Recent Progress in Phosphorescent Organic Light‐Emitting Devices

Abstract

Organic light‐emitting devices (OLEDs) are solid‐state light‐emitting devices based on organic semiconductors. Recent rapid advances in materials chemistry have enabled white OLEDs to be used for general lighting and large‐area flat panel display. White OLED panel efficacy has reached 90 lm W–1, and a tandem white OLED panel has achieved a lifetime of over 100000 h at 1000 cd m–2. LG is set to launch a 55″ OLED TV in 2013, and OLEDs will be expected to make bigger breakthroughs. Although white OLED panels show superior performance, there is still much room (nearly 160 lm W–1) for improvement, in view of the theoretical limit of 248 lm W–1. To reach this objective, OLEDs need to achieve three goals: (1) high internal quantum efficiency, (2) low operation voltage, and (3) high light‐outcoupling efficiency at the same time. For organic chemists creating new organic semiconductors, issues (1) and (2) are particularly important because these relate to materials chemistry. Here we review recent developments in phosphorescent OLED technology, especially from materials chemistry.

Recent Advances in Polymer Organic Light-Emitting Diodes (PLED) Using Non-conjugated Polymers as the Emitting Layer and Contrasting Them with Conjugated Counterparts

“…22 In order to solve this problem, organometallic complexes built with heavy metals such as iridium and platinum are employed as phosphorescent emitters in OLED devices. 6,22,23 The large spin-orbit coupling constants (f) of those metals increase the rate of intersystem-crossing (ISC) to shorten phosphorescence lifetime to useful microsecond regimes. 6,22,24 As a result, phosphorescent OLEDs can achieve 100% internal quantum efficiency (IQE) and devices showing stellar external quantum efficiencies (EQEs) of >30% have been reported.…”

“…6,22,23 The large spin-orbit coupling constants (f) of those metals increase the rate of intersystem-crossing (ISC) to shorten phosphorescence lifetime to useful microsecond regimes. 6,22,24 As a result, phosphorescent OLEDs can achieve 100% internal quantum efficiency (IQE) and devices showing stellar external quantum efficiencies (EQEs) of >30% have been reported. 5,25 Lai et al prepared a polystyrene functionalized with dendronized iridium(III) phosphor (DIr-P1, Fig.…”

“…Furthermore, being an energy-efficient technology, OLED lighting will help alleviate power consumption that at currently about 20% of total electricity consumption is devoted solely to lighting purposes. 6 Apart from device efficiency, the ease of fabrication also plays an essential role in the marketability of OLED technology, because it reduces the device manufacturing cost. In this regard, the wet process (spin-casting or inkjet printing) is more beneficial than the dry process (vacuum thermal deposition), especially in the case of large-area display devices.…”

Recent progress of pyrimidine derivatives for high-performance organic light-emitting devices

“…[1][2][3][4][5][6][7][8] Moreover, flexible and transparent OLEDs can be fabricated, and printable OLEDs can also be used in future applications. Until recently, phosphorescent emitters containing platinum heavy metals, such as iridium and platinum, were absolutely required for high-efficiency OLEDs to realize internal quantum efficiency (IQE) of 100% since these rare heavy metals can harvest all electrogenerated molecular singlet and triplet excitons ( Fig.…”

Inhibition of solution-processed 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile crystallization by mixing additives for hole injection layers in organic light-emitting devices

“…[1][2][3] To fabricate highly efficient devices, the incorporation of hole injection layers (HILs) is indispensable because these significantly improve the characteristics of hole injection from the anode to the emitting layer, leading to lower driving voltages and improved charge recombination balance. To date, various HILs have been reported, [4][5][6][7][8][9][10][11][12][13][14][15] and, among these, 1,4,5,8,9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) has been employed in HILs (leading to low driving voltage) 4,[16][17][18][19][20][21][22] since the first application of OLED by LG Chemical Ltd. 22 HAT-CN was first reported by Czarnik and co-workers 23 and its characterization has been investigated in various studies.…”