Rational molecular design of TADF emitters towards highly efficient yellow electroluminescence with a nearly 30% external quantum efficiency and low roll-off. Issue 31 (20th July 2022)

• Record Type: Journal Article
• Authors: Xie, Honghui; Huang, Zhongyan; Li, Nengquan; Hua, Tao; Miao, Jingsheng; Yang, Chuluo
• Is Part Of: Journal of materials chemistry. Volume 10:Issue 31(2022)
• Page Start: 11239
• Page End: 11245
• Publication Date: 2022-07-20
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/d2tc02045a
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : A boron-based thermally activated delayed fluorescence emitter was developed for highly efficient yellow organic light-emitting diodes by employing a strong donor with large steric hindrance. Abstract : Developing a feasible strategy to realize thermally activated delayed fluorescence (TADF) emitters with high efficiency and tunable emission colors is essential for organic light-emitting diodes (OLEDs). In this study, based on a rigid planar acceptor of 2, 12-di- tert -butyl-5, 9-dioxa-13 b -boranaphtho[3, 2, 1- de ]anthracene and phenoxazine-derived donors, two new TADF emitters, namely PXZBO1 and PXZBO2, featuring tunable emission were designed and prepared for highly efficient OLEDs. The donor engineering by attaching additional electron-donating tert -butyldiphenylamine groups to the donor of PXZBO1 successfully results in PXZBO2 with significantly redshifted emission. PXZBO1 and PXZBO2 are characterized by highly twisted molecular structures to achieve a very small singlet–triplet splitting of 0.01 eV and enable efficient TADF, with high photoluminescence quantum yields of over 94% and fast reverse intersystem crossing rates of over 10 6 s −1 in doped films. As a result, TADF OLEDs using PXZBO1 and PXZBO2 as emitters achieved maximum external quantum efficiencies of 25.9% and 29.7%, peaking at 503 and 563 nm, respectively, with roll-off efficiencies of only ∼11% at a luminance of 1000 cd m −2 . The excellent device performance renders PXZBO2 one of the most efficient yellow TADF emitters ever reported.