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Optimization of the Substitution Pattern of 1,3‐Disubstituted Imidazo[1,5‐ a ]Pyridines and ‐Quinolines for Electro‐Optical Applications
Author(s) -
Albrecht Georg,
Rössiger Carina,
Herr Jasmin Martha,
Locke Harald,
Yanagi Hisao,
Göttlich Richard,
Schlettwein Derck
Publication year - 2020
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201900677
Subject(s) - photoluminescence , oled , amorphous solid , electroluminescence , materials science , thin film , fluorophore , quantum yield , stacking , intermolecular force , density functional theory , luminescence , molecule , chemistry , optoelectronics , crystallography , computational chemistry , fluorescence , nanotechnology , layer (electronics) , organic chemistry , optics , physics
A series of recently synthesized 1,3‐disubstituted imidazo[1,5‐ a ]pyridines (IPs) and ‐quinolines (IQs) targeting at increased efficiency of luminescence is investigated. The properties of molecules in solution as well as their change in the solid state are reported and assessed regarding possible application in organic electronics. The influence of increased ring size by substitution, e.g., exchanging phenyl to naphthalenyl, as well as pyridyl to quinolinyl moieties, and by means of a larger IQ fluorophore is discussed. A higher oscillator strength and quantum yield can be achieved. Frontier orbital energies are estimated based on cyclic voltammetry and density functional theory (DFT) calculations. Single crystals of molecules are grown. A red‐shift in the photoluminescence spectra found for crystals of IQs compared with those in solution is proposed to be caused by intermolecular coupling based on the parallel stacking of the enlarged fluorophore units. Thin films deposited by physical vapor deposition exhibit similar effects, showing promise as active layers in organic light‐emitting diodes (OLEDs). An amorphous morphology is inferred for these films from both spectral broadening in photoluminescence and atomic force microscopy. An OLED test structure is prepared, using the most efficient IQ lumophore and demonstrating the feasibility of obtaining electroluminescence from such thin films.