title: Very High Brightness Quantum Dot Light-Emitting Devices via Enhanced Energy Transfer from a Phosphorescent Sensitizer.
abstract: We demonstrate very efficient and bright quantum dot light-emitting devices (QDLEDs) with the use of a phosphorescent sensitizer and a thermal annealing step. Utilizing CdSe/CdS core/shell quantum dots with 560 nm emission peak, bis(4,6-difluorophenylpyridinatoN,C2) picolinatoiridium as a sensitizer, and thermal annealing at 50 °C for 30 min, green-emitting QDLEDs with a maximum current efficiency of 23.9 cd/A, a power efficiency of 31 lm/W, and a brightness of 65,000 cd/m(2) are demonstrated. The high efficiency and brightness are attributed to annealing-induced enhancements in both the Forster resonance energy transfer (FRET) process from the phosphorescent energy donor to the QD acceptor and hole transport across the device. The FRET enhancement is attributed to annealing-induced diffusion of the phosphorescent material molecules from the sensitizer layer into the QD layer, which results in a shorter donor-acceptor distance. We also find, quite interestingly, that FRET to a QD acceptor is strongly influenced by the QD size, and is generally less efficient to QDs with larger sizes despite their narrower bandgaps.
authors.affiliation: Department of Electrical and Computer Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Hossein
authors.initials: H
authors.lastname: Zamani Siboni
authors.affiliation: Department of Electrical and Computer Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Bahareh
authors.initials: B
authors.lastname: Sadeghimakki
authors.affiliation: Department of Electrical and Computer Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Siva
authors.initials: S
authors.lastname: Sivoththaman
authors.affiliation: Department of Electrical and Computer Engineering, University of Waterloo , 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada.
authors.forename: Hany
authors.initials: H
authors.lastname: Aziz
keywords: efficiency; forster energy transfer; organic light-emitting device; phosphorescent OLED; quantum dot light-emitting device