WO2018184869A1 - Wavelength converter and optoelectronic component - Google Patents

Abstract

The invention relates to a wavelength converter (300) comprising at least one quantum dot (400) which is enveloped in an optical shell (500).

Description

 WAVELENGTH CONVERTER AND OPTOELECTRONIC COMPONENT

DESCRIPTION The present invention relates to a wavelength converter and an optoelectronic component.

This patent application claims the priority of German Patent Application DE 10 2017 107 429.5, the disclosure of which is hereby incorporated by reference.

Wavelength converter optoelectronic devices which convert light emitted from one optoelectronic semiconductor chip to light of another wavelength are known in the art. Is also known to use quantum dots in such ^¬ wavelength converters for wavelength conversion.

An object of the present invention is to provide a wavelength converter. Another object of the present invention is to provide an optoelectronic device. These objects are achieved by a wavelength converter and by an optoelectronic component having the features of the independent claims. In the dependent claims various developments are given.

A wavelength converter comprises at least one quantum dot enveloped in an optical dish. The optical shell of the quantum dot of this wavelength converter can form an optical resonator, by means of which, by utilizing the Purcell effect, coupling modes of a pump light exciting the quantum dot and / or a converted light which can be emitted by the quantum dot to the quantum dot is improved becomes. This makes it possible to increase a probability of absorption and / or emission ^¬ probability of the quantum dot optical cup. This can the wavelength converter advantageously have a high conversion efficiency.

In general, the wavelength converter will have a plurality of similar quantum dots, which are each encased in an optical shell. Advantageously, the wavelength converter can achieve a higher conversion efficiency than conventional wavelength converters due to the high conversion efficiency of its quantum dots with the same number of quantum dots per volume of the wavelength converter. Alternatively, with a reduced number of quantum dots per volume of the wavelength converter, a comparable conversion efficiency can be achieved as with conventional wavelength converters. A reduced number of quantum dots per volume of the wavelength converter can result in cost savings. If the quantum dots contain cadmium, a reduced number of quantum dots per volume of the wavelength converter can also result in a reduced environmental impact.

In one embodiment of the wavelength converter, the quantum dot has a quantum dot core and a quantum dot shell enclosing the quantum dot core. The optical shell envelops the quantum dot shell. Vorteilhafter- as suitable quantum dots having a quantum dot ^¬ core and a shell quantum dot-containing structure particularly suitable for use for wavelength conversion.

In one embodiment of the wavelength converter, the quantum dot core has CdSe while the quantum dot shell has CdS. Advantageously, quantum dots comprising this combination of materials are suitable for wavelength conversion in the visible spectral range or in adjacent ones

Spectral regions. As a result, such quantum dots are particularly well suited for use in wavelength converters.

In one embodiment of the wavelength converter, the quantum dot is formed, light having a wavelength of 450 nm to absorb and emit light with a wavelength of 620 nm. Advantageously, the quantum dot and thus the wavelength converter in this case are suitable for converting blue light into light having a wavelength from the orange-red spectral range. As a result, the wavelength converter is suitable, for example, for producing white mixed light.

In one embodiment of the wavelength converter of the quantum dot has a radius between 10 nm and 20 nm, wherein ^¬ play a radius of 15 nm. Advantageously, the quantum dots are having a radius in this size range particularly suitable for use in wavelength converters. In one embodiment of the wavelength converter, the optical shell comprises a transparent material. It is particularly advantageous if the material of the optical cup in the wavelength range of the pump light with which the quantum dot can be excited, and / or in the wavelength range of abstrahlbaren of the quantum dot emission ^¬ light, has high transparency. Advantageously, losses caused by the optical shell of the quantum dot of the wavelength converter are thereby small. In one embodiment of the wavelength converter, the material of the optical shell comprises Al ₂ O ₃ . Advantageously, Al ₂ O ₃ has a high transparency in many applications for a wavelength converter ^¬ relevant wavelength regions. For example, an Al ₂ O ₃ -containing optical dish is suitable for use in a wavelength converter designed to convert light having a wavelength from the blue spectral region to light having a wavelength from the yellow, orange or red spectral region.

In one embodiment of the wavelength converter, the optical shell has a thickness between 100 nm and 800 nm, in particular a thickness between 300 nm and 500 nm, in particular particular a thickness of between 400 nm and 450 nm, particularly a thickness between 410 nm and 425 nm. Advantageously, Model calculations and experimental results indicate that the quantum ^¬ dots, which are wrapped in an optical cup of such a thickness that can have a particularly high conversion efficiency.

In one embodiment of the wavelength converter, this has a matrix material. The quantum dot is embedded in the matrix material. Advantageously, the wavelength converter can thereby be processed in a simple manner and arranged in an optoelectronic component.

In one embodiment of the wavelength converter, the matrix material comprises a silicone. This is advantageous

Matrix material of the wavelength converter in this case kos ^¬ tengünstig available, easy to work with and has a high resistance. An optoelectronic component comprises an optoelectronic ^¬ African semiconductor chip and a wavelength converter of the aforementioned type.

Advantageously, the wavelength converter of this optoelectronic component can serve to at least partially convert light emitted by the optoelectronic semiconductor chip into light of another wavelength. By way of example, the wavelength converter can serve light emitted by the optoelectronic semiconductor chip with a wavelength from the blue or ultraviolet

Spectral range in light with a wavelength from the gel ^¬ ben, orange or red spectral range to convert. The wavelength converter may advantageously have a particularly high conversion efficiency. The optoelectronic semiconductor chip can be, for example, a light-emitting diode chip (LED chip). The above-described characteristics, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments which will be described in connection with the drawings. In each case show in a schematic representation

FIG. 1 shows a sectional side view of an optoelectronic component with an optoelectronic component

Semiconductor chip and a wavelength converter;

Figure 2 is a sectional side view of the wavelength converter ^¬;

FIG. 3 shows a first shell thickness dependency diagram; and

FIG. 4 shows a second shell thickness dependency diagram. FIG. 1 shows a sectional side view of an opto ^¬ electronic component 100 in a schematic representation. The optoelectronic component 100 is intended to emit electromagnetic radiation, for example visible

Light, to radiate. The optoelectronic component 100 may for example be provided to testify white light ^¬ to it. The optoelectronic component 100 may ^¬ example, a light emitting device (LED) device be.

The optoelectronic component 100 has an optoelectronic semiconductor chip 200. The optoelectronic semi ^¬ conductor chip 200 can be for example a light emitting diode chip (LED chip). The optoelectronic semiconductor chip 200 is adapted to emit electromagnetic radiation with a wave length ^¬ from a pump wavelength range. Examples game, the optoelectronic semiconductor chip 200 may be configured to emit electromagnetic radiation with a Wel ^¬ lenlänge from the blue or ultraviolet spectral range. The of the optoelectronic semiconductor chip 200 emitted electromagnetic radiation can, for example ^{¬ have} a wavelength between 320 nm and 500 nm. Electromagnetic radiation emitted by the optoelectronic semiconductor chip 200 is referred to below as pumping light 110.

In the example shown in FIG. 1, the optoelectronic semiconductor chip 200 is designed as a surface-emitting light-emitting diode chip. By the optoelectronic semiconductor chip 200 emitted pumping light 110 of the optoelectronic semiconductor chip 200 from ^¬ is irradiated at a Strahlungsemissi ^¬ onsfläche 210th The optoelectronic semiconductor chip 200 could, however, also be embodied, for example, as a volume-emitting LED chip. In this case, pump light 110 emitted by the opto-electronic semiconductor chip 200 would also be emitted at side surfaces of the optoelectronic semiconductor chip 200.

The optoelectronic device 100 further includes a wavelength converter 300. The wavelength converter 300 is provided, at least to convert a part of light emitted from the optoelekt ^¬ tronic semiconductor chip 200 of the optoelectronic component 100 pumping light 110 in converted light 120 having a wavelength of a Konversionswellenlängen- area. In this case 120, the converted light has a longer wavelength than the pumping light 110. In ^¬ play which may converted by the wavelength converter 300 light 120 having a wavelength in the red, oran ^¬ gen, yellow or green spectral range. For example, the converted light 120 may have a wavelength between 500 nm and 800 nm.

If the wavelength conversion by the wavelength converter 300, by at least a part of the light emitted by the opto-electronic ^¬ semiconductor chip 200 pump light is absorbed in the wavelength converter 300 110th The absorbed energy is the wavelength converter 300 at least in part by radiation of the converted light 120 again.

Figure 2 shows a highly schematic representation of the WEL lenlängenkonverters 300 of the optoelectronic device 100. The wavelength converter 300 includes a matrix material 310 and at least one eingebet ^¬ ended in the matrix material 310 to the quantum dot 400. In practice, the Wellenlän ^¬ genkonverter 300 will have a very large number of similarly-trained and the matrix material 310 embedded quantum dots 400th However, only one of these quantum dots 400 is shown in the schematic representation of FIG. The matrix material 310 of the wavelength converter 300 may comprise, for example, a silicone. However, the matrix material 310 of the wavelength converter 300 may also include an epoxide, egg ^¬ ne mixture of an epoxide and a silicone or another material.

The quantum dot 400 is designed to light emitted from the optoelekt ^¬ tronic semiconductor chip 200 pump light 110 to absorb at a wavelength from the pump wavelength range. After absorption of a photon of the pumping light 110 of the quantum dot 400 may emit a quantum of converting light 120 having a wavelength from the Konversionswellenlängenbe ^¬ rich. For example, the quantum dot 400 may be configured to absorb pump light 110 having a wavelength of 450 nm emitted by the optoelectronic semiconductor chip 200. Further, the quantum dot 400 may be configured to emit converted light 120 having a wavelength of 620 nm, for example.

In the example shown, the quantum dot 400 has a quantum dot core 410 and a quantum dot shell 420 enveloping the quantum dot core 410. The quantum dot core 410 may include, for example, CdSe. The quantum dot shell 420 may include, for example, CdS. The quantum dot 400 but could also have other materials. It is also possible that the quantum dot 400 is not formed with the quantum dot core ^¬ 410 and quantum dot shell 420, but for example, as material unitary body.

The quantum dot 400 is formed in the illustrated example in wesent ^¬ union spherical and has a radius 401 on. The radius 401 of the quantum dot 400 may be, for example, between 10 nm and 20 nm. For example, the radius 401 of the quantum dot 400 may be 15 nm.

If the wavelength converter 300 comprises a plurality of quantum dots 400, so preferably, all of the quantum dots 400 Wel ^¬ lenlängenkonverters 300 has a similar shape and size. The indicated values of the radius 401 may, for example, form a median value (D50 value) of the radii 401 of the quantum dots 400.

The quantum dot 400 is enveloped in an optical shell 500. The optical cup 500 has, in the illustrated case ^¬ match the shape of a spherical shell having a thickness of 501.

The optical shell 500 has a dielectric material which has the highest possible transparency in the pump wavelength range and in the conversion wavelength range. In ^¬ play, the optical cup 500 may include Al ₂ O _3. Al ternatively, the optical ^¬ shell 500 could have, for example, Ti0 ₂ or Si0. ₂ The quantum dot 400 enveloping optical cup 500 bil ^¬ det a resonator of a coupling of modes

Pumplichts 110 and / or converted by modes of the converted light 120 to the quantum dot 400. This is known as the Purcell effect. By increasing the coupling of modes of the pump light 110 to the quantum dot 400, the International ^¬ probability of absorption of a photon of the pumping light is increased by the quantum dot 400 110th By increasing the coupling of modes of the converted light 120 to the Quantum dot 400, the probability of emission of a quantum of the converted light 120 is increased by the quantum dot 400. As a result, the optical shell 500 can cause an increase in conversion efficiency of the wavelength converter 300.

The refractive indices of the materials of the quantum dot 400, the optical shell 500 and the matrix material 310, and the radius 401 of the quantum dot 400 and the thickness 501 of the optical shell 500 are matched to one another such that the optical shell 500 is the coupling of modes of the

Pumplichts 110 to the quantum dot 400 and / or Ankopp ^¬ ment of modes of the converted light 120 to the quantum dot 400 increases. Preferably, the mentioned parameters are selected such that both the coupling of modes of the pumping light 110 to the quantum dot 400 and the coupling of modes of the converted light 120 to the quantum dot 400 are increased ^relative to a situation without an optical shell 500. However, it is also possible that either only the coupling of modes of the pumping light 110 to the quantum dot 400 or only the coupling of modes of the converted light 120 to the quantum dot 400 is increased in relation to a situation without an optical shell 500. Suitable values of these parame ^¬ ter can be experimentally or by modeling ER auxiliaries.

FIG. 3 shows a schematic representation of a first shell thickness dependency diagram 600. FIG. 4 shows a schematic representation of a second shell thickness dependency graph 601. The first shell thickness dependency graph 600 and the second shell thickness dependency graph 601 provide a dependence of the coupling of modes of the pump light 110 and of the Coupling of modes of the converted light 120 to the quantum dot 400 as a function of each aufgetra ^¬ on the horizontal axis thickness 501 of the optical shell 500 at. The model calculations shown in Figures 3 and 4 were carried out for the case that the quantum dot of the quantum dot core 410 having 400 CdSe, while the quantum dot ^¬ cup 420 of the quantum dot comprises 400 CdS. The radius 401 of the quantum dot 400 in the model is 15 nm. The pumping light 110 has a wavelength of 450 nm in the model. The converted light 120 has a wavelength of 620 nm in the case of the model calculation. The optical shell 500 of the quantum dot 400 has Al ₂ O ₃ in the model calculation.

In the first shell thickness dependency diagram 600 shown in FIG. 3, an absorption profile 610 gives the dependence of the probability of absorption of a quantum of the pumping light 110 by the quantum dot 400 as a function of

Thickness 501 of the optical shell 500 on. In the second shell thickness dependency diagram 601 shown in FIG. 4, an emission profile 620 indicates the probability of emission of a quantum of the converted light 120 by the quantum dot 400 as a function of the thickness 501 of the optical shell 500. It can be seen that in a favorable thickness range 502 of the thickness 501 both the probability of absorption of a quantum of the pumping light 110 by the quantum dot 400 and the probability of emission of a quantum of the converted light 120 by the quantum dot 400 have high values. The favorable thickness range 502 is located in the illustrated example, approximately between 410 nm and 425 nm, in particular ^¬ sondere at about 420 nm. In general, the thickness 501 of optical cup 500 for example between 100 nm and 800 nm, insbesonde ^¬ re between 300 nm and 500 nm, in particular between 400 nm and 450 nm. the invention has been based on the preferred Ausführungsbei ^¬ games further illustrated and described. However, the invention is not limited to the disclosed examples. Rather, other variations can be deducted from this by the expert. be directed, without departing from the scope of the invention.

LIST OF REFERENCE NUMBERS

100 optoelectronic component 110 pump light

 120 converted light

200 optoelectronic semiconductor chip

 210 radiation emission surface

300 wavelength converters

310 matrix material 400 quantum dot

 401 radius

410 quantum dot core

 420 quantum dot shell

500 optical shell

 501 thickness

 502 favorable thickness range 600 first shell thickness dependency diagram 601 second shell thickness dependency plot

610 absorption course

620 Emission history

Claims

PATENTA'S TEST 1. Wavelength converter (300) with at least one quantum dot (400), which is wrapped in a op ^¬ diagram shell (500). 2. wavelength converter (300) according to claim 1,  wherein the quantum dot (400) has a quantum dot core (410) and a quantum dot shell (420) enveloping the quantum dot core (410),  wherein the optical shell (500) envelops the quantum dot shell (420). 3. wavelength converter (300) according to claim 2,  wherein the quantum dot core (410) comprises CdSe and the quantum dot shell (420) comprises CdS. 4. wavelength converter (300) according to one of the preceding claims,  wherein the quantum dot (400) is configured to absorb light (110) having a wavelength of 450 nm and to emit light (120) having a wavelength of 620 nm. 5. wavelength converter (300) according to one of the preceding claims,  wherein the quantum dot (400) has a radius (401) between 10 nm and 20 nm, in particular a radius (401) of 15 nm. 6. wavelength converter (300) according to one of the preceding claims, wherein the optical shell (500) has a transparent Materi ^¬ al. 7. wavelength converter (300) according to one of the preceding claims, wherein the material of the optical shell (500) AI ₂ O ₃ has ^¬ . 8. wavelength converter (300) according to one of the preceding claims,  wherein the optical shell (500) has a thickness (501) between 100 nm and 800 nm, in particular a thickness (501) between 300 nm and 500 nm, in particular a thickness (501) between 400 nm and 450 nm, in particular a thickness (501). 501) between 410 nm and 425 nm. 9. wavelength converter (300) according to one of the preceding claims,  wherein the wavelength converter (300) comprises a matrix material (310),  wherein the quantum dot (400) is embedded in the matrix material (310). 10. wavelength converter (300) according to claim 9,  wherein the matrix material (310) comprises a silicone. 11. Optoelectronic component (100)  with an optoelectronic semiconductor chip (200)  and a wavelength converter (300) according to one of the preceding claims.