Bright High Spin Molecular Semiconductors

BRIGHTS builds on the proposer’s discovery of high photoluminescence quantum efficiency, PLQE, from high spin states excitons (S = 1, 3/2, 2) in molecular semiconductors. This is underpinned by their recent development of spin doublet molecular semiconductors where bright spin doublet excitons support efficient OLED operation, particularly for red and near-IR. High spin molecular systems have previously been developed for their quantum properties but have been non-luminescent, preventing optical readout. The luminescent systems developed in BRIGHTS open up new spin-exciton science and new opportunities for optical writing, manipulation and reading of spin states. The core of the project is the development of new materials systems with high spin excitons that have high PLQE. These materials developments include: (a) high PLQE in spin doublet systems, with electron acceptor substitutions and designs for near-IR emitters, used to construct: (b) systems where photogeneration evolves from spin doublet to quartet, with optimisation of intersystem and reverse intersystem crossing via engineering of charge transfer states, and new designs using TADF emitters; (c) conjugatively coupled di- and poly-radicals. For diradicals this will focus on exploring the inter-radical coupling to engineer PL in both triplet and singlet manifolds. This builds on the proposer’s discovery of red-shifted singlet exciton PL from zwitteronic charge-transfer character singlet excitons.These materials systems will be explored for applications in: (d) spin-optical applications for sensing. Optical spin pumping and optically-detected magnetic resonance, ODMR, will be explored and developed for sensing, at high and low B fields, and for possible biomedical sensing; (e) spin-controlled charge transport. FETs to study transport in field-doped radical polymers in the ‘Mott-Hubbard insulator’ regime; (f) new designs for solar cell applications with spin radicals with high PLQE.