Rajakannu Palanisamy, an Inspire Faculty Fellow of the Department of Science and Technology (DST) along with his team has synthesized a number of new phosphorescent emitters which can help develop highly efficient Organic Light-Emitting Diodes (OLEDs) with high-efficiency.

Interest in the development of commercial display and lighting materials has been amplified due to their necessity and importance in day-to-day life. The lighting products require high efficiency and extended lifespan for success in the market. Hence, the selection of light-emitting materials in the production of commercial lighting devices is very important. These emitting materials should hold high internal quantum efficiency, short radiative lifetime, high thermal and photostability which are necessary for the fabrication of Organic Light-Emitting Diodes (OLEDs) with high efficiency.

Organic light-emitting molecules (fluorescent) are well known to harvest the excitons (photon that is absorbed by a molecule producing an excited state) only from the singlet excited states (single excited state-- where electron spins are antiparallel and spin allowed), while the phosphorescent materials (heavy-metal based complexes) tend to crop both singlet and triplet excitons (where electron spins are parallel and spin forbidden) through strong Inter-System Crossing (ISC) which can boost the Internal Quantum Efficiency (IQE) of the molecule.

Although much research has been done on visible light emitters, more work has to be done to fully understand deep-red and near-infrared emitters in order to take advantage of their intriguing applications.

Dr Palanisamy from The Gandhigram Rural Institute-Deemed University, Tamil Nadu decided to try Ir(III) and Pt(II) based visible and NIR-emitting materials which are highly suitable for OLED applications. For example pre-designed organic ligands with particular functional groups and the metal precursor (K₂PtCl₄), were used to synthesize Pt(II)-based phosphorescent emitters (mono- or di-nuclear molecules) with square planar geometry under reflux conditions (N₂ atm) in appropriate solvents. Their preparations were accepted for publication in a series of papers in Journals Journal of Molecular Structure, Journal of organometallic chemistry like. They have short radiative lifetimes, exhibit great efficiency and robust emission in the near-infrared spectrum making them better than previously reported or available ones.  These emitters were utilized for the fabrication of visible and NIR OLEDs and showed high efficiency compared to reported OLEDs.

The increasing demand for smart electronic devices in the silicon age, require efficient, safe, and sustainable OLED materials and the materials developed would certainly make a difference. They could also be bio-medical treatment and night-vision display for security purposes.

Research output:

1. Journal of Molecular Structure, 2023 (Accepted). B. Sarika, T. Keerthana, P. Vengadeshwaran, B. Shankar and P. Rajakannu*, Effect of substituents in tuning the inter-and intra-molecular interactions in the dinuclear Pt(II) complexes.
2. Journal of Organometallic Chemistry, 2023 (Accepted). B. Shankar and P. Rajakannu*, Synthesis, Characterization and Photo-physical Studies of Naphthalamide-based Ir(III) Complexes.