10.1002/chem.201703270
Chemistry - A European Journal
FULL PAPER
the ‘Fonds der Chemischen Industrie’ (FCI) in the Liebig grant
framework. R.D.C. further acknowledges the program “Ayudas
para la atracción de talento investigador – Modalidad 1 of the
Consejería de Educación, Juventud y Deporte – Comunidad de
Madrid with the reference number 2016-T1/IND-1463”. F.D.M.
and M.L. are grateful to Prof. J.C. Sancho-García for his generous
support. SG thanks Johnson Matthey for the gift of metals.
Computational details. Geometries were optimized with the B3LYP
functional in which the DFT-D3 dispersion correction[27] was included for a
better description of long-range interactions such as CH- interactions
respectively between the dpa and NHC ligands. The effective core
potential SDD was used for the copper atom and the 6-31+G(d,p) basis
set for carbon, nitrogen, hydrogen, phosphor and oxygen atoms. Recently,
we have shown that charge transfer states upon excitation play a crucial
role in the photophysical properties of [Cu(NHC)(dpa)]+ complexes.
Therefore, TD-DFT calculations were performed with the PBE0 functional
that has been shown to be particularly relevant to describe TADF event.[22]
Both S0-S1 and S0-T1 transitions were considered and their natures were
assigned plotting the Natural Transition Orbital analysis, in which
molecular orbital contributions to a given transition are summed and
weighted according to their CI coefficients. TADF were calculated from
both optimized S1 and T1 energies. The former was calculated using the
implemented TD-DFT gradients while the latter was obtained from open-
spin-relaxed open shell calculations. Calculations were performed using
the Gaussian 09 Revision D.01 package.[28] Visualization were carried out
with the VMD program. [29]
Keywords: Copper(I) complexes • photoluminescence •
Thermally activated delayed fluorescence • density functional
theory • light-emitting electrochemical cell
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Device preparation and analysis. Double layer LECs were fabricated as
follows. ITO coated glass plates were patterned by conventional
photolithography (Naranjo Substrates). The substrates were cleaned by
using sequential ultrasonic baths, namely in water-soap, water, ethanol,
and propan-2-ol solvents. After drying, the substrates were placed in a
UV–ozone cleaner (Jetlight 42-220) for 8 min. An 100 nm layer of
PEDOT:PSS was doctor-bladed onto the ITO-glass substrate to increase
the device preparation yield (400 m substrate distance and a speed of 10
mm/s). The luminescent layer was entirely prepared with copper(I)
complexes. The active layer was deposited by means of doctor blading
technique (600 m substrate distance and a speed of 20 mm/s) reaching
a thickness of 90-100 nm. These conditions resulted in homogenous thin
films with a roughness less than 5 %, having no apparent optical defects.
The latter was determined using the profilometer DektakxT from Bruker.
Once the active layer was deposited, the samples were transferred into an
inert atmosphere glovebox (<0.1 ppm O2 and H2O, Innovative Technology).
Aluminum cathode electrode (90 nm) was thermally evaporated using a
shadow mask under high vacuum (<1 x 10–6 mbar) using an Angstrom
Covap evaporator integrated into the inert atmosphere glovebox. Time
dependence of luminance, voltage, and current was measured by applying
constant and/or pulsed voltage and current by monitoring the desired
parameters simultaneously by using Avantes spectrophotometer
(Avaspec-ULS2048L-USB2) in conjunction with a calibrated integrated
sphere Avasphere 30-Irrad and Botest OLT OLED Lifetime-Test System.
Electroluminescence spectra were recorded using the same
spectrophotometer. Electrochemical impedance spectroscopic assays
were carried out with a potentiostat/galvanostat (PGSTAT30, Autolab)
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This work was supported by the "Ministère de la Recherche et des
Nouvelles Technologies", CNRS (Centre National de la
Recherche Scientifique) and the LABEX SynOrg (ANR-11-LABX-
0029). We thank the “Agence Nationale de la Recherche”, within
the CSOSG program (ANR-12-SECU-0002-02), the ANR
program (ANR-15-CE39-0006) and the “Région Basse-
Normandie” for their funding (F.S. and M.E.). M.L. acknowledges
SeRC (Swedish e-Science Research Center) for funding. F.D.M.
thanks the Swedish Research Council (Grant No. 621-2014-
4646). F.D.M. and M.L. acknowledges SNIC (Swedish National
Infrastructure for Computing) for providing computer resources
(snic001-12-192). RDC and MDW acknowledge the support by
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