Emission in the Biological Window from AIE-Based Carbazole-Substituted\nFuran-Based Compounds for Organic Light-Emitting Diodes and Random\nLasers

The emission quenching\nobserved in devices utilizing luminescent\nmaterials such as solid thin films is a prevalent issue. Consequently,\nsearching for new organic luminescent compounds exhibiting aggregation-induced\nemission (AIE) behavior and characterized by relatively simple and\ncost-effective synthesis is of crucial interest among applications\nfrom optoelectronics and organic lasing branches. Herein, we report\nthe optical properties of three furan-based carbazole-substituted\ncompounds, namely, tBuCBzSO<sub>2</sub>Ph, tBuCBzSPh, and tBuCbzTCF,\nexhibiting the aforementioned AIE phenomenon. The optical properties\nof dyes were determined in classical spectroscopic experiments supported\nby quantum-chemical calculations. The thermal investigations and electrochemical\nproperties of dyes were performed to verify their usefulness in the\nconstruction of organic light-emitting diodes (OLEDs). In pursuit\nof this objective, OLEDs with a different design were fabricated,\nand their performance was subject to evaluation. In more detail, the\ndifferent design strategies relying on the utilization of neat-dye\nfilms, as well as the preparation of dye-doped poly(9-vinylcarbazole):2-(4-<i>tert</i>-butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole (PVK:PBD)\nmatrices were examined. The analysis that was conducted indicated\nthe superior potential of tBuCBzSPh for optoelectronic applications.\nNotably, the positive impact of the AIE effect on the emission of\nthe OLEDs and the ability to establish the lasing phenomenon in asymmetric,\npoly(methyl methacrylate) (PMMA)-doped polymeric slab waveguides were\nverified. The study showed that the combination of the strong intramolecular\ncharge transfer (ICT) effect with dye aggregation enables the tuning\nof the emission of the OLED toward the first biological window, making\nexamined dyes promising candidates for biomedical purposes. The same\noptical region can be attained for laser emission at relatively low\npumping conditions, reaching as low as 7.3 kW of optical power for\nthe tBuCBzSO<sub>2</sub>Ph compound.