Simultaneous enhancement of the carrier mobility and luminous efficiency through thermal annealing a molecular glass material and device

Abstract

The molecule 2,5,2′,5′-tetrakis(2,2-diphenylvinyl)biphenyl (TDPVBi) shows excellent solubility in organic solvents, a fully amorphous (glass state) property and strong blue emission in the solid state, endowing it with potential to fabricate solution-processed small-molecular devices. To further improve the quality of TDPVBi films, thermal annealing of method was performed for the pristine films, as prepared from solution, and proved to be an efficient way to repair the defects (e.g. pinhole) that exist in the pristine films. It is found that the films tend to become compact with level surface morphology after thermal annealing at a temperature around their glass transition temperature (T_g). The device characteristics show that thermal annealing induces a simultaneous enhancement of the hole mobility and luminous efficiency. The luminous efficiency reaches 4.60 cd A⁻¹ (corresponding external quantum efficiency of ∼3.0%) after thermal annealing at a temperature of 120 °C, which is double that of the device without annealing.