Method for Producing a Structured Wavelength Conversion Layer and Optoelectronic Device with a Structured Wavelength Conversion Layer

Abstract

In an embodiment a method for producing a structured wavelength conversion layer includes providing a first wavelength conversion layer with wavelength converting properties such that electromagnetic radiation of a first wavelength range is converted into electromagnetic radiation of a second wavelength range, structuring of the first wavelength conversion layer into first regions and second regions, wherein the wavelength converting properties of the first wavelength conversion layer are impaired or removed in the first regions after structuring.

Claims

1. A method for producing a structured wavelength conversion layer, the method comprising: providing a first wavelength conversion layer with wavelength converting properties such that electromagnetic radiation of a first wavelength range is converted into electromagnetic radiation of a second wavelength range; and structuring of the first wavelength conversion layer into first regions and second regions, wherein the wavelength converting properties of the first wavelength conversion layer are impaired or removed in the first regions after structuring.

2. The method according to claim 1, wherein the first wavelength conversion layer comprises nanoparticles.

3. The method according to claim 2, wherein the nanoparticles are quantum dots.

4. The method according to claim 3, wherein an ability of the quantum dots to absorb electromagnetic radiation is impaired or removed in the first regions after the structuring of the first wavelength conversion layer.

5. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises changing a composition of the first wavelength conversion layer in the first regions.

6. The method according to claim 5, wherein structuring of the first wavelength conversion layer comprises applying a protective mask on the first wavelength conversion layer, and patterning the protective mask to generate the first regions and the second regions.

7. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises changing a composition of the first wavelength conversion layer in the first regions by oxidation processes.

8. The method according to claim 7, further comprising removing a protective mask after the composition of the first wavelength conversion layer is changed in the first regions.

9. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises treating the first regions with UV radiation.

10. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises treating the first regions with at least one of the following substances: O.sub.2, O.sub.3, H.sub.2O.sub.2, or N.sub.2O.

11. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises performing aqueous redox chemistry in the first regions.

12. The method according to claim 1, wherein structuring of the first wavelength conversion layer comprises performing non-aqueous redox chemistry in the first regions.

13. The method according to claim 1, further comprising applying a protective layer on the first wavelength conversion layer after structuring of the first wavelength conversion layer.

14. The method according to claim 13, wherein the protective layer penetrates into the first wavelength conversion layer.

15. The method according to claim 1 further comprising: providing a second wavelength conversion layer on the first wavelength conversion layer; and structuring of the second wavelength conversion layer into third regions and fourth regions, wherein the second wavelength conversion layer has wavelength conversion properties such that the electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of a third wavelength range, and wherein the wavelength converting properties of the second wavelength conversion layer are impaired or removed in the third regions after structuring.

16. An optoelectronic device comprising: a light-emitting semiconductor chip; and a first wavelength conversion layer with wavelength converting properties such that electromagnetic radiation of a first wavelength range is converted into electromagnetic radiation of a second wavelength range, wherein the first wavelength conversion layer comprises first regions and second regions, wherein the wavelength converting properties of the first wavelength conversion layer are impaired or removed in the first regions.

17. The optoelectronic device according to claim 16, wherein the first wavelength conversion layer comprises nanoparticles.

18. The optoelectronic device according to claim 16, wherein the first wavelength range is between 430 nanometers and 490 nanometers, inclusive, and wherein the second wavelength range is between 600 nanometers and 800 nanometers, inclusive.

19. The optoelectronic device according to claim 16, further comprising a protective layer arranged on a side of the first wavelength conversion layer facing away from the light-emitting semiconductor chip.

20. The optoelectronic device according to claim 16, further comprising a second wavelength conversion layer with wavelength converting properties such that electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of a third wavelength range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Advantageous embodiments and developments of the method for producing a structured wavelength conversion layer and the optoelectronic device will become apparent from the exemplary embodiments described below in conjunction with the figures.

[0065] FIGS. 1A to 1E show steps of a method for producing a structured wavelength conversion layer according to one exemplary embodiment by means of schematic illustrations;

[0066] FIGS. 2A to 2F show steps of a method for producing a structured wavelength conversion layer according to another exemplary embodiment by means of schematic illustrations; and

[0067] FIG. 3 shows wavelength conversion layers with different compositions.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0068] 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 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.

[0069] In FIG. 1A a first wavelength conversion layer 2 is provided, for example on a light-emitting semiconductor chip 1. The first wavelength conversion layer 2 comprises quantum dots, in particular CdS quantum dots encapsulated with ZnS. The first wavelength conversion layer 2 is designed to convert electromagnetic radiation of a first wavelength range, for example the blue wavelength range of the visible electromagnetic radiation, into electromagnetic radiation of a second wavelength, for example the red wavelength range of the visible electromagnetic radiation. In other words, the wavelength conversion layer 2 comprises wavelength conversion properties. The light-emitting semiconductor chip 2 is designed to emit electromagnetic radiation of the first wavelength range.

[0070] After the first wavelength conversion layer 2 is provided, the first wavelength conversion layer 2 is structured into first regions 4 and second regions 5. This can be achieved by applying a protective mask 3 on the first wavelength conversion layer 2. The protective mask 3 is only applied on the second regions 5. In other words, the first regions 4 are free of the protective mask 3.

[0071] The composition of the first wavelength conversion layer 2 is changed by treating the first regions 4 with UV radiation, oxygen and moisture. In other words, aqueous redox chemistry is performed in the first regions aided by irradiation with UV radiation. Due to this treatment, the quantum dots in the first wavelength conversion layer 2 change their composition. For example, CdS is oxidized to CdSO.sub.4.

[0072] In the first regions 4, an ability of the quantum dots to absorb the electromagnetic radiation of the first wavelength range is impaired or removed. In other words, the quantum dots stop absorbing electromagnetic radiation of the first wavelength range.

[0073] FIG. 1B illustrates a state wherein the wavelength conversion layer 2 shows a reduced ability to absorb the electromagnetic radiation of the first wavelength range in the first regions 4 compared to the second regions 5. The wavelength conversion properties of the wavelength conversion layer 2 are impaired in the first regions 4, but not in the second regions 5.

[0074] In FIG. 1C, the wavelength conversion properties of the wavelength conversion layer 2 are removed in the first regions 4. The quantum dots in the first regions 4 do not longer absorb electromagnetic radiation of the first wavelength range. In other words, the first regions 4 are transparent for the electromagnetic radiation of the first wavelength range.

[0075] After the composition of the first wavelength conversion layer 2 is changed, the protective mask 3 is removed (FIG. 1D). This reveals the whole 1st wavelength conversion layer 2. As no material is removed during the structuring of the first wavelength conversion layer 2, the first wavelength conversion layer 2 is still continuous. The first wavelength conversion layer 2 has preferably a plane surface. In particular, the moisture used to change the composition of the first wavelength conversion layout 2 in the first regions 4 is removed by heating or under reduced pressure.

[0076] As shown in FIG. 1E, a protective layer 6 is applied on the first wavelength conversion layer 2, preferably by ALD. For example, the protective layer 6 comprises Al.sub.2O.sub.3. The protective layer 6 prevents a degradation of the 1st wavelength conversion layer 2 which can be caused by a combination of moisture and electromagnetic radiation. In particular, the protective layer 6 is applied on a surface facing away from the light-emitting semiconductor chip 1. Preferably, the protective layer 6 convers the whole surface of the first wavelength conversion layer 2 facing away from the light-emitting semiconductor chip 1. The protective layer 6 may penetrate into the first wavelength conversion layer 2.

[0077] In combination with FIG. 1E also an optoelectronic device 7 is described. The optoelectronic device comprises the light-emitting semiconductor chip 1 and the wavelength conversion layer 2 that is structured into first regions 4 and second regions 5. In the first regions 4, the wavelength conversion layer 2 has an at least impaired ability to convert electromagnetic radiation of the first wavelength range into the second wavelength range. Thus, in the first regions 4, the optoelectronic device 7 emits electromagnetic radiation of the first wavelength range. In the second regions 5 of the first wavelength conversion layer 2, the electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of the second wavelength range by the quantum dots present in the first wavelength conversion layer 2. The optoelectronic device 7 emits electromagnetic radiation of the first wavelength range and electromagnetic radiation of the second wavelength range in different regions. For example, the optoelectronic device 7 emits electromagnetic radiation in the blue and the red wavelength range of the visible electromagnetic radiation.

[0078] In particular, the first regions 4 and the second regions 5 have the same extent and shape. Alternatively, the second regions 5 may be smaller than the first regions 4. Such a configuration is shown in FIG. 2A.

[0079] A second wavelength conversion layer 8 is applied on the first wavelength conversion layer 2, preferably above the protective layer 6 (FIG. 2B). The second wavelength conversion layer 8 comprises wavelength conversion properties such that electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of a third wavelength range. The third wavelength range can be the green wavelength range of the visible electromagnetic radiation. In particular, the second wavelength conversion layer 8 comprises quantum dots differing in size and/or composition from the quantum dots of the first wavelength conversion layer 2.

[0080] For structuring the second wavelength conversion layer 8 into third regions 9 and fourth regions 10, a protective mask 3 is applied on the second wavelength conversion layer, as shown in FIG. 2C. The protective mask 3 covers only the fourth regions 10. The third regions 9 are free of the protective mask 3.

[0081] During structuring of the second wavelength conversion layer 8, the composition of the second wavelength conversion layer 8 is changed in the third regions 9 (FIG. 2D). The protective mask 3 prevents the change in composition in the fourth regions 10. Due to the change of composition, the wavelength conversion properties of the second wavelength conversion layer 8 are impaired or removed. For example, during structuring of the second wavelength conversion layer 8, non-aqueous redox chemistry is performed in the third regions 9. No material is removed from the second wavelength conversion layer 8 during structuring. In other words, the second wavelength conversion layer 8 stays mechanically intact.

[0082] After the composition of the second wavelength conversion layer 8 is changed in the third regions 9, the protective mask 3 is removed, as shown in FIG. 2E.

[0083] Then a further protective layer 11 is applied on the second wavelength conversion layer 8 on the side facing away from the first wavelength conversion layer 2 (FIG. 2F). The further protective layer 11 is designed to protect the second wavelength conversion layer 8 from external influences, like moisture. The further protective layer 11 can be a single layer or are layer stack. For example, the further protective layer 11 comprises Al.sub.2O.sub.3 and/or TiO.sub.2. The further protective layer can penetrate the second wavelength conversion layer 8.

[0084] FIG. 2F also shows a further exemplary embodiment of an optoelectronic device 7. The optoelectronic device 7 presently comprises a light-emitting semiconductor chip designed to emit electromagnetic radiation of the first wavelength range as well as a first wavelength conversion layer 2 and a second wavelength conversion layer 8. Compared to the optoelectronic device 7 of FIG. 1E, the present optoelectronic device 7 comprises an additional wavelength conversion layer.

[0085] The first wavelength conversion layer 2 shows conversion properties such that electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of the second wavelength range. The second wavelength conversion layer 8 shows wavelength conversion properties such that electromagnetic radiation of the first wavelength range is converted into electromagnetic radiation of the third wavelength range. Above each wavelength conversion layer a protective layer 6, 11 is arranged. In particular, a protective layer 6 is arranged between the first wavelength conversion layer 2 and the second wavelength conversion layer 8.

[0086] The first wavelength conversion layer 2 comprises first regions 4 and second regions 5. The second wavelength conversion layer 8 comprises third regions 9 and fourth regions 10. The second regions 5 are covered by the third regions 9, whereas the first regions 4 are covered by the third regions 9 and the fourth regions 10. In other words, the fourth regions 10 are arranged above the first regions 4 and the third regions 9 are arranged above the first regions 4 and the second regions 10. In particular, the size of the first and the third regions is bigger than the size of the second and the fourth regions.

[0087] The optoelectronic device 7 of FIG. 2F is able to emit electromagnetic radiation of the first, the second and the third wavelength range. Areas in which the light-emitting semiconductor chip 1 is covered by the second regions 5 of the first wavelength conversion layer 2 and by the third regions 9 of the second wavelength conversion layer 8 emit electromagnetic radiation of the second wavelength range. Areas in which the light-emitting semiconductor chip 1 is covered by the first regions 4 of the first wavelength conversion layer 2 and by the third regions 9 of the second wavelength conversion layer 8 emit electromagnetic radiation of the first wavelength range. Areas in which the light-emitting semiconductor chip 1 is covered by the first regions 4 of the first wavelength conversion layer 2 and by the fourth regions 10 of the second wavelength conversion layer 8 emit electromagnetic radiation of the third wavelength range.

[0088] FIG. 3 shows three samples of wavelength conversion layers comprising different compositions. The wavelength conversion layers comprise quantum dots. The samples have been subjected to elevated temperature, moisture and blue light for increasingly longer period from left to right.

[0089] In sample S1, most of the quantum dots still have their original composition. Thus, the converting properties of the conversion layer of this sample are unaffected. The quantum dots are still able to convert electromagnetic radiation.

[0090] In sample S2, the wavelength converting properties of the wavelength conversion layer is already impaired. This can be explained as the composition of the wavelength conversion layer has changed due to the treatment with temperature, moisture and blue light.

[0091] In sample S3, the wavelength converting properties of the wavelength conversion layer are removed. The quantum dots in this particular wavelength conversion layer have completely changed their composition and thus are no longer able to absorb electromagnetic radiation. The wavelength conversion layer is completely transparent.

[0092] The features and exemplary embodiments described in connection with the figures can 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.

[0093] 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.