High Power Efficiency Solution-Processed Blue Phosphorescent Organic Light-Emitting Diodes Using Exciplex-Type Host with a Turn-on Voltage Approaching the Theoretical Limit.
Three solution-processable exciplex-type host materials were successfully designed and characterized by equal molar blending hole transporting molecules with a newly synthesized electron transporting material, which possesses high thermal stability and good film-forming ability through a spin-coating technique. The excited-state dynamics and the structure-property relationships were systematically investigated. By gradually deepening the highest occupied molecular orbital (HOMO) level of electron-donating components, the triplet energy of exciplex hosts were increased from 2.64 to 3.10 eV. Low temperature phosphorescence spectra demonstrated that the excessively high triplet energy of exciplex would induce a serious energy leakage from the complex state to the constituting molecule. Furthermore, the low energy electromer state, which only exists under the electroexcitation, was found as another possible channel for energy loss in exciplex-based phosphorescent organic light-emitting diodes (OLEDs). In particular, as quenching of the exciplex-state and the triplet exciton were largely eliminated, solution-processed blue phosphorescence OLEDs using the exciplex-type host achieved an extremely low turn-on voltage of 2.7 eV and record-high power efficiency of 22.5 lm W(-1), which were among the highest values in the devices with identical structure.
School of Chemistry and Chemical Engineering, Southeast University , Nanjing, Jiangsu, P. R. China , 211189.
Xinxin
X
Ban
School of Chemistry and Chemical Engineering, Southeast University , Nanjing, Jiangsu, P. R. China , 211189.
Kaiyong
K
Sun
School of Chemistry and Chemical Engineering, Southeast University , Nanjing, Jiangsu, P. R. China , 211189.
Yueming
Y
Sun
School of Chemistry and Chemical Engineering, Southeast University , Nanjing, Jiangsu, P. R. China , 211189.
Bin
B
Huang
National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications , Nanjing, Jiangsu, P. R. China , 210023.
Shanghui
S
Ye
National Synergistic Innovation Center for Advanced Materials, Nanjing University of Posts and Telecommunications , Nanjing, Jiangsu, P. R. China , 210023.
Min
M
Yang
School of Chemistry and Chemical Engineering, Southeast University , Nanjing, Jiangsu, P. R. China , 211189.
Wei
W
Jiang
blue phosphorescence; exciplex; power efficiency; solution process; turn-on voltage