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Published on: December 27, 2018
TICT, and Deep-Blue Electroluminescence from Acceptor-Donor-Acceptor Molecules
Amrutham Linet1,2, Aparna G Nair3, Simi Achankunju1,2
1Chemical Sciences and Technology Division, CSIR-NIIST, Thiruvananthapuram, Kerala, 695019, India.
Abstract:
Donor-acceptor (D-A) materials based on butterfly-shaped molecules could inhibit exciton-migration-induced quenching due to molecular twist. To explore this attribute towards beneficial photophysical properties, three novel bipolar acceptor-donor-acceptor (A-D-A) molecules with triphenyl triazine end capping along with substitution ortho to the Tröger's base (TB) scaffold varying from H, Me, and F were explored. The installation of H/Me/F imparted an electron push-pull effect with concomitant maneuvering of photophysical properties. On increasing solvent polarity, a remarkable bathochromic shift with a significant decrease in emission efficiency was observed due to the twisted intramolecular charge transfer state (TICT). Emission enhancement in the ethylene glycol-water mixture and diminution in the THF-water mixture further confirmed the existence of TICT states in these TBs. The torsional dynamics in the excited state were also evidenced by the time-dependent density-functional theory (TD-DFT) calculations. Owing to the butterfly architecture of the TB that suppressed TICT, TB-Trzs exhibited a significant blue shift, accompanied by a favorable quantum yield in the solid state. Among the three compounds, Me-TB-Trz exhibited deep-blue photoluminescence and was explored as a dopant in organic light-emitting diodes (OLEDs) to obtain deep-blue electroluminescence of brightness 4128 cdm-2 and CIE coordinates of (0.16, 0.09).
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