Red/deep-red fluorophores based on benzo[1,2-b:4,5-b′]dithiophene 1,1,5,5-tetraoxide for high-performance solution-processed OLEDs

Abstract

Red organic light-emitting diodes (OLEDs) are of great significance for medical and optoelectronic fields. The development of highly efficient red organic luminescent materials, particularly those featuring donor–acceptor frameworks with narrow energy gaps, in solution-processable OLEDs is in urgent demand but extremely scarce. Herein, a series of red/deep-red organic luminescent materials based on electron-withdrawing benzo[1,2-b:4,5-b′]dithiophene 1,1,5,5-tetraoxide (BDTO) and various electron-donating groups was synthesized, and the single crystal, thermal stability, photophysical property and electronic structure of these materials were systematically investigated. They exhibited red photoluminescence (PL) peaks at 640, 666, 589 and 612 nm with satisfactory quantum yields of 37.40%, 21.50%, 42.10% and 43.30% in the solid state, respectively. Remarkably, non-doped solution-processed OLEDs fabricated with TPE-BDTO and Flu-BDTO exhibited the maximum luminescence (L_max) of 13 919 and 8076 cd m⁻², respectively. Moreover, doped solution-processed OLEDs fabricated with Flu-BDTO demonstrated a low turn-on voltage (V_on) of 3.0 V, a noticeable L_max of 13 092 cd m⁻², and an outstanding external quantum efficiency (EQE) of 5.83% as well as power efficiency of up to 2.22 lm W⁻¹. These results demonstrate that the great potential of the reported design strategy to achieve high-performance solution-processed red OLEDs.