Evolution of Color-tunable TADF Emitters in OLEDs: From Design Strategy to Color Modulation

Abstract

Organic thermally activated delayed fluorescence (TADF) materials have gained abundant attention in recent times specifically in advancing organic light-emitting diodes (OLEDs) due to the possibility to achieve 100% EQE and ability to tune emission color. Several design strategies have been developed for the precise control of the singlet–triplet energy gap (ΔEST) and RISC process, enabling continuous improvement in both color tunability and device efficacy. This review presents a careful overview of how TADF emitter design strategies have evolved to achieve better color control and device performance in OLEDs. We discuss the evolution from early donor-acceptor (D–A) molecular designs to more advanced methodologies, such as adjusting molecular conjugation, incorporating steric effects and substituents to alter emission wavelengths. The development of TSCT and multi-resonance TADF systems is emphasized for their impact on achieving purer and more tunable colors. In the later part, we summarize the progression from the early conceptual development to the emergence of recent blue, green, red, and white TADF OLEDs. Thus, the objective of this review is to further the design strategy for achieving next-generation TADF materials for high-performance, color-tunable OLED applications.