Title D–A–D’ TADF emitters for LEEC fabrication: Meta vs ortho-linking controls color and efficiency
Authors Rabiei, Marzieh ; Hosseinnezhad, Mozhgan ; Ebrahimi-Kahrizsangi, Reza ; Nasiri, Sohrab ; Padgurskas, Juozas ; Rukuiza, Raimundas
DOI 10.1016/j.rineng.2025.107598
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Is Part of Results in engineering.. Amsterdam : Elsevier. 2025, vol. 28, art. no. 107598, p. 1-15.. ISSN 2590-1230
Keywords [eng] AIE ; Ir complex ; LEECs ; Mechanochromic ; Meta ; Ortho ; TADF
Abstract [eng] Dual-emissive cores based on isophthalonitrile and phthalonitrile in the meta and ortho positions, respectively, were designed and developed as thermally activated delayed fluorescence (TADF) emitters. The incorporation of 50 wt.% of the ionic complex [Ir(buoppy)2(dmapzpy)][PF6] into the blue emitting meta-substituted dye 4-(9H-carbazol-9-yl)-6-(3,6-di‑tert‑butyl‑9H-carbazol-9-yl)isophthalonitrile , and the green emitting ortho-substituted dye 3-(9H-carbazol-9-yl)-6-(3,6-di‑tert‑butyl‑9H-carbazol-9-yl)phthalonitrile significantly enhanced their photoluminescence quantum yields (PLQYs), reaching up to 79 %, especially for the doped meta-emitter. Tuning of the emission color from blue to green was achieved by substituting the acceptor core position, and a mechanochromic response was observed. The meta-substituted emitter exhibited a more rigid structure than its ortho counterpart, as evidenced by a higher glass transition temperature (Tg), due to the reduced conformational twisting between the core and the various carbazole donor derivatives. This rigidity of meta limited the spatial separation of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), facilitating enhanced overlap. Both emitters featured small singlet–triplet energy gaps (ΔEST < 0.11 eV), enabling efficient reverse intersystem crossing (RISC) and moderate to long delayed fluorescence lifetimes. Solution-processed light emitting electrochemical cells (LEECs) fabricated with these emitters achieved a maximum external quantum efficiency (EQEmax) of 6.99 %, with stable blue emission corresponding to CIE coordinates of (0.190, 0.382).
Published Amsterdam : Elsevier
Type Journal article
Language English
Publication date 2025
CC license CC license description