Considerable improvement in the stability of solution processed small molecule OLED by annealing

► We studied the annealing effect on solution processed small molecule organic films. ► The densities of the spin-coated films increased as the annealing temperature rose. ► The surface roughness decreased as the annealing temperature rose. ► Corresponding wet OLEDs' stabilities are equivalent to the vacuum counterparts. ► Annealing process plays a key role in prolonging the stability of spin-coated OLED.