An organic electroluminescent device includes first and second substrates facing and spaced apart from each other; a gate line on an inner surface of the first substrate; a semiconductor layer over the gate line, the semiconductor layer overlying a surface of the first substrate; a data line crossing the gate line; a data ohmic contact layer under the data line, the data ohmic contact layer having the same shape as the data line; a power line parallel to, or substantially parallel to, and spaced apart from the data line, the power line including the same material as the gate line; a switching thin film transistor connected to the gate line and the data line, the switching thin film transistor using the semiconductor layer as a switching active layer; a driving thin film transistor connected to the switching thin film transistor and the power line, the driving thin film transistor using the semiconductor layer as a driving active layer; a connection pattern connected to the driving thin film transistor, the connection pattern including a conductive polymeric material; a first electrode on an inner surface of the second substrate; an organic electroluminescent layer on the first electrode; and a second electrode on the organic electroluminescent layer, the second electrode contacting the connection pattern.