A tandem organic electroluminescent device. The tandem organic electroluminescent device comprises a substrate having a pixel thin film transistor. A rib with chambered corners is formed on the substrate, surrounding a display region. A protrusion is formed in the display region. A plurality of organic light emitting diodes is stacked vertically in the display region, covering the protrusion, wherein each organic light emitting diode comprises a top electrode, an organic electroluminescent layer, and a bottom electrode. The bottom electrode of the bottommost organic light emitting diode is electrically connected to the pixel thin film transistor. A common electrode electrically connected to the top electrode of the topmost organic light emitting diode directly over the protrusion.