LAUSR

To achieve high-efficiency deep-blue electroluminescence satisfying Rec.2020 standard blue gamut, we developed two TADF emitters, 5-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-10,10-diphenyl-5,10-dihydrodibenzo[b,e][1,4]azasiline (TDBA-PAS) and 10-(2,12-di-tert-butyl-5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracen-7-yl)-9,9-diphenyl-9,10-dihydroacridine (TDBA-DPAC). Inherited from their parented organoboron multi-resonance core, both emitters show very promising deep-blue emissions with relatively narrow full width at half-maximum (FWHM, ∼ 50 nm in solution), high photoluminescence quantum yield (up to 92.3%) and short emission lifetime (≤ 2.49 μs) with fast RISC (> 106 s-1 ) in doped films. More importantly, replacing the spiro-centered sp3 C atom (TDBA-DPAC) with the larger radius sp3 Si atom (TDBA-PAS), enhanced conformational heterogeneities in bulky group shielded TADF molecules were observed in solution, doped film and device. Consequently, OLEDs based on TDBA-PAS retain high maximum external quantum efficiencies around 20% with suppressed efficiency roll-off and color index close to Rec.2020 blue gamut over a wide doping range of 10-50 wt%. This study highlighted a new strategy to restrain spectral broadening and red-shifting and efficiency roll-off in the design of deep-blue TADF emitters. This article is protected by copyright. All rights reserved.