Acceptor-donor-acceptor based thermally activated delayed fluorescent materials: structure-property insights and electroluminescence performances

Organic light-emitting diodes (OLEDs) have transformed the display and lighting industries with their high electroluminescence, flexibility, and tunable colors. After fluorescent and phosphorescent materials, thermally activated delayed fluorescence (TADF) materials have emerged as low-cost emitters to enhance OLED performances efficiently by harvesting both singlet and triplet excitons and converting them into light emission. Among the developed conventional TADF materials, there has been intense research with different classes, such as D-A, D-A-D, and D-pi-A. However, recently, a new class states that Acceptor-Donor-Acceptor (ADA) molecules, known for their efficient charge-transfer nature, have exhibited significant potential as prominent TADF emitters for high electroluminescent OLEDs. However, there is no clear understanding of their structural insights for ADA-based TADF materials. So there needs to be a comprehensive understanding of the aspect of the molecular design and structure-property relationship. To fill this gap, we presented a comprehensive, in-depth review of ADA-based TADF materials, encompassing their molecular design principles, photo-physical mechanisms, device architectures, and current challenges faced in this era. Finally, the future perspective of this class of materials in forthcoming highly efficient OLED displays is also discussed. Thermally activated delayed fluorescent (TADF) materials shown great attention in Organic light-emitting diodes (OLEDs). Herein, we have systematically reviewed the Acceptor-Donor-Acceptor based TADF materials with electroluminescent characteristics.