Two
tetradentate Pt(II) complexes with peripheral bulky-group hindrances
[Pt(pzpyOczpy-B1) and Pt(pzpyOczpy-B2)] were synthesized and fully
investigated for their structural and blue phosphorescent properties.
Both X-ray crystallography and computational simulation revealed that
bulky substituents incorporated into the C-pyrazolyl and C-pyridinyl
positions lie out of the cyclometallated plane, thus alleviating the
intramolecular distortions as well as reducing the intermolecular
interaction in the solid state. In dichloromethane, their emission
peaks at 460 nm with a narrow full width at half-maximum (FWHM) of
less than 50 nm, and the photoluminescent quantum yields are over
95% with short decay lifetimes (<5 μs). Solution-processed
blue devices are fabricated based on the two complexes. Device A based
on Pt(pzpyOczpy-B1) shows excellent electroluminescent performances
with the maximum current efficiency, power efficiency, and external
quantum efficiency of 47.0 cd/A, 24.6 lm/W, and 22.9%, respectively.
The understanding on inert peripheral hindrances provides an effective
approach to designing Pt(II) complexes for high-quality blue phosphorescent
emitters.
Efficient and durable OLEDs of cyan, greenish yellow, yellow and white colors were fabricated in simple structures with Pt–Cpy bonded complexes, giving state-of-the-art tuning the color of electroluminescence.
Poly(3,4ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) has been intensively studied for its thermoelectric applications. Structural modulation to improve crystalline ordering, chain conformation and film morphology is a promising way to decouple the trade‐off between conductivity and Seebeck coefficient and thus improve the thermoelectric power factor. Post treatment with ionic liquid ([CoCl2 ⋅ 6H2O]:[ChCl]) bearing cobalt‐containing anions resulted in a remarkable enhancement of the power factor to 76.8 μW m−1 K−2. This IL combines the influence of a high‐boiling polar organic solvent and diffusing ions. A high σ mainly resulted from the efficient removal of PSS chains, ordering of the structure and delocalization of bipoloran‐dominant transport after conformational change. The increase in S was not due to dedoping of PEDOT chains, but rather the sharp feature of the density of states at the Fermi level induced by ion‐exchange with unconventional anions.
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