Simultaneous Optimization of Charge‐Carrier Balance and Luminous Efficacy in Highly Efficient White Polymer Light‐Emitting Devices

The use of white organic light-emitting devices (WOLEDs) for solid-state lighting applications is becoming increasingly attractive, [ 1 − 5 ] given that legislation in more countries is banning the use of ineffi cient incandescent lamps. Moreover, since fl uorescent lamps involve the use of mercury and its disposal represents a great challenge, many scientists have been working aggressively to make the replacement of the fl uorescent light sources by WOLEDs a reality. Indeed, the effi ciency of multilayer vacuum-evaporated WOLEDs based on small molecules has been greatly improved in the past several years [ 6 − 10 ] and has already exceeded that of fl uorescent lamps. [ 11 ] In contrast, despite many unique advantages, such as low-cost manufacturing using solution-processing techniques, easy processability over large-areas by spin-coating or ink-jet printing, compatibility with fl exible substrates, a relatively small amount of wasted material, and precise control of the doping level, the application of white polymer light-emitting diodes (WPLEDs) is still severely hindered by the relatively low device effi ciency. [ 3 , 12 − 16 ]

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