Achieving the Reverse Intersystem Crossing in Chalcone Based Donor-Acceptor System through Down-Conversion of Triplet Exciton

Piyush Singh; Pradip Pattanayak; Pradipta Purkayastha; Sujit Kumar Ghosh

doi:10.1002/chem.202302587

Achieving the Reverse Intersystem Crossing in Chalcone Based Donor-Acceptor System through Down-Conversion of Triplet Exciton

Chemistry. 2023 Nov 16;29(64):e202302587. doi: 10.1002/chem.202302587. Epub 2023 Oct 4.

Authors

Piyush Singh¹, Pradip Pattanayak², Pradipta Purkayastha², Sujit Kumar Ghosh¹

Affiliations

¹ Department of Chemistry, Visvesvaraya National Institute of Technology, Nagpur, 440010, Maharashtra, India.
² Department of Chemistry, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, WB, India.

PMID: 37747412
DOI: 10.1002/chem.202302587

Abstract

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 T₃ ) to lowest singlet state (S₁ ), 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).

Keywords: donor-acceptor system; reverse intersystem crossing; spin-orbit coupling; thermally activated delayed fluorescence; triplet down-conversion.