An organic light emitting display device comprising: a substrate ; a first buffer layer disposed on the substrate, the first buffer layer comprising a first material; a first thin film transistor (T1) disposed on the first buffer layer of a display area; an organic light emitting diode (OLED) disposed on and electrically coupled with the first thin film transistor; a second thin film transistor (T2) disposed on the first buffer layer of a non-display area; and an encapsulation layer disposed over the organic light emitting diode of the display area, the second thin film transistor (T2) and the first buffer layer of the non-display area, the encapsulation layer comprising a plurality of layers, a bottom-most layer of the encapsulation layer comprising the first material, wherein at least a portion of the first buffer layer and an edge portion of the bottom-most layer of the encapsulation layer are in contact with one or more layers between the at least a portion of the first buffer layer and the edge portion of the bottom-most layer of the encapsulation layer to encapsulate the first and second thin film transistor and the organic light emitting diode (OLED), and wherein the one or more layers comprises a passivation layer (PAS) provided between the first buffer layer and the bottom-most layer of the encapsulation layer , the passivation layer (PAS) provided directly over the source electrode and drain electrode of each of the first thin film transistor (T1) and the second thin film transistor (T2) to encapsulate the first thin film transistor (T1) and the second thin film transistor (T2), the passivation layer (PAS) comprising the first material. a substrate ; a first buffer layer disposed on the substrate, the first buffer layer comprising a first material; a first thin film transistor (T1) disposed on the first buffer layer of a display area; an organic light emitting diode (OLED) disposed on and electrically coupled with the first thin film transistor; a second thin film transistor (T2) disposed on the first buffer layer of a non-display area; and an encapsulation layer disposed over the organic light emitting diode of the display area, the second thin film transistor (T2) and the first buffer layer of the non-display area, the encapsulation layer comprising a plurality of layers, a bottom-most layer of the encapsulation layer comprising the first material, wherein at least a portion of the first buffer layer and an edge portion of the bottom-most layer of the encapsulation layer are in contact with one or more layers between the at least a portion of the first buffer layer and the edge portion of the bottom-most layer of the encapsulation layer to encapsulate the first and second thin film transistor and the organic light emitting diode (OLED), and wherein the one or more layers comprises a passivation layer (PAS) provided between the first buffer layer and the bottom-most layer of the encapsulation layer , the passivation layer (PAS) provided directly over the source electrode and drain electrode of each of the first thin film transistor (T1) and the second thin film transistor (T2) to encapsulate the first thin film transistor (T1) and the second thin film transistor (T2), the passivation layer (PAS) comprising the first material. <EOS>