Tai Peng

Abstract: Three isomeric boron‐containing thermally activated delayed fluorescent (TADF) emitters, namely m‐AC‐DBNA, p‐AC‐DBNA, and m′‐AC‐DBNA, are constructed by incorporating an electron‐donor acridine (AC) moiety into meta‐, para‐, or meta′‐positions of an electron‐accepting boron‐embedded rigid framework. The substitutional positions are found to dramatically affect thermal, photophysical, and electroluminescent (EL) properties. The experimental results show that the para‐substituted compound (p‐AC‐DBNA) exhibits higher decomposition temperature, higher photoluminescence (PL) quantum efficiencies, smaller singlet–triplet energy splitting, shorter delayed fluorescence lifetimes as well as a fast reverse intersystem crossing rate of over 106 s−1, compared to the meta‐isomers (m‐AC‐DBNA and m′‐AC‐DBNA). Bright and highly efficient organic light‐emitting diodes (OLEDs) with external quantum efficiencies (EQEs) up to 20.5% and 14.1% are achieved by employing p‐AC‐DBNA as doped and nondoped emitters in sky‐blue OLEDs, respectively. Moreover, excellent doping‐concentration independent EL properties and very low efficiency roll‐off at a high luminance are achieved. This isomeric strategy provides a simple method to extend structural diversity of highly efficient TADF emitters, optimize optoelectronic properties, and demonstrate the relationship of delayed fluorescence lifetime and efficiency roll‐off of the TADF devices. The three isomers also display distinct temperature‐dependent emission and mechanochromism.

TL;DR: With the aid of borylation and oxidative coupling reactions, six new polycyclic aromatic hydrocarbons doped by nitrogen-boron-nitrogen (NBN) units were achieved.

TL;DR: Mechanistic insight into these highly regioselective transformations was obtained from kinetic data and through computational studies.

TL;DR: In this paper, the first examples of organoboron-based photochromic polymers are reported, which display thermally reversible photochromism, switching color from colorless to deep blue, and fluorescence from bright sky blue to deep green.