Organic electroluminescent materials and devices

1. A composition comprising, a first compound and a second compound mixed together to form a stable evaporation source for use in a single sublimation crucible of a vacuum thermal evaporation (VTE) process;

wherein the first compound has a different chemical structure than the second compound;

wherein the mixture of the first compound and the second compound is capable of functioning as an E-type delayed fluorescent system in an organic light emitting device at room temperature;

wherein the first compound has an evaporation temperature T 1 of 150 to 350° C.;

wherein the second compound has an evaporation temperature T 2 of 150 to 350° C.;

wherein an absolute value of T 1 −T 2 is less than 20° C.;

wherein the first compound has a concentration C 1 in said mixture and a concentration C 2 in a film formed by evaporating the mixture in a vacuum deposition tool at a constant pressure between 1×10 −6 Torr to 1λ10 −9 Torr, at a 2 Å/sec deposition rate on a surface positioned at a predefined distance away from the mixture being evaporated;

wherein absolute value of (C 1 −C 2 )/C 1 is less than 5%;

wherein the first compound has the formula of D-L-A, where L is a direct bond, A is an electron acceptor group comprising a structure selected from the group consisting of:

wherein Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 , Z 7 , and Z 8 each independently comprise C or N;

wherein at least two of Z 1 , Z 2 , Z 3 , Z 4 , Z 5 , Z 6 , Z 7 , and Z 8 are N;

wherein Y 1 to Y 8 independently comprise C or N;

wherein A 1 to A 8 independently comprise C or N;

wherein J 1 and J 2 independently comprise C or N;

wherein L 1 to L 4 independently comprise C or N;

wherein X 1 is O, S, or NR 14 ;

wherein R 14 is aryl or heteroaryl,

wherein D is an electron donor group is selected from the group consisting of:

wherein the second compound (i) comprises at least one chemical group selected from the group consisting of anthracence, naphthylene, phenanthrene, triphenylene, dibenzothiophene, dibenzofuran, dibenzoselenophene, aza-triphenylene, aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene, or (ii) is selected from the group consisting of:

2. The composition of claim 1 , wherein the first compound has a vapor pressure of P 1 at T 1 at 1 atm, and the second compound has a vapor pressure of P 2 at T 2 at 1 atm; and

wherein the ratio of P 1 /P 2 is within the range of 0.90:1 to 1.10:1.

3. The composition of claim 1 , wherein the second compound is capable of functioning as a host in an organic light emitting device at room temperature.

4. The composition of claim 1 , wherein the second compound comprises at least one chemical group selected from the group consisting of anthracence, naphthylene, phenanthrene, triphenylene, dibenzothiophene, dibenzofuran, dibenzoselenophene, aza-triphenylene, aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, and aza-dibenzoselenophene.

5. The composition of claim 1 , wherein the composition further comprises a third compound, wherein the third compound has a different chemical structure than the first and second compounds, wherein the third compound has an evaporation temperature T 3 of 150 to 350° C., and wherein absolute value of T 1 -T 3 is less than 20° C.

6. The composition of claim 1 , wherein the composition is in liquid form at a temperature less than the lesser of T 1 and T 2 .

7. The composition of claim 1 , wherein the electron donor group comprises at least one chemical group selected from the group consisting of amino, indole, carbazole, benzothiophene, benzofuran, benzoselenophene, dibenzothiophene, dibenzofuran, dibenzoselenophene, and combinations thereof.

8. The composition of claim 1 , wherein the electron acceptor group is selected from the group consisting of:

9. The composition of claim 1 , wherein the donor group is selected from the group consisting of:

10. A method for fabricating an organic light emitting device comprising a first electrode, a second electrode, and a first organic layer disposed between the first electrode and the second electrode, wherein the first organic layer comprises a first composition comprising a mixture of a first compound and a second compound, the method comprising:

providing a substrate having the first electrode disposed thereon;

depositing the first organic layer over the first electrode; and

depositing the second electrode over the first organic layer, wherein the first compound has different chemical structure than the second compound,

wherein depositing the first organic layer comprises placing a composition of claim 1 in a single sublimation crucible of a vacuum thermal evaporative (VTE) process and evaporating the composition.

11. A composition comprising a first compound and a second compound mixed together to form a stable evaporation source for use in a single sublimation crucible of a vacuum thermal evaporation (VTE) process;

wherein the first compound has a different chemical structure than the second compound;

wherein the mixture of the first compound and the second compound is capable of functioning as an E-type delayed fluorescent system in an organic light emitting device at room temperature;

wherein the first compound has an evaporation temperature T 1 of 150 to 350° C.;

wherein the second compound has an evaporation temperature T 2 of 150 to 350° C.;

wherein an absolute value of T 1 -T 2 is less than 20° C.;

wherein the first compound has a concentration C 1 in said mixture and a concentration C 2 in a film formed by evaporating the mixture in a vacuum deposition tool at a constant pressure between 1×10 −6 Torr to 1λ10 −9 Torr, at a 2 Å/sec deposition rate on a surface positioned at a predefined distance away from the mixture being evaporated;

wherein the absolute value of (C 1 −C 2 )/C 1 is less than 5%;

wherein the first compound is selected from the group consisting of:

12. The composition of claim 11 , wherein the second compound is selected from the group consisting of: