Executive Summary : | Pure organic emitters with thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) have numerous applications in sensors, bio-imaging, anticounterfeiting, and organic light-emitting diodes (OLEDs). Their unique ability to harness long-lived triplet excitons enhances their efficacy. In TADF, triplet excitons undergo thermal up-conversion via reverse intersystem crossing (rISC), converting to singlet excitons and harvesting 100% of internal quantum efficiency (IQE). For RTP, triplet excitons directly emit light, making purely organic emitters versatile. However, enhancing RTP necessitates converting singlet excitons to triplet excitons via ISC. To achieve efficient TADF and RTP properties in organic materials, it is essential to minimize the energy difference between excited states of lowest singlet (S1) and triplet (T1) states due to weak spin-orbit couplings (SOC) observed in purely organic materials. RTP emitters require an increased ΔEST to promote ISC over competing rISC. This proposal introduces fluorenone-based D-A-D and D-A molecules to exhibit TADF and RTP, respectively. D-A-D structured organic molecules with fluorenone as acceptors and various donor groups will exhibit TADF properties due to small ΔEST resulting from strong HOMO and LUMO overlap. The D-A moiety will have higher ΔEST due to increased electron density towards the fluorenone ring due to heavy atom effect, accelerating the ISC process and increasing triplet excitons for observing RTP. The rigid D-A molecule will also enhance RTP quantum efficiency. After achieving TADF and RTP, these novel molecules can be used for time-resolved cell imaging and anticounterfeiting, potentially leading to collaboration on OLED devices. |