Advance in Fluorene-Based Blue Electroluminescent Materials

Since the earliest reports of organic/polymeric light emitting diodes(OLEDs/PLEDs),fabricating ultrathin,full color,free-angle and large-area displays have stimulated intensive research interest around the world.To realize full color displays,high performance red,green,and blue light-emitting materials are required.In contrast to red and green emitters,only a few blue emitters showed efficient blue light-emitting materials can be used as not only emissive layer in OLEDs/PLEDs,but also host materials for efficient blue and white light source.Among the promising blue emitters,fluorene-based oligomers and polymers have displayed excellent thermal stabilities,fluorescent quantum yields,and electroluminescent behaviors.However,the fluorene-based electroluminescent blue materials usually exhibited inferior electroluminescence efficiency,poor color purity and spectral stability caused by weak charge injection and transport,aggregation/excimer formation,and/or the fluorenone of photooxidized fluorene.The progress of the fluorene-based blue light-emitting compounds and polymers was reviewed.The key point of the review was paid to the design,synthesis,and electroluminescent performance of oligofluorenes and polyfluorenes with electron-donors and/or acceptors.A large number of literatures have demonstrated that the materials containing both electron-donating and electron-withdrawing segments could have better performance than those corresponding hole-only or electron-only materials.