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Hybridised‐Local and Charge‐Transfer Excited States in Donor‐Spacer‐Acceptor Molecules for Efficient OLEDs: Combined Experimental and Theoretical Study
Author(s) -
Thanikachalam Venugopal,
Jeeva Palanivel,
Jayabharathi Jayaraman
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201601842
Subject(s) - triphenylamine , excited state , electroluminescence , oled , acceptor , chemistry , molecule , photochemistry , materials science , atomic physics , organic chemistry , physics , layer (electronics) , condensed matter physics
Abstract Donor‐spacer‐acceptor (D‐π‐A) architecture consists of triphenylamine (TPA) and phenanthrimidazole (MPPPI) namely, para ‐linked p TPA‐MPPPI and meta ‐linked m TPA‐MPPPI was designed and synthesized using phenyl as spacer. The photophysical and electroluminescent behaviour of these two isomers were comparatively investigated. These compounds exhibit excellent thermal stabilities, decomposition temperature, T d ‐ 426°C ( m TPA‐MPPPI); T d ‐ 432 °C ( p TPA‐MPPPI) with high glass transition temperature, T g ‐ 124°C ( m TPA‐MPPPI); T g ‐ 115°C ( p TPA‐MPPPI). Meta linked m TPA‐MPPPI isomer exhibit NUV emission compared to para linked isomer, however, with the loss of efficiency. Theoretical calculation and photophysical experiments have been implemented to verify the excited state properties of p TPA‐MPPPI and m TPA‐MPPPI and indicates that these twisting D‐π‐A molecules exhibit a hybridised local and charge transfer (HLCT) excited state. The m TPA‐MPPPI based device exhibit EL emission at 407 nm with FWHM of 42 nm corresponding to CIE coordinates of (0.16, 0.087) whereas the p TPA‐MPPPI device exhibit higher electroluminescent efficiencies, η c = 3.10 cd A ‐1 , η p = 3.94 lm W ‐1 and η ex = 4.05 %.