The stability of organic light-emitting devices with a spin-coated film of 4,4',4 ''-tris(3-methylphenyl-phenylamino) triphenylamine (m-MTDATA) as hole-injection layer (HIL) was investigated. The lifetime of this device is increased to 40 900 h (with an initial luminance of 100 cd/m(2)), which is 2.7 times as large as that of the control device with a vacuum-deposited film of m-MTDATA as HIL. A significant feature with this method is that the performance and the operational stability of the device with spin-coated HIL are little attenuated by the rough substrate coated by the indium-tin oxide film. The surface morphology of the solution-processed m-MTDATA thin film is quite even and uniform, and it acts as a smoothing layer in the device, which leads to the stability enhancement of the device. (C) 2009 Elsevier B. V. All rights reserved.