Optoelectronic Characterization of tunable Luminescent Organic Molecules

Luminescent organic molecules (LOMs) combine the photo-induced charge carrier generation and recombination of inorganic semiconductors with the lightweight and easy fabrication techniques common to organic materials. We present results of a novel class of LOMs, Benzoyl Pyraziniums, whose optical properties can be controlled by tuning the electronic and chemical structure, excitation energy, and their concentration and interaction with surrounding materials. Optical characterization of different salts of the LOMs showed increase in PL intensity, blue shift in emission spectra, and increase in recombination lifetimes with decreasing concentration. As pyridiniums are capable of intramolecular charge transfer, assuming that the primary concentration dependent non-radiative decay is through the same, this behavior can be explained by variation in the number of non-radiative decay pathways with concentration. Cumulative emission studies in solid state, to study their behavior as composites in the mesoscale regime, showed spectral blue shift in the order of just a few nanometers over the entire range of 0.1 – 100 mM but with significantly narrowed emission. Further investigations of the electrochemistry of these molecules offer unique perspectives on the charge transfer properties within them, which is used to optimize their optical emission.

This work was supported with funding from: NSF-CREST: Center for Cellular and Biomolecular Machines at UC Merced (HRD-1547848 and 2112675)