Asymmetric Host Molecule Bearing Pyridine Core for Highly Efficient Blue Thermally Activated Delayed Fluorescence OLEDs

Abstract

In this study,t wo host materials, pCzBzbCz and pCzPybCz,a re synthesized to achieve ah ighe fficiency and long lifetimeo fb lue thermally activated delayed fluorescence organic light-emitting diodes (TADF-OLEDs). The molecular design strategy involves the introduction of ap yridine group into the core structure of pCzPybCz as an electron-withdrawingu nit, anda ne lectron-donating phenyl group into the structure of pCzBzbCz.T hese host materials demonstrate good thermals tability and high triplet energy (T 1 = 3.07 eV for pCzBzbCz and 3.06 eV for pCzPybCz)f or the fabrication of blue TADF-OLEDs. In particular, pCzPybCzbased OLED devices demonstrate an externalq uantum efficiency (EQE) of 22.7 %a nd an operational lifetime of 24 h (LT 90 ,t ime to attain 90 %o fi nitial luminance)a ta ni nitial luminanceo f1 000 cd m À2 .T his superior lifetimec ould be explained by the CÀNb ond dissociation energy (BDE) in the host molecular structure. Furthermore, am ixed-hosts ystem using the electron-deficient 2,4-bis(dibenzo[b,d]furan-2-yl)-6phenyl-1,3,5-triazine(DDBFT)i sp roposed to inhibit the formationo ft he anion state of our host materials.I ns hort, the deviceo perational lifetime is further improvedb ya pplying DDBFT. Thec arbazole-based asymmetric host molecule containingapyridine core realizes ah igh-efficiency blue TADF-OLED showing ap ositive effect on the operating lifetime, and can provide useful strategies for designing new host materials.

Recent Advances on Furan-Based Visible Light Photoinitiators of Polymerization

“…Based on its absorption extending between 300 and 450 nm with an absorption maximum located at 373 nm, this dye was thus appropriate for photopolymerization experiments carried out at 365, 385, and 405 nm (See Figure 2). effect transistors [213,214], the design of fluorescent materials [215] and light-emitting materials [216,217] or host materials [218] for organic light-emitting diodes. Furan exhibits a low toxicity, even if recent reports have demonstrated that furan can be formed during the thermal treatment of food and can be carcinogenic [219].…”

“…Furan is a heterocyclic five-membered ring that is extensively used for the design of anti-inflammatory and antimicrobial agents [211]. Furan was also used for the design of semi-conducting materials for organic solar cells [212] and field effect transistors [213,214], the design of fluorescent materials [215] and light-emitting materials [216,217] or host materials [218] for organic light-emitting diodes. Furan exhibits a low toxicity, even if recent reports have demonstrated that furan can be formed during the thermal treatment of food and Catalysts 2023, 13, 493 3 of 28 can be carcinogenic [219].…”

Status and Challenges of Blue OLEDs: A Review

“…However, a couple TADF-based OLEDs show a fair lifetime with high current efficacy in the sky-blue region. Yoon et al reported a lifetime of 24 h and CE max of 42 cd/A corresponding to a CIE y of 0.35 by using a 30 wt% DBA-BI emitter doped in a pCzPybCz host [ 113 ].…”

Effects of variation in phenylpyridinyl and di-tert-butyl-carbazolyl substituents of benzene on the performance of the derivatives in colour-tuneable white and exciplex-based sky-blue light-emitting diodes

“…Several other carbazole and pyridine derivatives were successfully applied in OLEDs. 24–26 However, they were typically used as charge-transporting materials and as hosts. 27,28 The derivatives of carbazole and pyridine were reported as emitters for ultraviolet OLEDs with electroluminescence (EL) peaking at 394 nm and a narrow full-width at half maximum (FWHM) of 17 nm.…”