Flexible diphenylsulfone versus rigid dibenzothiophene-dioxide as acceptor moieties in donor -acceptor -donor TADF emitters for highly efficient OLEDs
Journal
ORGANIC ELECTRONICS
Journal Volume
83
Date Issued
2020
Author(s)
Gudeika, Dalius
Lee, Pei-Hsi
Chen, Chia-Hsun
Chiu, Tien-Lung
Baryshnikov, Glib, V
Minaev, Boris F.
Agren, Hans
Volyniuk, Dmytro
Bezvikonnyi, Oleksandr
Grazulevicius, Juozas, V
Abstract
Flexible versus rigid molecular structures of donor-acceptor-donor type compounds are investigated with respect to efficiency of thermally activated delayed fluorescence (TADF) by theoretical and experimental approaches. Three highly efficient TADF emitters based on flexible diphenylsulfone and rigid dibenzothiophene-dioxide as acceptor units and di-tert-butyldimethyldihydroacridine as donor moiety were designed and synthesized. Despite they showed similar singlet-triplet splitting (0.01–0.02 eV) and high photoluminescence quantum yields in appropriate hosts, maximum external quantum efficiencies as different as 24.1 and 15.9/19.4% were obtained for organic light emitting devices based on these emitters with, respectively, flexible and rigid molecular structures. The high efficiency of the light-emitting compounds with the flexible molecular structure could be traced to the bi-configurational nature of the lowest singlet and triplet states resulting in higher spin-orbit coupling than for molecules with rigid structures. All derivatives showed bipolar charge transport character. High device efficiency with electron mobility of 3 × 10−5 cm2V−1s−1 and hole mobility of 1.3 × 10−4 cm2V−1s−1 at the electric field of 5 × 105 Vcm−1 was recorded for the layer of para-disubstituted diphenylsulfone with flexible molecular structure. This TADF emitter showed an excellent performance in the organic light emitting device, exhibiting a maximum current efficiency, power efficiency, and external quantum efficiency of 61.1 cdA-1, 64.0 lmW−1, and 24.1%, respectively. © 2020 Elsevier B.V.
Subjects
Bipolar charge transport; di-tert-butyldimethyldihydroacridine; Dibenzothiophene dioxide; Diphenylsulfone; Thermally activated delayed fluorescence
Other Subjects
Current density; Efficiency; Electric fields; Fluorescence; Hole mobility; Molecular structure; Organic light emitting diodes (OLED); Spin orbit coupling; Experimental approaches; External quantum efficiency; Organic light-emitting devices; Photoluminescence quantum yields; Rigid molecular structure; Singlet and triplet state; Singlet-triplet splitting; Thermally activated delayed fluorescences; Quantum efficiency
Type
journal article