STRUCTURE, OPTOELECTRONIC DEVICE AND METHOD FOR PRODUCING A STRUCTURE

Abstract

A structure, an optoelectronic device and a method for producing a structure are disclosed. In an embodiment, a structure comprises a first nanoparticle comprising at least one semiconductor material. The first nanoparticle is chromophoric in a first wavelength range and emissive in a second wavelength range. The structure further comprises a plurality of second nanoparticles. The second nanoparticles are non-chromophoric in the first wavelength range and in the second wavelength range.

Claims

1. A structure comprising: a first nanoparticle comprising at least one semiconductor material, wherein the first nanoparticle is chromophoric in a first wavelength range and emissive in a second wavelength range; and a plurality of second nanoparticles, wherein the second nanoparticles are non-chromophoric in the first wavelength range and in the second wavelength range.

2. The structure according to claim 1, wherein the first nanoparticle comprises a core and at least one shell.

3. The structure according to claim 1, wherein the second nanoparticles comprise particles selected from the group consisting of metallo-particles, semiconductor particles, chalcogenide particles pnictide particles, and combinations thereof.

4. The structure according to claim 1, further comprising an encapsulation.

5. The structure according to claim 4, wherein the first nanoparticle and the second nanoparticles are spaced apart within the encapsulation.

6. The structure according to claim 1, wherein each second nanoparticle of the plurality of second nanoparticles is in direct contact with at least one of the first nanoparticle and a further second nanoparticle of the plurality of second nanoparticles.

7. The structure according to claim 1, wherein the second nanoparticles are bonded to the first nanoparticle by at least one method selected from the group consisting of aggregating, non-covalent binding, covalent binding, melting, sintering, agglomerating, and combinations thereof.

8. The structure according to claim 1, wherein a surface of the first nanoparticle is partially covered by the second nanoparticles.

9. The structure according to claim 1, wherein a surface of the first nanoparticle is completely covered by the second nanoparticles.

10. The structure according to claim 1, wherein the second nanoparticles comprise at least one surface moiety.

11. The structure according to claim 10, wherein the second nanoparticles comprise a first surface moiety and a second surface moiety, wherein the first surface moiety is bonded to the second nanoparticles by the second surface moiety.

12. The structure according to claim 1, wherein the structure comprises at least one internal payload species in close proximity to the first nanoparticle.

13. The structure according to claim 12, wherein the at least one internal payload species is internal to the second nanoparticles.

14. The structure according to claim 1, wherein the first nanoparticle is encapsulated in a first encapsulation, wherein the second nanoparticles are encapsulated in a second encapsulation, and wherein the first encapsulation and the second encapsulation are in direct contact with each other.

15. The structure according to claim 14, wherein the first encapsulation and the second encapsulation comprise the same encapsulation material.

16. An optoelectronic device comprising: a semiconductor chip configured to emit a primary radiation; and a conversion element configured to convert at least a portion of the primary radiation into a secondary radiation; wherein the conversion element comprises at least one structure according to claim 1.

17. A method for producing a structure, comprising: providing a first nanoparticle comprising at least one semiconductor material, wherein the first nanoparticle is chromophoric in a first wavelength range and emissive in a second wavelength range; providing a plurality of second nanoparticles, wherein the second nanoparticles are non-chromophoric in the first wavelength range and in the second wavelength range; and arranging the first nanoparticle and the second nanoparticles in close proximity to each other.

18. The method according to claim 17, further comprising bonding the second nanoparticles to the first nanoparticle by at least one method selected from the group comprising aggregating, non-covalent binding, covalent binding, melting, sintering, agglomerating, and combinations thereof.

19. The method according to claim 17, further comprising applying an encapsulation.

20. The method according to claim 17, further comprising encapsulating the first nanoparticle in a first encapsulation; encapsulating the second nanoparticles in a second encapsulation; and arranging the first encapsulation and the second encapsulation in direct contact with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Advantageous embodiments and developments of the structure, the optoelectronic device, and the method for producing a structure will become apparent from the exemplary embodiments described below in conjunction with the figures.

[0076] In the figures:

[0077] FIGS. 1, 4A, 4B, 6, 8, 10, and 12 each show a schematic illustration of a structure according to different exemplary embodiments,

[0078] FIGS. 2, 5A-C, 7A, 7B, 9, 11, and 13 each show a schematic illustration of a method for producing a structure according to different exemplary embodiments,

[0079] FIG. 3 shows a transmission electron microscopy (TEM) micrograph of a structure according to an exemplary embodiment, and

[0080] FIG. 14 shows a schematic illustration of an optoelectronic device according to an exemplary embodiment.

[0081] In the exemplary embodiments and figures, similar or similarly acting constituent parts are provided with the same reference symbols. The elements illustrated in the figures and their size relationships among one another should not be regarded as being true to scale. Rather, individual elements may be represented with an exaggerated size for the sake of better representability and/or for the sake of better understanding.

DETAILED DESCRIPTION

[0082] FIG. 1 shows a schematic illustration of a structure 1. The structure 1 comprises a first nanoparticle 2. The first nanoparticle 2 comprises at least one semiconductor material. For example, the first nanoparticle is a photoluminescent quantum dot such as a CdSe/CdS/ZnS core-shell-shell quantum dot. The first nanoparticle 2 is chromophoric in a first wavelength range and emissive in a second wavelength range. In other words, the first nanoparticle 2 may absorb electromagnetic radiation of the first wavelength range and emit electromagnetic radiation in the second wavelength range. For example, the first wavelength range comprises wavelengths between and including 400 nm and 490 nm and the second wavelength range comprises wavelengths between and including 500 nm and 2000 nm, in particular between and including 500 nm and 700 nm.

[0083] The structure further comprises a plurality of second nanoparticles 3. The second nanoparticles 3 are non-chromophoric in the first wavelength range and in the second wavelength range. In other words, the second nanoparticles 3 neither absorb wavelengths in the first wavelength range nor in the second wavelength range. Alternatively, the second nanoparticles 3 absorb significantly less electromagnetic radiation in both the first and the second wavelength range than a particle that is chromophoric in said wavelength ranges. For example, the second nanoparticles 3 are metallo-particles, semiconductor particles, such as II-VI semiconductors, chalcogenide particles, such as nano-ZnS or nano-ZnO, pnictide particles, and combinations thereof. The second nanoparticles 3 are co-located with the first nanoparticle 2 within the structure 1 meaning that the second nanoparticles 3 are arranged in close proximity to the first nanoparticle 2. In particular, a distance between the first nanoparticle 2 and the second nanoparticles 3 is between and including 0 μm and 30 μm. The second nanoparticles 3 have an equal or greater affinity for degrading species likely to degrade the first nanoparticle 2 by intercepting and chemically reacting with and/or absorbing the degrading species.

[0084] Optionally, the structure 1 may comprise an encapsulation 4 at least partially, or completely, surrounding the first nanoparticle 2 and the second nanoparticles 3. In this instance, the first nanoparticle 2 and the second nanoparticles 3 may be co-encapsulated in the encapsulation 4. The encapsulation 4 may comprise or consist of an encapsulation material comprising or consisting of metal oxides such as silica.

[0085] The structure 1 according to FIG. 1 may be produced according to FIG. 2 by admixing the first nanoparticle 2 and the second nanoparticles 3 prior to forming an encapsulation 4 around the nanoparticles. This is sufficient to provide a statistically distributed random co-encapsulation of second nanoparticles 3 and the first nanoparticle 2.

[0086] In a further embodiment of the structure 1 according to FIG. 1, the first nanoparticle 2 is a CdSe/CdS/ZnS photoluminescent quantum dot and the second nanoparticles 3 are nano-ZnS particles. Optionally, the first nanoparticle 2 and the second nanoparticles 3 are co-encapsulated in an encapsulation 4 of silica. In this case, the nano-ZnS stabilizes the degradation of the ZnS layer of the multi-shell quantum dot through one or more of several mechanisms. The nano-ZnS may provide a constant level of dissolved ZnS (Zn.sup.2+ and S.sup.2−) near the quantum dot slowing dissolution. The nano-ZnS may also provide a repository for damaging redox equivalents photo-generated during the material aging, for example, photo-oxidation via Auger processes. The nano-ZnS may trap superoxide, hydroxy radicals, and other reactive oxygen species. The nano-ZnS may further provide a source of ZnS monomer to redeposit upon the partial corroded quantum dot.

[0087] FIG. 3 shows a TEM micrograph of a structure 1 comprising a CdSe/CdS/ZnS first nanoparticle 2 co-encapsulated in a silica encapsulation 4 with nano-ZnS second nanoparticles 3. The mere proximity of the nano-ZnS second nanoparticles 3 is sufficient to create a preservative effect in the composite system of the CdSe/CdS/ZnS first nanoparticle 2.

[0088] The structures 1 according to FIGS. 4A and 4B differ from the structure according to FIG. 1 in that each second nanoparticle 3 is in direct contact to at least one of the first nanoparticle 2 and a further second nanoparticles 3.

[0089] The first nanoparticle 2 and the second nanoparticles 3 form an assembly. Optionally, the assembly may be encapsulated with an encapsulation 4. The surface of the first nanoparticle 2 may be partially (FIG. 4A) or completely (FIG. 4B) covered with the second nanoparticles 3. In other words, the second nanoparticles 3 form a layer around the first nanoparticle 2. The layer of second nanoparticles 3 may have a thickness of between and including 1 nm and 100 nm, for example, between and including 1 nm and 20 nm or between and including 1 nm and 10 nm.

[0090] The structures 1 according to FIGS. 4A and 4B may be produced according to FIGS. 5A and 5B by forming an assembly of the first nanoparticle 2 and the second nanoparticles 3 and optionally encapsulating the assembly with an encapsulation 4.

[0091] The assembly may be prepared in such a way that the second nanoparticles 3 are bonded to the first nanoparticle 2 by at least one of aggregating, noncovalent binding, covalent binding, and agglomerating. For example, the first nanoparticle 2 and the second nanoparticles 3 may be prepared in such a way that, accounting for bound and charged ligands, the nanoparticles 2, 3 are oppositely charged. The oppositely charged nanoparticles 2, 3 may be allowed to aggregate into structures 1. Alternatively, for attaining an even higher level of control, the first nanoparticle 2 and the second nanoparticles 3 may be covalently linked, for example, via organic ligands bound to a surface of the first nanoparticle 2 and the second nanoparticles 3 that chemically react with one another.

[0092] As shown in FIG. 5C, two different types of second nanoparticles 3, 3′ may be provided for forming the assembly with the first nanoparticle 2. The two different types of second nanoparticles 3, 3′ differ from one another in at least one of: size, composition, and shape. For example, the second nanoparticles 3 have a different composition then the second nanoparticles 3′. The structure 1 then comprises a mixed layer of the two types of second nanoparticles 3, 3′ on the surface of the first nanoparticle 2.

[0093] FIG. 6 shows a structure 1 that differs from the structure 1 according to FIGS. 4A and 4B in that the second nanoparticles 3 are partially melted or lightly sintered to the first nanoparticle 2. The partially melted or lightly sintered second nanoparticles 3 form a melted or sintered structure 5 surrounding the first nanoparticle 2 at least partially, or completely. The melted or sintered structure 5 may have the form of a layer surrounding the first nanoparticle 2 having a thickness of between and including 1 nm and 100 nm, for example, between and including 1 nm and 20 nm or between and including 1 nm and 10 nm.

[0094] The structure according to FIG. 6 may be produced according to FIG. 7A by providing second nanoparticles 3 in proximity to a first nanoparticle 2. By applying a temperature, for example, of between and including 90° C. and 400° C., the second nanoparticles 3 are melted and/or sintered to the surface of the first nanoparticle 2 forming a melted or sintered structure 5. By further applying the temperature, multiple sintering events expand the coverage of the first nanoparticle 2 with the melted or sintered structure 5. In a further embodiment, the surface of the first nanoparticle 2 is completely covered by the melted or sintered structure 5.

[0095] Optionally, the first nanoparticle 2 and the second nanoparticles 3 may be co-encapsulated in an encapsulation 4 following various degrees of melting or sintering.

[0096] Instead of using one type of second nanoparticles 3, two different types of second nanoparticles 3, 3′ may be provided and melted and/or sintered to the first nanoparticle 2 as shown in FIG. 7B forming a melted or sintered structure 5′ on the surface of the first nanoparticle 2. The melted or sintered structure 5′ is a mixed layer of both types of second nanoparticles 3, 3′.

[0097] FIG. 8 shows a structure 1 comprising a first nanoparticle 2 encapsulated in a first encapsulation 6 and second nanoparticles 3 encapsulated in a second encapsulation 7. The first encapsulation 6 and the second encapsulation 7 are in direct contact and thus the first nanoparticle 2 and the second nanoparticles 3 are in close proximity. The first encapsulation 6 and the second encapsulation 7 may comprise the same encapsulation material, for example, silica.

[0098] The structure 1 according to FIG. 8 may be produced according to FIG. 9 by encapsulating the first nanoparticle 2 in a first encapsulation 6, in particular homogeneously, and by encapsulating the second nanoparticles 3 in a second encapsulation 7, in particular homogeneously. Each second nanoparticle 3 may be individually encapsulated or a plurality of second nanoparticles 3 may be encapsulated together. The pre-encapsulated nanoparticles 2, 3 are then admixed and agglomerated or aggregated or fused to form the structure 1.

[0099] FIG. 10 shows a structure 1 with an intermediate structure 10 of second nanoparticles 3 comprising surface moieties 8, 9, wherein the first surface moiety 8 is bonded to the second nanoparticles 3 by a second surface moiety 9. The second surface moiety 9 may be a polymer or a molecular species with an affinity for binding the first surface moiety. The first surface moiety 8 may be an organic or an inorganic molecule or species. The first surface moiety 8 is, for example, poly-ethyleneglycol which, through its affinity for water, may enhance the moisture of the environment near the first nanoparticle 2. Alternatively, the first surface moiety 8 may be a reductant or an oxidant such as borans, borohydrides, citrates, oxalates, reducing sugars, aldehydes, or hydrazine iodide, sulfites, thiosulfates, and dithionates.

[0100] In the exemplary embodiment of FIG. 10, the second nanoparticles 3 themselves may be inactive meaning the second nanoparticles 3 have no interaction with the species likely to degrade the first nanoparticle 2. In this case, the second nanoparticles 3 are utilized more for their surface moiety carrying capacity. Alternatively, the second nanoparticles 3 may be active meaning the second nanoparticles 3 have an interaction with the species likely to degrade the first nanoparticle 2. In both cases, the nanoscale size of the second nanoparticles 3 provides a means to entrap the second nanoparticles 3 together with the surface moieties 8, 9 in the same vicinity as the first nanoparticle 2. This contrasts with ions or small molecules which may, more or less freely, diffuse through a surrounding media such as a silica encapsulation.

[0101] The structure 1 according to FIG. 10 may be produced according to FIG. 11 by preparing the intermediate structure 10 comprising second nanoparticles 3 decorated with the surface moieties 8, 9 by binding the second surface moiety 9 to the surface of the second nanoparticles 3 and by binding the first surface moiety 8 to the second surface moiety 9. Subsequently, the second nanoparticles 3 decorated with the surface moieties 8, 9 are arranged in close proximity to the first nanoparticle 2 and optionally encapsulated together with the first nanoparticle 2 in an encapsulation 4.

[0102] FIG. 12 shows a structure 1 in which at least one of the second nanoparticles 3 comprises an internal payload species A and at least one of the second nanoparticles 3 comprises a second internal payload species B. The first internal payload species A and the second internal payload species B differ from one another in at least one of: composition and charge number. The respective internal payload species A, B is internal to the second nanoparticles 3 rather than surface attached. In particular, the internal payload species A, B is substitutionally or interstitially incorporated into the lattices of the second nanoparticles 3. The internal payload species A, B includes, for example, copper(I), iron(II), mercury, and combinations thereof.

[0103] In the structure 1 of FIG. 12, the second nanoparticles 3 may act as a buffer that provides a stream of ions of the internal payload species A, B in the vicinity of the first nanoparticle 2. It should be noted that the internal payload species A, B provides its effect when released in proximity to the first nanoparticle and not when bonded on and/or in the second nanoparticles 3. In particular, the second nanoparticles 3 function as a carrier for bringing the internal payload species A, B in the vicinity of the first nanoparticle 2 functioning as a slow release drug.

[0104] The structure 1 according to FIG. 12 may be produced according to FIG. 13 by admixing the first nanoparticle 2 and the second nanoparticles 3 comprising the internal payload species A, B prior to forming an encapsulation 4 around the nanoparticles 2, 3. During and after encapsulation, the second nanoparticles 3 provide the internal payload species A, B in proximity to the first nanoparticle 2.

[0105] FIG. 14 shows a schematic illustration of an optoelectronic device 100 comprising a semiconductor chip 101 with an active layer stack and an active region (not explicitly shown here). During operation, the semiconductor chip 101 emits a primary radiation, for example, from the radiation emission surface 102. In particular, the primary radiation is an electromagnetic radiation of the first wavelength range. For example, the semiconductor chip 101 emits electromagnetic radiation in the visible wavelength range, in particular in the blue wavelength range, for instance in a wavelength range between and including 400 nm and 490 nm such as 450 nm.

[0106] A conversion element 103 is arranged on the radiation emission surface 102 of the semiconductor chip 101. In particular, the conversion element is arranged in direct contact to the radiation emission surface 102. The conversion element 103 is configured or designed to absorb the primary radiation and convert at least a portion of the primary radiation into secondary radiation. The secondary radiation is an electromagnetic radiation with a wavelength range at least partially, or completely, different from the primary radiation. In particular, the secondary radiation is an electromagnetic radiation of the second wavelength range, for example, having wavelengths between and including 500 nm and 2000 nm, such as between and including 500 nm and 700 nm.

[0107] The conversion element 103 comprises or consists of at least one structure 1. For example, the conversion element 103 comprises at least one structure 1, in particular a plurality of structures 1, as shown in conjunction with FIGS. 1, 3, 4A, 4B, 6, 8, 10, and 12. In particular, the at least one structure 1 may be embedded in a matrix material such as silicone, polysiloxane or epoxy.

[0108] The features and exemplary embodiments described in connection with the figures may be combined with each other according to further exemplary embodiments, even if not all combinations are explicitly described. Furthermore, the exemplary embodiments described in connection with the figures may have alternative or additional features as described in the general part.

[0109] The invention is not restricted to the exemplary embodiments by the description on the basis of said exemplary embodiments. Rather, the invention encompasses any new feature and also any combination of features, which in particular comprises any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

REFERENCES

[0110] 1 structure [0111] 2 first nanoparticle [0112] 3, 3′ second nanoparticle [0113] 4 encapsulation [0114] 5, 5′ melted or sintered structure [0115] 6 first encapsulation [0116] 7 second encapsulation [0117] 8 first surface moiety [0118] 9 second surface moiety [0119] 10 intermediate structure [0120] A first internal payload species [0121] B second internal payload species [0122] 100 optoelectronic device [0123] 101 semiconductor chip [0124] 102 radiation emission surface [0125] 103 conversion element