Oliver Molt

High‐Efficiency Blue and White Organic Light‐Emitting Devices Incorporating a Blue Iridium Carbene Complex

High-effi ciency white organic light-emitting devices (OLEDs) have great potential for energy saving solid-state lighting and eco-friendly fl at-display panels. [ 1 ] In addition, white OLEDs are expected to open new designs in lighting technology, such as transparent lighting panels or luminescent wallpapers because of being able to form paper-like thin fi lms. Phosphorescent OLED technology is an imperative methodology to realize higheffi ciency white OLEDs because phosphors, such as fac -tris(2phenylpyridine)iridium( III ) [Ir(ppy) 3 ] and iridium( III )bis(4,6(difl uorophenyl)pyridinatoN , C 2 ′ )picolinate (FIrpic) enable an internal effi ciency as high as 100% converting both singlet and triplet excitons into photons. [ 2 ] There are two effective approaches to obtain white OLEDs by using phosphors. One is to combine a blue fl uorophore and phosphors for the other colors, a so-called hybrid white OLED. [ 3 ] A key requirement is the use of a blue fl uorophore with higher triplet energy ( E T1 ) than that of the other phosphors. The blue fl uorophore also needs to have a high photoluminescent quantum yield ( η PL ). Schwartz and coworkers reported hybrid white OLEDs with a power effi ciency at 1000 cd m − 2 ( η p,1000 ) of 22 lm W − 1 (external quantum effi ciency (EQE) of 10.4%) by using N , N ′ -di-1-naphthalenylN , N ′ -diphenyl-[1,1 ′ :4 ′ ,1 ′ ′ :4 ′ ′ ,1 ′ ′ ′ -quaterphenyl]-4,4 ′ ′ ′ -diamine (4P-NPD) as a blue fl uorophore, and Ir(ppy) 3 and iridium( III ) bis(2-methyldibenzo-[ f , h ]quinoxaline)(acetylacetonate) [Ir(MDQ) 2 ( acac)] as green and red phosphors, respectively. [ 4 ]

Controlling the radiative rate of electrophosphorescent organometallic complexes by engineering the singlet-triplet splitting

We address the role of singlet-triplet splitting in controlling the radiative rate for deep-blue electrophosphorescent metal complexes. An enhanced radiative rate correlates with a small splitting, highlighting the road map to efficient electrophosphorescence.

Deep Blue Phosphorescent OLEDs with Improved Device Stability

Cyclometallated iridium N-heterocyclic carbene (NHC)-complexes have become known as efficient deep blue triplet emitters in OLEDs. Herein we discuss new materials and device setups for carbene-based deep blue OLEDs with improved stability and lifetime.