The main objective of INVESTCPE is to enhance the quantum efficiency of Circularly Polarised (CP) emitters exploiting singlet-triplet inversion on specifically engineered organic dyes. To this end, the project will design, synthesise, and spectroscopically and computationally characterise a set of new chiral molecules based on the heptazine core. The recent discovery of singlet-triplet inversion in heptazine-like systems urges to bridge this phenomenon to chiral applications. This challenge can only be tackled combining expertise in chemical synthesis, (chir)optical spectroscopy, and computations. Application of these systems in Organic Light Emitting Diodes (CP-OLEDs) finds wide impact in everyday life in lighting devices and consumer displays, such as smartphones, tablets and TVs. The major challenge in this field is to increase OLEDs external quantum efficiency to obtain brighter devices with lower power consumption. The most promising designs exploit Thermally Activated Delayed Fluorescence, providing high efficiency materials without heavy elements. This process takes advantage of singlet-triplet proximity, exploiting triplet harvesting through reverse intersystem crossing. The current strategy to design delayed fluorescence dyes relies on achieving a small singlet-triplet gap, to speed up the process, through spatial separation of HOMO and LUMO, generally in donor-acceptor architectures. Extremisation of this design leads to singlet-triplet inversion, as observed in heptazine, providing even faster reverse intersystem crossing. Major advances in the field are hampered by the lack of design rules due to: (i) difficult translation of electronic features for molecules showing singlet-triplet inversion in principles to be exploited systematically by synthetic chemists (ii) low sensitivity of triplet states to fine-tuning strategies commonly used for singlet states (iii) unknown relationship between electronic properties at molecular level and external quantum efficiency in devices. INVESTCPE, closing the gap among different disciplines, will systematically tackle this subject preparing and characterising a series of new chiral dyes. Iterative and interconnected experimental and computational studies will provide the necessary tools to advance fundamental knowledge and to underpin the guidelines for rational design of new, efficient OLEDs.

Disclaimer: This project is funded by Italian Ministry of University and Research under the PRIN program – Progetti di Rilevante Interesse Nazionale (PRIN) – PRIN 2022 – PROGETTO PRIN 2022 N. 2022CXHY3A