An organic light-emitting device comprising a transparent substrate, an anode layer, a cathode layer, organic functional layers sandwiched between the anode layer and the cathode layer, and an encapsulation layer fabricated on one side or both sides of the device, wherein the encapsulation layer includes a thin multilayer structure and a thick organic insulation layer. The thin multilayer structure has a period number (n) of alternating layers formed of a polymer material layer and a ceramic material layer. The thick organic insulation layer is made up of polymer materials on top of the thin multilayer.