Pendant Substitution of a Functionalized Benzothiadiazole-Based Single Polymer for White Organic Light-Emitting Diodes

Abstract

White-light-emitting polymer materials have attracted considerable interest due to their remarkable flexibility, low-cost device manufacturability, and strong thermal resilience. However, generating a dual-mode white-light emission in a single molecular core is highly challenging. In this study, we developed and synthesized a molecular core comprising electron-donating triphenylamine in the main chain and functionalized benzothiazole as an electron-withdrawing core at the pendent position, named (Z)-2-(benzo(c)(1,2,5)thiadiazol-5-yl)-3-(4-(bis(4-bromo phenyl)amino)phenyl)acrylonitrile (TPABTZ). TPABTZ exhibited yellow emission, which is copolymerized with blue-emitting 9,9 '-dihexylfluorene (DHF) in different compositions to accomplish polymer-based pure white-light emission. Significantly, the copolymer with P-TPABTZ 0.5 (0.5% of TPABTZ in the polymer backbone) exhibited efficient white-light emission in both photoluminescence (PL) and electroluminescence (EL). P-TPABTZ 0.5 exhibited a dual-band white-light emission with CIE color coordinates and obtained a maximum EQE of (0.34, 0.30) and 4.23%, respectively. Moreover, the attained maximum current, power, and luminance efficiencies are 3.8 cd A-1, 4.3 lm W-1, and 10250 cd m-2, respectively. The other copolymers of P-TPABTZ 25, P-TPABTZ 10, and P-TPABTZ 5.0 validate enhanced EL performance and PL quantum yield in both solution and thin films. This effect can be ascribed to the well-ordered supramolecular circular domains organized at the surface level. The above findings validate the materials engineering approaches in efficient WOLEDs and pave the way to advance in future lighting and display applications.