White-light generation from all-solution-processed OLEDs using a benzothiazole–salophen derivative reactive to the ESIPT process
A salicylidene derivative, N,N′-bis(salicylidene)-(2-(3′,4′-diaminophenyl)benzothiazole) (BTS), reactive in the Excited State Intramolecular Proton Transfer (ESIPT) process, was synthesized and its photophysical properties were evaluated, presenting an emission covering the entire range of the visible spectrum. Due to its broad emission band, BTS was successfully tested as an active layer in solution-processed organic light-emitting diodes with white-light emission. These diodes were prepared using solution-based protocols with the dye solubilized in a poly(9-vinylcarbazole) matrix. Different guest : host (polymer : BTS) molar ratios were used to optimize the diode performance. The optimized architecture rendered the best so far all-solution-processed ESIPT OLED with a luminance of 34 cd m−2 at 13.5 V with CIE coordinates 0.31, 0.40.