TICT, and Deep‐Blue Electroluminescence from Acceptor‐Donor‐Acceptor Molecules

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). Insights into twisted intramolecular charge transfer (TICT) dynamics in the Acceptor‐Donor‐ Acceptor type materials. These compounds exhibited significant photophysical changes in solution as well as in solid state. Also, proof‐of‐concept OLED devices exploring one of the materials as an emitter exhibited deep blue electroluminescence with a brightness of 4128 cdm−2 and CIE coordinates of (0.16, 0.09).