Stable and efficient organic light-emitting diodes were prepared using tetradentate platinum-based blue and red emitters. In one example, a series of stable and efficient red phosphorescent OLEDs was fabricated employing a phenyl-pyridyl-carbazole based tetradentate cyclometalated Pt(II) complex as an emitting dopant and utilizing a commercially available host, transporting, and blocking materials. By implementing this platinum complex in electrochemically stable device architectures, long operational lifetimes were achieved with an estimated LT97 of over 600 hrs at luminance of 1000 cd/m2.