RU2532565C2 - Multilayer electroluminescent device - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is related to the area of electroluminescent devices - organic light-emitting diodes used as effective and highly economical solid-state sources of lighting. The electroluminescent device includes hole injection layer, hole transport layer, active luminescent layer based on electroluminescent compound of bis[2-(2'-tosylaminophenyl) benzoxazolato]zinc(2+) formula I, hole blocking layer, electron transport layer, electron injection layer and electron blocking layer with use of N,N'-bis(3-methylphebyl)-N,N'-bi(phenyl)-9,9-spirobifluorene.

EFFECT: invention allows increase in brightness of green emission of electroluminescent devices against the known level with luminescent layer based on zinc chelate complexes with salicylic aldehyde derivatives with different amines.

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Description

The invention relates to the field of creating electroluminescent devices - organic light emitting diodes, known as OLED or OLED - Organic Light Emitting Diodes - which are used as efficient and highly economical solid state lighting sources of a new generation.

Known electroluminescent device based on a complex of zinc and a derivative of N, N ¹ bis (2-hydroxybenzylidene) -1,2-phenylenediamine, containing an electron-injecting layer, a hole-injecting layer and an active luminescent layer based on the above zinc chelate complex (RF patent No. 2140956 C09K 11/06, 1999). The device emits in the green region, has a brightness of 480 kD / m ² at a voltage of 11.8 V and a current density of 26 mA / cm ² , which corresponds to an energy consumption of 6.4 W / kD.

An electroluminescent device is known where a zinc complex with ligands based on 8-aminoquinoline derivatives containing an electron-injecting layer, a hole transport layer, a hole-injecting layer and an active luminescent layer based on the above zinc chelate complex is used as an electroluminescent layer (RF patent No. 231067 C09K 11/06, 2006). The device emits in the blue-green region, has a brightness of 140 kD / m ² at a voltage of 19 V and a current density of 1.5 mA / cm ² (efficiency 9 kD / A).

RF patent No. 2265040 (IPC C09K 11/06, 2005) describes an electroluminescent material consisting of an electronic injection layer, an active luminescent layer based on a metal chelate complex, a hole transport layer and a hole injection layer. As a luminescent substance, it contains one of the hydroxyquinolate metal complexes of zinc 8-hydroxy-2-methoxyquininate or zinc 8-hydroxy-2-methylquinolinate. An electroluminescent material with radiation in the green region of the spectrum with increased thermal stability with the following parameters: brightness of 140 kD / m ^{2 is} achieved at a voltage of 16 V and a current density of 24 mA / cm ² (efficiency 4 kD / A).

The closest to implementation is an electroluminescent device, including a hole-injection layer (CuPc), a hole-transport layer (2-TNATA), an active luminescent layer based on an electroluminescent substance of bis [2- (2'-tosylaminophenyl) benzoxazolato] zinc (2+ ) of formula I

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hole-blocking layer (BCP), electron transport layer (Bphen), electron-injection layer (LiF). Such an ELU emits in the green region of the spectrum and has a brightness of 460 kD / m ² at a voltage of 8 V and a current of 30 mA / cm ² , which corresponds to a luminous efficiency of 0.67 Lm / W (RF patent No. 2408648, С09К 11/06, 2011 )

The objective of the invention is the expansion of electroluminescent devices with high performance, emitting in the green region of the spectrum.

The technical result is to increase the brightness of green radiation of electroluminescent devices with a luminescent layer based on chelate complexes of zinc with derivatives of salicylic aldehyde with various amines.

The technical result is achieved by an electroluminescent device, including a hole-injection layer (for example, CuPc), a hole-transport layer (for example, 2-TNATA), an active luminescent layer based on an electroluminescent substance of bis [2- (2′-tosylaminophenyl) benzoxazolato] zinc ( 2+) of general formula I, a hole-blocking layer (e.g., BCP), an electron transport layer (e.g., Bphen), an electron-injection layer (e.g., LiF), and an electronic blocking layer using N, N′- bis (3-methylphenyl) -N, N′bi (phenyl) -9,9-spirobifl Oren (spiro-TPD).

The difference between the device and the prototype is the presence of an electronic blocking layer and the use of N, N′-bis (3-methylphenyl) -N, N′bi (phenyl) -9,9-spirobifluorene (spiro-TPD) as it.

The invention meets the criterion of inventive step, since it is not known to increase the brightness of the radiation of an electroluminescent device when an additional electronic blocking layer is introduced into it, including based on spiro-TPD.

The synthesis of compound I is described in RF patent No. 2408648.

Figure 1 presents a General diagram of an electroluminescent device in longitudinal section. As a solid transparent substrate (1), a commercially available glass substrate is used with a transparent conductive layer of indium oxide doped with tin, which is an anode (2) and to which a metal contact (3) is connected. Then, a layer injecting holes of copper phthalocyanine (CuPc) (4), a hole transport layer (2-TNATA) (5), an electron-blocking layer of N, N′-bis (3-methylphenyl) -N are sequentially applied by thermal vacuum evaporation , N′bi (phenyl) -9,9-spirobifluorene (spiro-TPD) (6), light emitting layer of bis [2- (2′-tosylaminophenyl) benzoxazolato] zinc (II) (formula I) (7), hole blocking layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (8), electronic transport layer (4,7-diphenyl-1,10-phenanthroline) (BPhen) 9, electronic lithium fluoride (LiF) injection layer (10) and aluminum Todd (11). The dividing path (12) on the electrode coating of indium oxide doped with tin divides the transparent conductive layer into the anode (2) and cathode zones. The cathode zone was also a current path to the cathode (13) and has a metal contact (14). The thickness of the layers in the manufacture by thermal vacuum evaporation is strictly controlled.

Table 1 shows the chemical composition of the following substances, as well as the thickness of the functional layers of the device using the abbreviations of the compounds generally accepted in the literature:

Phthalocyanine Copper complex (CuPc), ALDRICH, CAS 147-148

4,4 ′, 4 ′ ′ - Tris (N- (2-naphthyl) -N-phenyl-amino) triphenylamine (2-TNATA)

KINTEC, lot: KZ88BuOMEEO, sales@kintec.hk

Spiro-TPD - N, N′-bis (3-methylphenyl) -N, N′bi (phenyl) -9,9-spirobifluorene SIGMA - ALDRICH, CAS 123847-85-8, CAS No. 189363-47-1

2,9-Dimethyl-4,7-diphenyl-1,10-phenanhroline (BCP) KINTEC, lot: KZ86BUOHRYO, sales@kintec.hk

4.7-Diphenyl-1,10-phenanthroline (Bphen) KINTEC, lot: KZ88BuOMEEO, sales@kintec.hk

LiF ALDRICH, CAS: 7789-24-4

                                                                                                                                    Table 1

No. p.p. Name amount one Glass plate one 2 Anode: ITO - In ₂ O ₃ : SnO ₂ one 3 Metal contact to the anode one four Hole injection layer: CuPc (copper phthalocyanine), layer thickness 3 nm one 5 Hole transport layer: 2-TNATA (4,4´, 4 ”-tri (2-naphthylphenyl-phenylamino) -triphenylamine),
layer thickness 40 nm one 6 Electronic blocking layer: spiro-TPD (N, N´-bi (phenyl) -9.9-spirobifluoren), layer thickness 6 nm one 7 Active luminescent layer: bis [2- (2'-tosylamino-phenyl) benzoxazolato] zinc (II), layer thickness 25 nm one 8 Hole blocking layer: BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), layer thickness 7 nm one 9 Electronic transport layer: BPhen (4,7-diphenyl-1,10-phenanthroline), layer thickness 28 nm one 10 Electronic injection layer: LiF, layer thickness 1.0 nm one eleven Cathode: Al (100 nm) one 12 Dividing path one 13 Current lead to the cathode one fourteen Metal contact to the cathode one

Before use, the substance is subjected to repeated purification by reprecipitation. The formation of multilayer structures of acid and the measurement of performance is carried out in an inert atmosphere Ar in the absence of contact with the atmosphere. The layers are applied by thermal vacuum evaporation.

When voltage is applied to the anode (2) and cathode (11), holes and electrons are injected into neighboring conductive layers, respectively, which move towards each other. In the light-emitting layer (7), these charges recombine, which causes the effect of electroluminescence (light emission). The blocking layers (6) and (8) provide the accumulation of electrons and holes in the layer (7), thereby increasing the efficiency of charge recombination, i.e. radiation intensity.

In FIG. Figure 1 shows the structure of the manufactured acid based on a zinc complex with green light radiation.

The obtained spectra of photo and electroluminescence (EL) are shown in figures 2 and 3.

It was established that in the wavelength range from 500 to 750 nm at a thickness of said layers of OLED emission brightness obtained is 2500 cd / m ² under an applied potential of 10 V. The threshold voltage is 3.2 V. emission chromaticity coordinates - (x = 0.373; y = 0.463 )

Thus, electroluminescent devices based on a luminescent compound with the formula I using an electronic blocking layer based on N, N′-bis (3methylphenyl) -N, N′bi (phenyl) -9,9-spirobifluorene (spiro-TPD) show high performance characteristics exceeding the brightness characteristic of the prototype by 5 times, which allows it to be used as a radiating organic material in green light sources.

This confirms the achievement of the technical result in comparison with the well-known technical solution, as well as the expansion of the range of acid.

Claims (1)

An electroluminescent device including a hole-injection layer, a hole-transport layer, an active luminescent layer based on an electroluminescent compound of bis [2- (2'-tosylaminophenyl) benzoxazolato] zinc (2+) of formula I,

I
hole-blocking layer, electron-transport layer, electron-injecting layer and electron blocking layer using N, N´-bis (3-methylphenyl) -N, N´bi (phenyl) -9,9-spirobifluorene as it.

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