Electroluminance based on organic small molecule is one of the most promising technologies for flat panel displays. The quantum yield of current fluorescent dyes is limited to 25% due to the limited formation of singlet excited state. Heavy metal complexes can result in high-efficiency electrophosphorescence due to strong spin-orbit coupling leading to singlet-triplet state mixing, and hence they are attracted to apply in the fabrication of organic light-emitting devices (OLED). In this article, we detail the recent developments and applications of the red, green, blue materials and the host materials in electrophosphorescent OLEDs.