Organic electroluminescent materials and devices

A method for fabricating an organic light emitting device (OLED), the method comprising:

• providing a substrate having a first electrode disposed thereon;
• depositing a first organic layer over the first electrode by evaporating a composition comprising a mixture of a compound W1 and a compound W2;
• and
• depositing a second electrode over the first organic layer,
• wherein the compound W1 and the compound W2 are differently selected from the group consisting of:
• (1) a first compound (S1), which is a phosphorescent material capable of functioning as a phosphorescent emitter in an OLED at room temperature;
• (2) a second compound (A1), which is a fluorescent material capable of functioning as a fluorescent emitter in an OLED at room temperature;
• and
• (3) a third compound (H1), which is a host material capable of functioning as a host in an OLED at room temperature;
• wherein at least one of the first compound S1, the second compound A1 or the third compound H1 comprises at least one substituent R*;
• wherein the compound W1 has an evaporation temperature T1 of 150 to 450° C.;
• wherein the compound W2 has an evaporation temperature T2 of 150 to 450° C.;
• wherein absolute value of T1-T2 is less than 20° C.