Inexpensive and valuable: a series of new luminogenic molecules with the tetraphenylethene core having excellent aggregation induced emission properties

Abstract

One of the obstructive problems of luminogenic molecules is aggregation caused quenching (ACQ) and as a result they lose their emissive property when they turn into a solid from their solution form. Therefore, there is an increase in the demand for molecules having the aggregation induced emission (AIE) property, the opposite of ACQ. Bright and new luminogenic molecules, tetraphenylethene (TPE) core anchored by indole (TIPE), tert-butylcarbazole (TTBCPE) and tetrahydrocarbazole (TDCPE), were synthesized practically in two steps without any expensive boronic acids or Pd catalysts and show high thermal stabilities and excellent aggregation induced emission properties. The compounds exhibit thermal degradations not lower than 467 °C and up to 516 °C. All three luminogens are AIE-active and show an increase in the fluorescence intensity up to 175-fold. The time-resolved emission decay studies show two relaxation pathways in a THF–water mixture (10–90%) for all three compounds. Non-doped turquoise and light green OLED devices using TIPE, TTBCPE and TDCPE as a light-emitting layer exhibit a maximum brightness of up to 18 000 cd m⁻², maximum current efficiencies up to 7.7 cd A⁻¹, low turn-on voltages between 5.0 and 9.0 V and with external quantum efficiencies of up to 3.2. The preferred synthetic method is suitable for an adding electron-donating or -withdrawing substituents to make very efficient OLED devices.