Singh Piyush, Pattanayak Pradip, Purkayastha Pradipta, Kumar Ghosh Sujit
Department of Chemistry, Visvesvaraya National Institute of Technology, Nagpur, 440010, Maharashtra, India.
Department of Chemistry, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, WB, India.
Chemistry. 2023 Nov 16;29(64):e202302587. doi: 10.1002/chem.202302587. Epub 2023 Oct 4.
In recent years, understanding the mechanism of thermally activated delayed fluorescence (TADF) has become the primary choice for designing high-efficiency, low-cost, metal-free organic light emitting diodes (OLEDs). Herein, we propose a strategically designed chalcone based donor-acceptor system, where intensification of delayed fluorescence with decrease in temperature (300 K to 100 K) is observed; the theoretical investigations of electronic states and orbital characters uncovered a new cold rISC pathway in donor-acceptor system, where rISC occurs through the down-conversation of higher triplet exciton (from T ) to lowest singlet state (S ), having negative energy splitting, thus no thermal energy is required. The comprehensive research described herein might open-up new avenues in donor-acceptor system over the conventional up-convention of triplet exciton and demonstrates that not necessarily all delayed fluorescence are thermally activated (TADF).
