To develop phosphorescent materials for organic light-emitting diodes (OLEDs), novel organoplatinum(II) complexes bearing oligofluorene-based cyclometalated ligands were synthesized. These materials exhibited intense reddish orange photoluminescence (PL) and thus were applied as emitting dopants to OLEDs. The fabricated OLEDs showed electroluminescence identical to PL of the corresponding dopants. A non-doped device was also successfully fabricated using the developed complex as an emitting layer.