Blue organic light emitting diodes: Challenges and future perspectives

Abstract

Imminent global energy-crisis and inefficient energy utilization push the use of smart energy efficient devices for display and lighting applications. Energy efficient organic light emitting diodes (OLEDs) considered as one of the most competitive candidates for new-generation smart displays and particularly for future energy-saving lighting sources.1 Recently much effort has been made to generate white OLEDs comprising of both fluorescent and phosphorescent materials. Efficient blue-emitting materials are extremely essential for commercialization of white OLEDs and play a vital role in energy-efficient solid-state lighting and smart display devices. Molecular designing of efficient deep-blue materials are limited due to their intrinsic wide bandgap, poor carrier charge balance and their low efficiency in the solid state. In recent decades, phenanthroimidazole (PI) based materials have shown tremendous interest (due to ease in chemical/structural modification at N1 and C2 position) to produce efficient deep-blue OLEDs (satisfying the color purity criteria given by National Television System Committee (NTSC) (CIE: 0.14, 0.08) and European Broadcasting Union (EBU) (CIE: 0.15, 0.06 (Fig. 1.)).2 In this presentation, design strategy of PI-based blue/deep-blue emitting materials and their applications in OLEDs will be presented and discussed.