Carbazole-based gumbos for highly efficient blue OLEDs
Various examples are provided for carbazole-based GUMBOS (group of uniform materials based on organic salts), and its application in organic light emitting diodes (OLEDs). In one example, a composition includes a solid phase carbazole-based GUMBOS (group of uniform materials based on organic salts) comprising a counterion such as, e.g., trifluoromethanesulfonate ([Otf]), bis-(trifluoromethanesulfonyl)imide ([NTf 2 ]), bis-(pentafluoroethylsulfonyl)imide ([BETI]), tetrafluoroborate (BF4), hexafluorophosphate (PF6), and/or thiocyanate (SCN). The carbazole-based GUMBOS can include carbazoleimidazole-based GUMBOS or 3,6-diBDC carbazolium-based GUMBOS. In another example, a method includes preparing a biphasic solution; separating a layer of DCM from the biphasic solution after stirring; washing the DCM with water to remove byproducts; and evaporating the DCM to form a solid phase carbazoleimidazole-based GUMBOS. Preparing the biphasic solution can include carbazoleimidazolium iodide (CM) dissolved in dichloromethane (DCM) and a dissolved salt including a sodium salt or a lithium salt.
1. A composition, comprising:
a solid phase carbazole-based GUMBOS (group of uniform materials based on organic salts) comprising a carbazole-based counterion.
2. The composition of claim 1 , wherein the carbazole-based counterion is selected from the group consisting of trifluoromethanesulfonate ([OTf]), bis-(trifluoromethanesulfonyl)imide ([NTf 2 ]), bis-(pentafluoroethylsulfonyl)imide ([BETI]), tetrafluoroborate (BF4), hexafluorophosphate (PF6), and thiocyanate (SCN).
3. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS comprises an imidazole group or (alkyl)imidazole group at a 3-, 6-, or N-position of a carbazole unit.
4. The composition of claim 3 , wherein the (alkyl)imidazole group is a (methyl) imidazole group at the 3-position of the carbazole unit.
5. The composition of claim 3 , wherein the imidazole group is at the 3-position of the carbazole unit.
6. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS has a fluorescence quantum yield of about 73% or greater.
7. The composition of claim 6 , wherein the solid phase carbazole-based GUMBOS has a fluorescence quantum yield of about 94% or greater.
8. The composition of claim 7 , wherein the solid phase carbazole-based GUMBOS has a fluorescence quantum yield of about 99% or greater.
9. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS has a thermal decomposition temperature (Td) in a range from about 350° C. to about 450° C.
10. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS comprises carbazoleimidazolium trifluoromethanesulfonate [CI][OTf], carbazoleimidazolium bis-(trifluoromethylsulfonyl)imide [CI][NTf 2 ], or carbazoleimidazolium bis(pentafluoroethylsulfonyl)imide [CI][BETI].
11. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS comprises 3,6-diBDC carbazolium trifluoromethanesulfonate [BDCC OTf], 3,6-diBDC carbazolium bis-(trifluoromethylsulfonyl)imide [BDCC NTf 2 ], or 3,6-diBDC carbazolium bis(pentafluoroethylsulfonyl)imide [BDCC BETI].
12. The composition of claim 1 , wherein the solid phase carbazole-based GUMBOS exhibits radiative emission from a second excited singlet state.
13. The composition of claim 12 , wherein the solid phase carbazole-based GUMBOS further exhibits radiative emission from a first excited singlet state.
14. The composition of claim 12 , wherein an energy gap between a first excited singlet state of the solid phase carbazole-based GUMBOS and the second excited singlet state is greater than 6000 cm −1 .
15. An organic light emitting diode (OLED), comprising an active layer including the solid phase carbazole-based GUMBOS of claim 1 .
16. The OLED of claim 15 , wherein the active layer is disposed between a first electrode and a second electrode.
17. The OLED of claim 16 , wherein the active layer comprises a GUMBOS emission layer and an electron transport layer.
18. A method, comprising:
preparing a biphasic solution comprising carbazoleimidazolium iodide (CII) dissolved in dichloromethane (DCM) and a dissolved salt comprising a sodium salt or a lithium salt;
separating a layer of DCM from the biphasic solution after stirring;
washing the DCM with water to remove byproducts; and
evaporating the DCM to form a solid phase carbazoleimidazole-based GUMBOS (group of uniform materials based on organic salts).
19. The method of claim 18 , wherein the dissolved salt comprises sodium trifluoromethanesulfonate (NaOTf) dissolved in deionized water.
20. The method of claim 19 , wherein the solid phase carbazoleimidazole-based GUMBOS comprises carbazoleimidazolium trifluoromethanesulfonate [CI][OTf].
21. The method of claim 18 , wherein the dissolved salt comprises lithium bis(trifluoromethylsulfonyl)imide (LiNTf 2 ) or lithium bis-(pentafluoroethylsulfonyl)imide (LiBETI) dissolved in deionized water.
22. The method of claim 21 , wherein the solid phase carbazoleimidazole-based GUMBOS comprises carbazoleimidazolium bis-(trifluoromethylsulfonyl)imide [CI][NTf 2 ] or carbazoleimidazolium bis(pentafluoroethylsulfonyl)imide [CI][BETI].
23. The method of claim 18 , wherein the solid phase carbazoleimidazole-based GUMBOS is based upon anion exchange of N-Ethylhexyl-3-imidazolium carbazole.
24. The method of claim 18 , wherein the biphasic solution was stirred for 3-4 days.
25. The method of claim 18 , further comprising freeze drying the solid phase carbazoleimidazole-based GUMBOS.