An Approach for Measuring the Dielectric Strength of OLED Materials.

Surface roughness of electrodes plays a key role in the dielectric breakdown of thin-film organic devices. The rate of breakdown will increase when there are stochastic sharp spikes on the surface of electrodes. Additionally, surface having spiking morphology makes the determination of dielectric strength very challenging, specifically when the layer is relatively thin. We demonstrate here a new approach to investigate the dielectric strength of organic thin films for organic light-emitting diodes (OLEDs). The thin films were deposited on a substrate using physical vapor deposition (PVD) under high vacuum. The device architectures used were glass substrate/indium tin oxide (ITO)/organic material/aluminum (Al) and glass substrate/Al/organic material/Al. The dielectric strength of the OLED materials was evaluated from the measured breakdown voltage and layer thickness.

A new molecular design based on hybridized local and charge transfer fluorescence for highly efficient (>6%) deep-blue organic light emitting diodes.

A deep-blue emitter was developed by modifying carbazole nuclear positions C2 & C7 with a triphenylamine donor and C3 & C6 with a cyano acceptor. The molecular design features cross-conjugated localized and charge transfer chromophores which results in a hybridized local charge transfer (HLCT) excited state. An organic light emitting diode (OLED) using this material exhibited high external quantum efficiency (6.5%) with excellent color saturation (CIEy ∼ 0.06) and small full-width at half maximum (48 nm).