Solution-processable donor-π-acceptor type thieno[3,2-b]thiophene derivatives; synthesis, photophysical properties and applications

Two novel donor-π-acceptor (D-π-A)-type pull-push materials, M1 and M2, having triphenylamine as a donor and dimesitylboron as an acceptor, linked through a thieno[3,2-b]thiophene (TT) π-conjugated spacer bearing different functional substituents, such as -PhCN and -Ph, were synthesized and fabricated via a solution process for OLED applications. They exhibited mega Stokes shifts of 120 nm and emissions both in the solid-state and in solution. The monomers M1 and M2 had strong intramolecular charge-transfer behaviors; the solid-state quantum yields were recorded to be 76 and 72% and the solution quantum efficiencies were determined to be 100 and 95%, respectively. The solution-processed OLEDs were fabricated using low turn-on voltages, which had performances with maximum power, current and external quantum efficiencies of around 8 lm W⁻¹, 14.1 cd A⁻¹ and 4.78%, respectively, displaying emission colors from blue to green and yellowish green. The materials had strong fluorescence emission colors between yellowish and bluish under UV irradiation.