Organic electroluminescent materials and devices

An organic light emitting device (OLED) comprising, sequentially:

• an anode;
• a hole transporting layer;
• an emissive region;
• an electron transporting layer;
• and
• a cathode;
• wherein the emissive region comprises:
• a first compound;
• a second compound;
• and
• a third compound;
• wherein the first compound is capable of functioning as a phosphorescent emitter in an OLED at room temperature;
• wherein the second compound meets at least one of the following conditions:
• (1) the second compound is capable of functioning as a TADF emitter in an OLED at room temperature;
• and
• (2) the second compound is capable of forming an exciplex with the first compound in an OLED at room temperature;
• wherein the third compound is a fluorescent compound functioning as an emitter in said OLED at room temperature;
• wherein when a voltage is applied across the OLED, (i) excitons are transferred from the first compound to the second compound, which are further transferred to the third compound, or (ii) excitons are transferred from the second compound to the first compound, which are further transferred to the third compound.