Exploiting heterocycle aromaticity to fabricate new hot exciton materials

Abstract

Efficiently harvesting electroluminescent triplet excitons is of great importance for practical application of organic light-emitting diodes (OLEDs). Hot exciton materials are regarded as the up-and-coming new generation luminogens and hold...

The crucial role of non-conjugated functional groups in the triplet manipulation of heterocycle aromaticity hot exciton materials

“…Based on the proposed heterocycle aromaticity design strategy, the excited state energies and electronic transition properties can be rationally regulated using heterocycle cores with dual non-aromaticity in the ground state (S 0 ) and the lowest triplet state (T 1 ) and peripheral functionalization (Scheme 1). 19 Thus a heterocyclic molecular system with HLCT characteristics could be fabricated to obtain a suitable singlet energy gap ( E g ) and a low-lying triplet state as well as corresponding singlet–triplet and triplet–triplet energy gaps (large Δ E ST , Δ E T and small Δ E SmTn ) to achieve blue-emitting hot exciton materials, facilitate efficient hRISC processes and meanwhile avoid unfavorable internal conversion (IC) loss. Herein, we designed a series of pyrazoline derivatives with different substituents at the 5-position sp 3 carbon to systematically investigate the role of non-conjugated functional groups on the fluorescence behavior and exciton dynamics.…”

“…Recently, our group proposed a novel design strategy for exploiting heterocycle aromaticity to fabricate new hot exciton materials. 19 By virtue of heterocycle aromaticity and peripheral functionalization, molecular excited state energetics could be rationally modulated to achieve the desired singlet–triplet energy gaps and consequently fulfil the general requirements for hot exciton materials (Scheme 1). 19–22 Based on such a strategy, several pyrazoline-core hot exciton materials were successfully fabricated and subsequently applied for OLED devices.…”

“…19 By virtue of heterocycle aromaticity and peripheral functionalization, molecular excited state energetics could be rationally modulated to achieve the desired singlet–triplet energy gaps and consequently fulfil the general requirements for hot exciton materials (Scheme 1). 19–22 Based on such a strategy, several pyrazoline-core hot exciton materials were successfully fabricated and subsequently applied for OLED devices. 19 However, detailed guidelines for excited state manipulation and aggregate state properties still remain far from sufficient for implementing rational molecular design.…”

“…19–22 Based on such a strategy, several pyrazoline-core hot exciton materials were successfully fabricated and subsequently applied for OLED devices. 19 However, detailed guidelines for excited state manipulation and aggregate state properties still remain far from sufficient for implementing rational molecular design. In the current work, we systematically investigated the role of non-conjugated functional groups on fluorescence behavior and exciton dynamics based on a series of pyrazoline derivatives (Scheme 1).…”

Design, synthesis and application of tetraphenylbenzene-based blue organic electroluminescent materials with aggregation-induced emission and hot exciton properties

“…Fortunately, hot exciton materials, a new class of materials to break the limitation of 25% exciton utilization rate, which can transform the triplet state into the singlet exciton through a high-lying reverse intersystem crossing (hRISC) process and theoretically solve the problem of self-conflict between the high exciton conversion rate of T 1 → S 1 and the high exciton radiation rate of S 1 of the thermally activated delayed fluorescence (TADF) material, have unique advantages in constructing deep blue emitting materials. 18,19 Although there are many reports of deep blue hot exciton materials, their maximum external quantum efficiency is relatively low ( EQE max < 10%). 20–22 Therefore, the development of novel and efficient deep blue materials with hot exciton properties is of great significance for scientific research.…”