WHITE LIGHT EMISSION

Abstract

The present invention relates inter alia to compositions comprising conjugated polymers and a small molecule, devices comprising the composition and the application of the devices.

Claims

1. Composition comprising a first conjugated polymer and at least one phosphorescent small molecule emitter, wherein the concentration of the phosphorescent small molecule emitter is below 4 wt.-% with respect to the total mass of the composition.

2. Composition according to claim 1, further comprising a second conjugated polymer that is different from the first conjugated polymer.

3. Composition according to claim 2, wherein the first and the second conjugated polymers are fluorescent polymers.

4. Composition according to claim 1, wherein .sub.phos.sup.PL>.sub.cP1.sup.PL, wherein .sub.phos.sup.PL and .sub.phos.sup.PL and .sub.cP1.sup.PL are the peak photoluminescent emission wavelengths of the phosphorescent small molecule emitter and the first conjugated polymer, respectively.

5. Composition according to claim 2, wherein .sub.phos.sup.PL>.sub.cP2.sup.PL, .sub.phos.sup.PL>.sub.cP1.sup.PL, and .sub.cP1.sup.PL.sub.cP2.sup.PL, wherein .sub.phos.sup.PL, .sub.cP2.sup.PL and .sub.cP1.sup.PL are the peak photoluminescent emission wavelengths of the phosphorescent small molecule emitter, the second conjugated polymer and the first conjugated polymer, respectively.

6. Composition according to claim 4, wherein .sub.phos.sup.PL and .sub.cP12.sup.PL represent complementary colors, wherein .sub.cP12.sup.PL is defined by the peak photoluminescent emission wavelength of a composition of the first conjugated polymer and the second conjugated polymer.

7. Composition according claim 1, wherein the first conjugated polymer emits blue light.

8. Composition according to claim 2, wherein the second conjugated polymer emits yellow light.

9. Composition according to claim 2, wherein the second conjugated polymer emits green light.

10. Composition according to claim 2, wherein the first and the second conjugated polymers are selected from arylamines, heteroarylamines, spirobifluorenes, fluorenes or polyarylvinylenes,

11. Composition according to claim 1, wherein the phosphorescent emitter is a transition metal complex comprising a transition metal selected from the group consisting of iridium, rhodium, ruthenium, osmium, platinum, and palladium.

12. Composition according to claim 1, wherein the phosphorescent small molecule emitter is present at a concentration of less than 2 wt-%, with respect to the total mass of the composition.

13. Composition according to claim 4, wherein 570 nm<.sub.phos.sup.PL<700 nm.

14. Composition according to claim 6, wherein 490 nm<.sub.cP12.sup.PL<580 nm.

15. Composition according to claim 6, wherein 380 nm<.sub.cP12.sup.PL<550 nm.

16. Composition according to claim 2, further comprising a host that is another conjugated polymer.

17. Composition according to claim 2, further comprising an electrolyte.

18. Formulation comprising at least one composition according to claim 2 and at least one solvent.

19. (canceled)

20. (canceled)

21. Organic electroluminescent device comprising at least one composition according to claim 2, wherein the device emits white light.

22. Device according to claim 21, wherein the device is an organic light emitting diode (OLED).

23. Organic light emitting electrochemical cell (OLEC, LEEC, LEC) comprising at least one composition according to claim 2.

24. (canceled)

25. Device according to claim 21, wherein the emitted white light exhibits a CIE coordinate in a range between (0.25/0.25) and (0.4/0.47).

26. Device according to claim 25, wherein the emitted white light includes a color rendering index (CRI) of 60 or above.

27. Process for the preparation of a device according to claim 21, wherein at least one layer is either formed by vapor deposition or from solution.

Description

[0146] The invention is explained in greater detail by the following examples and drawings without wishing it to be restricted thereby.

[0147] FIG. 1 shows electroluminescent emission intensity as a function the wavelength for two different compositions used in OLECs. The device emits white light if the concentration of the phosphorescent red emitter (RE1) is 0.5 wt.-%. The device emits red light if the concentration RE1 is 5 wt.-%

WORKING EXAMPLES

Example 1

[0148] Materials and Preparation of Conjugated Polymers

[0149] RE1 is a red light emitting phosphorescent small molecule emitter as disclosed in WO 2011/141120 A1

##STR00003##

[0150] Conjugated Polymer 1 (P1)

##STR00004##

[0151] P1 can be prepared according to WO 97/39045, WO 2003/020790, WO 2005/014688 using Suzuki coupling (WO 2003/048225).

[0152] Conjugated Polymer 2 (P2)

##STR00005##

wherein, m=0.5, n=0.35 and o=0.15. P2 can be prepared according to WO 98/27136, WO 99/24526, WO 98/25874.

[0153] Conjugated Polymer 3 (P3)

##STR00006##

[0154] P3 can be prepared according to WO 97/39045, WO 2003/020790, WO 2005/014688 using Suzuki coupling (WO 2003/048225).

[0155] The ion-transport material hydroxyl-endcapped trimethylolpropane ethoxylate (TMPE) and the salt LiCF.sub.3SO.sub.3 can be purchased from Aldrich (Steinheim, FRG). The salt is dried in a vacuum oven at T=473 K before use.

[0156] All materials are dissolved separately in anhydrous tetrahydrofuran at a concentration of 10 mg/ml. The active material solutions are prepared by mixing the master solutions in a volume ratio. The active material solutions are stirred on a magnetic hot plate for 5 h at T=323 K immediately before film fabrication.

Example 2

[0157] Preparation of White Light Emitting OLEDs

[0158] For the OLED fabrication, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS, Clevios P VP AI 4083, Heraeus, FRG) is spin coated on top of carefully cleaned indium-tin-oxide (ITO) coated glass substrates (1.51.5 cm.sup.2, 20 ohms/square, Thin Film Devices, USA) at 4000 rpm for 60 s. The resulting 40 nm thick PEDOT:PSS film is dried at T=120 C. for 6 h. The active material is spin-coated from an active material solution at 2000 rpm for 60 s on top of the PEDOT:PSS layer. The resulting 120 nm thick active material is dried at T=50 C. for >5 h. The Ca cathodes (thickness: 20 nm), with an Al capping layer (thickness: 100 nm), are deposited on top of the active layer by thermal evaporation to complete the OLED structure.

[0159] Preparation of OLED1

[0160] According to the aforementioned method OLED1 having the following structure is prepared: ITO/PEDOT:PSS/P1:P2 (1.5 wt.-%):RE1 (0.8 wt.-%)/Ca/Al

[0161] Preparation of OLED2

[0162] According to the aforementioned method OLED2 having the following structure is prepared: ITO/PEDOT:PSS/P1: RE1 (0.5 wt.-%)/Ca/Al

Example 3

[0163] Preparation of White Light Emitting OLECs

[0164] For the OLEC fabrication, poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS, Clevios P VP AI 4083, Heraeus, FRG) is spin coated on top of carefully cleaned indium-tin-oxide (ITO) coated glass substrates (1.51.5 cm.sup.2, 20 ohms/square, Thin Film Devices, USA) at 4000 rpm for 60 s. The resulting 40 nm thick PEDOT:PSS film is dried at T=120 C. for 6 h. The active material is spin-coated from an active material solution at 2000 rpm for 60 s on top of the PEDOT:PSS layer. The resulting 120 nm thick active material is dried at T=50 C. for 5 h. Al cathodes (thickness: 100 nm) are deposited by thermal evaporation at p<210.sup.4 Pa through a shadow mask to complete the OLEC structure.

[0165] Preparation of OLEC1

[0166] According to the aforementioned method OLEC1 having the following structure is prepared, wherein the mass ration of P1:P3:P2:RE1 is 100:1:1.5:1: ITO/PEDOT:PSS/P1:P3 (1.0 wt.-%):P2 (1.5 wt.-%):RE1 (1.0 wt.-%):Electrolyte/Al

[0167] wherein the electrolyte is TMPE (10.0 wt.-%): LiCF.sub.3SO.sub.3 (3.0 wt.-%) and wherein in this example and in the following examples the weight percent are related to the total mass of the layer.

[0168] Preparation of OLEC2

[0169] According to the aforementioned method OLEC2 having the following structure is prepared: ITO/PEDOT:PSS/P1:RE1 (0.5 wt.-%):Electrolyte/Al wherein the electrolyte is TMPE (10.0 wt.-%): LiCF.sub.3SO.sub.3 (3.0 wt.-%)

[0170] Preparation of OLEC3

[0171] According to the aforementioned method OLEC3 having the following structure is prepared: ITO/PEDOT:PSS/P1:P2 (1.5 wt.-%):RE1 (0.8 wt.-%): Electrolyte/Al

[0172] wherein the electrolyte is TMPE (10 wt.-%): LiCF.sub.3SO.sub.3 (3 wt.-%)

[0173] Preparation of OLEC4

[0174] According to the aforementioned method OLEC4 having the following structure is prepared: ITO/PEDOT:PSS/P1:P3 (1.0 wt.-%):RE1 (0.6 wt.-%):Electrolyte/Al

[0175] wherein the electrolyte is TMPE (10 wt.-%): LiCF.sub.3SO.sub.3 (3 wt.-%)

Example 5

[0176] Preparation of a Comparative OLEC (cOLEC)

[0177] A comparative OLEC (cOLEC) is prepared in analogy to OLEC2, but with 5 wt.-% RE1 instead of 0.5 wt.-% RE1. The result is shown in FIG. 1. cOLEC emits red light, whereas OLEC2 shows white light emission.

Example 6

[0178] Characterization of Devices

[0179] The devices are driven and measured by a Keithley 2400 source-meter unit. The luminance is measured using a calibrated photodiode equipped with an eye response filter (Hamamatsu Photonics) and connected though a current-to-voltage amplifier to a HP 34401A voltmeter. Electroluminescence (EL) measurements are performed using a calibrated USB2000 fibre optic spectrometer (Ocean Optics). The colour rendering index (CRI), the CIE coordinates, and the correlated colour temperature (CCT) are calculated using the SpectraWin software. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Turn on V Max. Max Life- CIE CCT (>1 cd/ CE PE time Device (x/y) CRI (K) m.sup.2)* [cd/A] [lm/W] [h] OLED1 (0.37/0.45) 79 4500 3.7 2.6 1.2 OLED2 (0.32/0.33) 64 6000 4.4 1.6 0.64 OLEC1 (0.37/0.45) 79 4500 4.3 2.8 12 OLEC2 (0.33/0.36) 66 4800 3.6 1.5 10 OLEC3 (0.37/0.45) 77 4000 4.1 1.7 10 OLEC4 (0.39/0.46) 58 3500 2.9 1.2 8 CE: current efficacy; PE: power efficacy

[0180] As clearly shown in Table 1 mixtures of conjugated polymers and of a phosphorescent small molecule result in devices with excellent CRIs. Compositions comprising only one conjugated polymer and a phosphorescent small molecule result in devices having almost perfect white emission (0.33/0.33).