White Organic Light‐Emitting Diodes

Abstract

White organic light-emitting diodes (WOLEDs) offer a range of attractive characteristics and are in several regards conceptually different from most currently used light sources. From an application perspective, their advantages include a high power efficiency that rivals the performance of fluorescent lamps and inorganic LEDs and the potential for a very low cost of manufacturing. As flat-panel light sources they are intrinsically glare-free and generate light over a large area. WOLEDs are constantly improving in terms of performance, durability, and manufacturability, but these improvements require joint research efforts in chemistry and the materials sciences to design better materials as well as in physics and engineering to invent new device concepts and design suitable fabrication schemes, a process that has generated many exciting scientific questions and answers. This article reviews current developments in the field of WOLEDs and puts a special focus on new device concepts and on approaches to reliable and cost-efficient WOLED manufacturing.

Simulating charge transport in organic semiconductors and devices: a review

“…However, their compatibility with flexible substrates and cheap fabrication methods points to future applications in solid-state lighting and flexible displays [7,426,427]. The technological demands placed on such devices are significant, and for white OLEDs (WOLEDs) for solidstate lighting in particular, since lifetimes must be in excess of 10,000 hours and power efficiencies in excess of 100 lumen/Watt to compete with fluorescent tubes [426], while precise control over the colour temperature is desirable [425].…”

“…We now move on consider charge recombination, which occurs in a wide range of bipolar electronic devices, such as OPVs [150], OLEDs [7], and ambipolar OTFTs [151]. In the case of OLEDs and ambipolar OTFTs the recombination of electrons and holes to form excitons does not (usually) involve significant energetic barriers or spatial separation of charges, and as such is usually assumed to be instantaneous for adjacent charges (i.e.…”

Kinetic Monte Carlo study of triplet-triplet annihilation in organic phosphorescent emitters

“…[1][2][3] In these materials, the spin-orbit interaction induced by the heavy-metal atoms gives rise to exciton states with a quantum-mechanically mixed singlet and triplet character. Due to fast intersystem crossing (ISC), singlet states are almost instantaneously converted to triplet states, so that virtually all emission is due to phosphorescence.…”

Tuning Emission Colors from Blue to Green in Polymeric Light-Emitting Diodes Fabricated using Polyfluorene Blends

“…7,11,15,16,26−32 The use of polymer blends represents a relatively inexpensive approach to the preparation of novel polymeric electroluminescent (EL) diodes with acceptable performances. 5,6,8 Furthermore, after the active materials are chosen, the diode architecture must be optimized to improve the device performance in terms of light output, turn-on voltage, whiteness, and brightness properties. 5,6,13,30 Polymers have emerged as a promising technology for large-area diodes and for flexible diodes, 5,33,34 which can be processed using solutionbased and conventional printing techniques (e.g., roll-to-roll or inkjet techniques).…”