# Carbazole–benzocarbazole fragments having derivative as very efficient host material for TADF based OLEDs

## TL;DR

This paper introduces a new host material, BCCOX, for green TADF OLEDs that improves efficiency and stability in display and lighting technologies.

## Contribution

The novel carbazole–benzocarbazole derivative BCCOX is designed and shown to be an efficient host material for TADF OLEDs.

## Key findings

- BCCOX has a decomposition onset beyond 400 °C and a glass transition temperature of ~194 °C, ensuring thermal stability.
- BCCOX achieves a maximum external quantum efficiency of 10.4% in green TADF OLEDs.
- The material enables a current efficiency of 20.6 cd A−1 and power efficiency of 12.7 lm W−1 at low voltages.

## Abstract

Organic light-emitting diodes (OLEDs) are widely adopted in modern display and lighting technologies; however, while significant progress has been achieved in the development of thermally activated delayed fluorescence (TADF) emitters, comparatively limited attention has been paid to the rational design of compatible host materials. In this work, a carbazole–benzocarbazole-based derivative, BCCOX, was designed and synthesized as an efficient host material for green TADF OLEDs. BCCOX maintains excellent thermal integrity, exhibiting a decomposition onset beyond 400 °C and a high glass transition temperature of approximately 194 °C, ensuring morphological integrity and operational reliability under device fabrication and operating conditions. The material further possesses a wide optical bandgap of 3.6 eV and favorable exciton dynamics, enabling effective exciton confinement and utilization in TADF systems. When employed as the host matrix in green TADF OLED devices, BCCOX delivers a maximum external quantum efficiency of 10.4%, along with a current efficiency of 20.6 cd A−1 and a power efficiency of 12.7 lm W−1 at relatively low driving voltages. These results demonstrate that carbazole–benzocarbazole architectures offer a robust and versatile platform for high-performance host materials, positioning BCCOX as a promising candidate for efficient, stable, and cost-effective next-generation OLED display applications.

OLEDs are widely used in displays and lighting, yet host material design for TADF systems remains limited. Here, a carbazole–benzocarbazole derivative, BCCOX, is developed as an efficient host for green TADF OLEDs.