True- to Sky-Blue Emitters Bearing the Thiazolo[5,4-d]thiazole Electron Acceptor for Single and Tandem Organic Light-Emitting Diodes

Abstract

A series of emitters displaying efficient photoluminescence (PL) and electroluminescence (EL) into the trueto sky-blue regions is herein described and employed as electroluminescent materials for the fabrication of efficient blue organic light-emitting diodes (OLEDs). The compounds possess linear, yet a twisted, donor−π−acceptor−π−donor (D−π−A−π− D) architecture, where D and A are a (substituted) carbazole (Cz) and thiazolo [5,4-d]thiazole (TzTz) moiety as the electron donor and accepting unit, respectively. D = 9H-carbazol-9-yl and 3,6-ditert-butyl-9H-carbazol-9-yl for compounds TzTz-PCz2 and TzTz-PtbCz2, respectively. In dilute CH 2 Cl 2 solutions, both compounds display intense (PL quantum yield = 60−74%) and short-lived (τ = ca. 0.8−2.0 ns) luminescence arising from an intramolecular charge-transfer ( 1 ICT) excited state and falling into the sky-blue to the greenish-blue region (λ em = 448−502 nm). Compared to the previously reported TzTz-TPA parental emitters that features two triphenylamine (TPA) donor groups, the highly twisted nature and less extended π-conjugation of the donor−acceptor TzTz-PCz2 and TzTz-PtbCz2 counterparts herein presented enable to widen the HOMO−LUMO energy gaps and warrant blue shifting of the emission. Finally, OLED devices fabricated by employing the herein proposed emitters are presented as well with both single-and tandem-device architectures. The so-prepared OLEDs display true-blue to sky-blue EL peaking at λ EL,max = 460 nm (TzTz-PCz2) and 467−470 nm (TzTz-PtbCz2) and achieve maximum external quantum efficiency and luminance of 10.2% and 44,851 cd m −2 (for TzTz-PtbCz2) in the case of a tandem device, respectively, with a mitigated roll-off efficiency. These results demonstrate that the tandem device employing these TzTz donor−acceptor blue emitters raises the feasibility of fluorescent compounds to compete with other potential emitters in practical applications.

Pyrazino[2,3-f][1,10]phenanthroline-based color-tunable thermally activated delayed fluorescence emitters with AIE characteristics for high-efficiency organic light-emitting diodes

“…This alignment implies successful carrier recombination within the EML, effective energy transfer from the host to the guests, and prevention of exciton diffusion to adjacent layers in the tested devices. 72 In addition, devices B, G, and Y have spectral profiles showing a single peak without distinctive features, with respective full width at half maximum (FWHM) values of 70, 97, and 110 nm. The emission colors of the tested devices can be observed from the inset images in Fig.…”

Design of phenanthroline and diindolocarbazole based emitter for efficient upconversion of triplet excitons by improving rISC

“…This alignment suggests that carrier recombination was confined within the EML, successfully preventing exciton diffusion to neighboring layers in both devices. [31] In addition, the green and yellow devices displayed spectral profiles devoid of distinctive features. The respective full width at half maximum (FWHM) are considered 120 and 109 nm.…”

Enhancement of Blue Doping-Free and Hyperfluorescent Organic Light Emitting Diode Performance through Triplet–Triplet Annihilation in the Derivatives of Anthracene and Carbazole

“…The technology of organic light emitting diodes (OLEDs) needs to solve the issue of the stability and efficiency of devices, especially those with the blue color of emission, for the further advancement in the market of displays and lighting devices. − Nowadays, OLED displays and lighting devices waste ca. 50% of their power because of the low efficiency of the blue fluorescent emitters currently used in OLEDs. , In addition, blue pixels often account for ca.…”