fabricated by using them and TmPyPB (a control) as ETMs. The effects of their LUMO energy levels and electron mobilities on the device turn-on voltage, performance efficiencies including external quantum efficiency/current efficiency (EQE/CE), power efficiency (PE), and device lifetime at 5% luminescence decay (T95 ) are correlated. Among them, three best ETMs and TmPyPB (a control) are selected for further green and blue PhOLED fabrications. The effects of their LUMO energy levels and electron mobilities on the device turn-on voltage and performance efficiencies are confirmed, allowing for potential commercial applications.

Spirally Configured ( cis-Stilbene) Trimers: Steady-State and Time-Resolved Photophysical Studies and Organic Light-Emitting Diode Applications.

This article reports for the time-resolved photophysical studies of spirally configured ( cis-stilbene) trimers and their spin-coated organic light-emitting diode (OLED) device performances. Transient absorption profiles of spirally configured, ter-( cis-stilbene) were studied by pulse radiolysis. The emission profiles after charge recombination of their incipient radical ions in benzene provides insights into the emission mechanism and efficiency in OLED devices. Blue-, sky blue-, and green-emitting OLED devices for a maximum external quantum efficiency are 4.32%, 4.70%, and 2.77%, respectively, by solution process.