Rational
Design of Strongly Blue-Emitting Cuprous
Complexes with Thermally Activated Delayed Fluorescence and Application
in Solution-Processed OLEDs
Xu-Lin Chen
Rongmin Yu
Qi-Kai Zhang
Liu-Jiang Zhou
Xiao-Yuan Wu
Qing Zhang
Can-Zhong Lu
10.1021/cm4024309.s002
https://acs.figshare.com/articles/dataset/Rational_Design_of_Strongly_Blue_Emitting_Cuprous_Complexes_with_Thermally_Activated_Delayed_Fluorescence_and_Application_in_Solution_Processed_OLEDs/2368486
A new series of strongly greenish-blue
to blue emitting Cu(NN)(POP)<sup>+</sup> (POP = bis[2-(dipenylphosphino)phenyl]ether)
complexes containing
N-linked 2-pyridyl pyrazolate diimine ligands [Cu(pypz)(POP)]BF<sub>4</sub> (<b>1</b>), [Cu(pympz)(POP)]BF<sub>4</sub> (<b>2</b>), and [Cu(pytfmpz)(POP)]BF<sub>4</sub> (<b>3</b>) (pypz =
1-(2-pyridyl)pyrazole, pympz = 3-methyl-1-(2-pyridyl)pyrazole, and
pytfmpz = 3-trifluoromethyl-1-(2-pyridyl)pyrazole) have been designed
and synthesized. Their structural, electrochemical, and photophysical
properties have been characterized. The complexes <b>1</b>–<b>3</b> exhibit high photoluminescence quantum yields (PLQYs) at
room temperature both in nitrogen-saturated CH<sub>2</sub>Cl<sub>2</sub> (up to 45%) and in neat solid (up to 87%), which are comparable
to the reported highest values for the cuprous complexes. The temperature
dependence of spectroscopic properties and emission decay behaviors
reveal the presence of two thermally equilibrated emitting states.
At temperatures below 150 K, the lowest triplet state (T<sub>1</sub>) is the predominant emitting state resulting in the typical phosphorescence
with the emission decay times in the order of hundreds of microseconds.
However, at ambient temperature, the lowest singlet state (S<sub>1</sub>), which lies only about 0.17–0.18 eV above the T<sub>1</sub> state, is populated thermally and in turn generates efficient thermally
activated delayed fluorescence (TADF), and the emission decay times
are reduced dramatically to, e.g., 12.2 μs for <b>2</b>. Solution-processed OLEDs containing <b>1</b>–<b>3</b> in the emissive layer demonstrated excellent device performances
by taking advantage of the singlet harvesting mechanism, among which
the electroluminescent device using <b>3</b> shows a peak external
quantum efficiency (EQE) of 8.47%, a peak current efficiency (CE)
of 23.68 cd/A, and a maximum brightness of 2033 cd/m<sup>2</sup>.
2013-10-08 00:00:00
emission decay times
temperature dependence
triplet state
OLED
electroluminescent device
EQE
pyridyl
singlet state
photophysical properties
ambient temperature
Thermally Activated
photoluminescence quantum yields
150 K
emission decay behaviors
TADF
T 1 state
quantum efficiency
PLQY
emissive layer
CH
singlet harvesting mechanism
device performances
cuprous complexes
Cu
spectroscopic properties
CE
POP
Rational Design
room temperature