Array substrate for organic electroluminescent device

An array substrate for an organic electroluminescent device, comprising:

• a substrate including a pixel region;
• first and second gate electrodes on the substrate;
• first and second gate insulating layers on the first and second gate electrodes, respectively;
• first and second active layers on the first and second gate insulating layers, respectively;
• an interlayer insulating layer on the first and second active layers and including first to fourth active contact holes, the first and second active contact holes respectively exposing both sides of the first active layer, the third and fourth active contact holes respectively exposing both sides of the second active layer;
• first and second ohmic contact layers respectively contacting the both sides of the first active layer through the first and second active contact holes;
• third and fourth ohmic contact layers respectively contacting the both sides of the second active layer through the third and fourth active contact holes;
• first and second source electrodes on the first and third ohmic contact layers, respectively;
• first and second drain electrodes on the second and fourth ohmic contact layers, respectively, the first drain electrode electrically connected to the second gate electrode;
• a data line on the interlayer insulating layer and connected to the first source electrode;
• a first power line parallel to the data line and connected to the second source electrode;
• a first passivation layer on the first and second source electrodes, the first and second drain electrodes and the data line and including a first gate contact hole exposing the first gate electrode;
• a gate line on the first passivation layer and contacting the first gate electrode through the first gate contact hole, the gate line crossing the data line to define the pixel region;
• a second passivation layer on the gate line, the second passivation layer and the first passivation layer including a first drain contact hole exposing the second drain electrode;
• a pixel electrode in the pixel region and on the second passivation layer, the pixel electrode contacting the second drain electrode through the first drain contact hole;
• an organic luminescent layer on the pixel electrode and in the pixel region;
• and
• a reference electrode on the organic luminescent layer and covering an entire of the substrate,
• wherein portions of the pixel electrodes respectively contacting the organic luminescent layers in one pixel region and in another one pixel region have different heights from the substrate.