Fabrication process of monolithic RGB array

Abstract

1. A method of forming a multicolor light emitting array, the method comprising: providing a first light emitting device configured to emit light having a first dominant peak wavelength and a second light emitting device configured to emit light having the first dominant peak wavelength; forming a color conversion region at least partially associated with the first light emitting device and the second light emitting device, the color conversion region configured to absorb light having the first dominant peak wavelength and emit light having a second dominant peak wavelength longer than the first dominant peak wavelength; and photobleaching a portion of the color conversion region associated with the first light emitting device so that the color conversion region associated with the first light emitting device at least partially transmits light having the first dominant peak wavelength, thereby enabling light having the first dominant peak wavelength to be emitted by a first pixel associated with the first light emitting device and light having the second dominant peak wavelength to be emitted by a second pixel associated with the second light emitting device.

Description

[Technical Field]

[0001] The present invention relates to arrays of light emitting diodes (LEDs) and methods of forming LED arrays. In particular, but not exclusively, the present invention relates to multicolor monolithic arrays of light emitting diodes using downconverting organic semiconductors and methods of forming multicolor monolithic arrays of light emitting diodes using downconverting organic semiconductors. [Background technology]

[0002] Light-emitting diode (LED) devices have proven to provide efficient light sources for a wide range of applications. Increased LED light generation efficiency and extraction, along with the fabrication of smaller LEDs (smaller light-emitting surface area) and the integration of LED emitters of different wavelengths into arrays, have led to the provision of high-quality color arrays that have many applications, particularly in display technology.

[0003] To provide high-resolution LED arrays, such as microLED arrays, the emitting surface area defining the pixel surface, as well as the pixel pitch, has become smaller compared to the emitting surface of conventional LEDs. However, to provide arrays with higher resolution, the pixel pitch in such arrays has been reduced to very small pitches (e.g., less than 5 μm), which presents several challenges. For example, to achieve full-color red-green-blue (RGB) displays, quantum dots (QDs) are typically used as color conversion regions, and blue LEDs are typically used as the input light source. Such QDs are typically used to convert blue input light into red and green light using appropriate QDs. However, the thickness of such QD layers generally needs to be on the order of 20 μm to 30 μm to achieve full color saturation. Therefore, the smallest pixels that can be fabricated at these thicknesses are limited to widths greater than 20 μm. Summary of the Invention [Problem to be solved by the invention]

[0004] Processing QDs for light wavelength color conversion in micro LED arrays, for example, using photolithography and inkjet printing to form layers of materials containing QDs, has been found to introduce additional problems, such as reduced efficiency and lifetime of the wavelength-converting QDs, thus posing significant challenges in the pursuit of high-resolution micro LED arrays where it is beneficial to have a pixel pitch of less than 10 μm. [Means for solving the problem]

[0005] To alleviate at least some of the above problems, there is provided a light emitting diode array having a plurality of light emitting pixels and a method for forming a light emitting diode array including a plurality of light emitting pixels according to the appended claims.

[0006] A method of forming a multicolor light emitting array is provided, the method including providing a first light emitting device configured to emit light having a first dominant peak wavelength and a second light emitting device configured to emit light having the first dominant peak wavelength; forming a color conversion region at least partially associated with the first light emitting device and the second light emitting device, the color conversion region configured to absorb light having the first dominant peak wavelength and emit light having a second dominant peak wavelength longer than the first dominant peak wavelength; and forming a color conversion region associated with the first light emitting device such that the color conversion region associated with the first light emitting device at least partially transmits light having the first dominant peak wavelength, thereby enabling light having the first dominant peak wavelength to be emitted by a first pixel associated with the first light emitting device and light having the second dominant peak wavelength to be emitted by a second pixel associated with the second light emitting device. and photobleaching a portion of the color conversion region.

[0007] A multicolor light-emitting array is also provided, the multicolor light-emitting array comprising: a first pixel associated with a first light-emitting device and a second pixel associated with a second light-emitting device, wherein the first light-emitting device is configured to emit light having a first dominant peak wavelength and the second light-emitting device is configured to emit light having the first dominant peak wavelength; and a color conversion region at least partially associated with the first light-emitting device and the second light-emitting device, the color conversion region configured to absorb light having the first dominant peak wavelength and emit light having a second dominant peak wavelength that is longer than the first dominant peak wavelength, wherein a portion of the color conversion region associated with the first light-emitting device is photobleached such that the color conversion region associated with the first light-emitting device at least partially transmits light having the first dominant peak wavelength, thereby enabling light having the first dominant peak wavelength to be emitted by the first pixel and light having the second dominant peak wavelength to be emitted by the second pixel.

[0008] Advantageously, the combination of forming color conversion regions and photobleaching provides an efficient and effective method of colorizing the light output from light emitting devices that emit the same dominant peak wavelength such that the resulting array emits light having different wavelengths.

[0009] Preferably, the method includes providing a third light emitting device configured to emit light having a first dominant peak wavelength, the third light emitting device being a color conversion region at least partially associated with the third light emitting device; photobleaching a portion of the color conversion region associated with the third light emitting device such that the color conversion region associated with the third light emitting device at least partially transmits light having the first dominant peak wavelength; and forming a further color conversion region at least partially associated with the first light emitting device, the second light emitting device, and the third light emitting device, the further color conversion region having a second dominant peak wavelength. and forming a color conversion region associated with the first light emitting device, the color conversion region being configured to at least partially transmit light, absorb light having a first dominant peak wavelength, and emit light having a third dominant peak wavelength longer than the first dominant peak wavelength; and photobleaching a portion of the color conversion region associated with the first light emitting device so that the color conversion region associated with the first light emitting device transmits light having the first dominant peak wavelength, thereby enabling light having the first dominant peak wavelength to be emitted by a first pixel, light having the second dominant peak wavelength to be emitted by a second pixel, and light having the third dominant peak wavelength to be emitted by a third pixel associated with the third light emitting device. Advantageously, the process can be used to provide light emitted at a plurality of different dominant peak wavelengths. Advantageously, a red-green-blue array can be produced, enabling a full-color, high-resolution display.

[0010] Preferably, the photobleaching is carried out at a wavelength of 340 nm to 460 nm and at 5 W / cm 2 More than 10 W / cm, preferably at least 10 W / cm 2 and irradiating the color conversion region and / or further color conversion region with light having an irradiance of 1000 .ANG. / 2 ...

[0011] Preferably, the light emitting device is part of a monolithic array, preferably the monolithic array is a high resolution micro LED array. Preferably, the monolithic array comprises a plurality of epitaxial crystalline semiconductor layers, preferably the epitaxial crystalline semiconductor layers comprise III-V compound semiconductor materials. Advantageously, known techniques for providing high quality efficient LED devices can be used, and the wavelength of the device can be controlled by adjusting the color conversion material and the photobleaching material. It can be changed by combining it with reach.

[0012] Preferably, the color conversion region and / or the further color conversion region comprises an organic semiconductor configured to absorb light having a first dominant peak wavelength and re-emit light having a different dominant peak wavelength. Advantageously, organic semiconductors provide efficient down-conversion, allowing the use of thinner films and facilitating higher resolution arrays of light-emitting pixels.

[0013] Preferably, the organic semiconductor is a conjugated organic semiconductor, and preferably the conjugated organic semiconductor is dispersed in the light-limiting material. Advantageously, such organic semiconductors can be deposited using spin / slit coating techniques and can be processed using known techniques compatible with LED array production.

[0014] Preferably, the colour conversion region is arranged to emit light having a dominant peak wavelength corresponding to red. Preferably, the further colour conversion region is arranged to emit light having a dominant peak wavelength corresponding to green. Advantageously, a full colour display is provided.

[0015] Preferably, the color conversion region and / or further color conversion region are layers having a thickness of 500 nm or less. Advantageously, thin layers lend themselves to smaller pixels for higher resolution displays.

[0016] Preferably, the method comprises depositing the organic semiconductor in a solvent, typically an organic solvent such as an alkene, alkane, or mixture thereof; preferably, the concentration of the organic semiconductor in the solvent is 1-5 wt %, more typically 2.5 wt %, and more preferably, the solvent comprises toluene and heptane. Preferably, forming the color conversion region and / or further color conversion region comprises spin coating or slit coating. Advantageously, the color conversion region is formed efficiently and can be integrated into known processing steps.

[0017] Further aspects of the invention will become apparent from the description and the appended claims.

[0018] A detailed description of embodiments of the present invention will now be described, by way of example, with reference to the figures. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows a cross-sectional view of a portion of an array of light-emitting devices. [Figure 2] 2 shows a cross-sectional view of a portion of the array of light emitting devices of FIG. 1 that has been processed. [Figure 3] 3 shows a cross-sectional view of photobleaching of a treated portion of the array of light-emitting devices of FIG. 2. [Figure 4] 4 shows a cross-sectional view of a portion of the array of light emitting devices of FIG. 3 that has been processed. [Figure 5] 5 shows a cross-sectional view of photobleaching of a treated portion of the array of light-emitting devices of FIG. 4. [Figure 6] A series of syntheses of down-converting organic semiconductor materials is presented. DETAILED DESCRIPTION OF THE INVENTION

[0020] A sophisticated process for providing multicolor light-emitting arrays, such as high-resolution micro light-emitting diode arrays, is described with reference to Figures 1-6. Advantageously, the process combines the application of a coating color conversion material to an array of light-emitting devices and selective photobleaching of the color conversion material to provide an efficient and commercially viable process for colorizing the array. Such a process advantageously enables the fabrication of multicolor high-resolution micro LED arrays, for example, micro LED arrays having pixel pitches on the order of 1 μm.

[0021] The color conversion materials described herein down-convert light having certain wavelengths to produce more Color conversion materials are materials that can be used to provide light of longer wavelengths than blue (approximately 450 nm) or UV light. For example, blue light (approximately 450 nm) or UV light can be downconverted by absorption and emission by a color conversion material to provide light having green (approximately 540 nm) and / or red (approximately 630 nm) wavelengths. Advantageously, color conversion materials can be used to provide light emission at a wavelength different from an array of light emitting devices emitting at one wavelength (e.g., a blue-emitting array of LED devices), thereby utilizing known methods for producing high-quality, high-efficiency light emitting arrays.

[0022] Color conversion materials containing a medium in which an organic semiconductor is dispersed are known to downconvert short-wavelength (high-energy) light to provide long-wavelength (low-energy) light. It has been found that downconverting organic semiconductors can be tailored to achieve targeted physical properties. In particular, organic semiconductors can advantageously achieve specific values ​​of ionization potential or electron affinity, absorption and emission properties, charge transport properties, phase behavior, solubility, and processability. Typically, organic semiconductors are conjugated organic semiconductors containing multiple conjugated structures. In one example, such conjugated structures include a core and arms. The functions of these components of the organic semiconductor can be tailored to provide specific properties.

[0023] Macromolecules are discussed, for example, in Acc. Chem. Res 2019, 52, 1665-1674 and J. Mater. Chem. C, 2016, 11499, the contents of which are incorporated by reference in their entirety. Tunable macromolecules include conjugated organic semiconductors containing multiple conjugated structures. These are typically organic semiconductors. Such structures can be formed to include a core and arms. Multiple conjugated structures can be formed to have different functional properties, such as different absorption and / or emission properties. An example of a conjugated structure is the TPA-BDI (triphenylamine-benzodiimidazole) molecular species, which is an organic system with a benzodiimidazole core that can be prepared from commercially available starting materials. Benzodiimidazoles and their derivatives have tunable optical properties through the use of push-pull donor-acceptor moieties.

[0024] The photochemical stability of materials, such as organic semiconductors, is an important factor in determining their suitability for various applications. Such photochemical stability reflects their ability to undergo cycles of excitation and relaxation to a dark ground state without irreversible damage. Photobleaching occurs when there is irreversible damage to the original optical properties, e.g., "Photobleaching of organic fluorophores: quantitative characterization, mechanisms, and protection," Methods and Applications in Fluorescence, 2020, Volume 10, https: / / doi.org / 10.1038 / s10240-019-0180-1 8, Number 2, which is incorporated by reference in its entirety. Photobleaching of organic semiconductors, such as conjugated polymer structures, is generally considered undesirable because it deprives the organic semiconductor of the functionality for which it was originally designed.

[0025] Advantageously, a process is described herein that enables colorization of arrays of light-emitting devices, such as monolithic nitride-based blue-emitting high-resolution arrays, by selective photobleaching of layers of down-converting macromolecules.

[0026] FIG. 1 illustrates a cross-sectional view of a portion of an array of light emitting devices 100, which is a monolithic light emitting diode (LED) array 100. A gallium nitride (GaN) based layer 102 is shown on which three light emitting diode (LED) devices 104, 106, and 108 are formed. The first LED device 104 is configured to emit light having a dominant peak wavelength corresponding to blue. The second LED device 106 is configured to emit light having a dominant peak wavelength corresponding to blue. The third LED device 108 is configured to emit light having a dominant peak wavelength corresponding to blue. The three LED devices 104, 106, and 108 is shown without electrical connections to facilitate carrier injection through the p-type and n-type regions to provide emissive recombination, and those skilled in the art will appreciate that such electrical connections for carrier injection through the p-type and n-type regions in an LED device may be implemented in a variety of ways. For example, the monolithic LED array 100 may be coupled with a complementary metal-oxide-semiconductor (CMOS) backplane to control the emission from the individual LED devices.

[0027] Although the LED devices 104, 106, 108 are shown in a particular configuration within the array 100, those skilled in the art will appreciate that alternative and / or additional configurations and embodiments of LED devices may be used in combination with the further features described herein. Although only three LED devices 104, 106, 108 are shown in cross section, in further examples, any suitable number of LED devices may be used to form the array 100.

[0028] The LED devices 104, 106, and 108 are provided as part of a monolithic array 100 of light-emitting devices. Also shown are regions 110 provided between each LED device 104, 106, and 108, which are used to reduce optical crosstalk between the individual light-emitting diode devices 104, 106, and 108. Reducing optical crosstalk between LED devices in the array improves the distinction between the colors of light emitted by each LED device and its associated pixel. Regions 110 are metallic regions. Beneficially, the use of reflective regions, such as metallic regions, reduces light absorption in certain directions and reuses reflected light if emitted in those specific directions (e.g., directions that do not result in emission through the light-emitting surface associated with the pixel). In further examples, alternative and / or additional materials are used to form regions 110. While regions 110 are shown in FIG. 1 through the GaN-based region 102, any suitable configuration of regions 110 may be used. In further examples, additional layers, such as a substrate layer and a CMOS backplane layer, may be implemented, although these layers are not shown in FIG. 1.

[0029] The array of LED devices 104, 106, 108 is formed to provide a selectively addressable LED device configured to emit light having a dominant peak wavelength of light corresponding to blue light. Although three LED devices 104, 106, 108 are shown, those skilled in the art will appreciate that in further examples, a different number of alternative and / or additional light emitting diode devices may be provided.

[0030] The LED devices 104, 106, 108 are nitride-based epitaxially grown compound crystalline semiconductor LEDs 104, 106, 108. In further examples, other LEDs, such as other III-V or II-VI compound semiconductor materials, are used. Advantageously, the LED devices 104, 106, 108 are grown monolithically, thereby providing high-quality materials with excellent uniformity and efficiency without the need for transfer of individual LED devices. Advantageously, the monolithic LED array is coupled to a backplane (not shown) to enable control of the individual LED devices 104, 106, 108 within the monolithic array. The LED devices 104, 106, 108 are grown as part of the monolithic array of LEDs using metal-organic chemical vapor deposition (MOCVD). In further examples, alternative and / or additional techniques, such as molecular beam epitaxy (MBE) and other suitable deposition / growth techniques, are used to form the LED devices 104, 106, 108 as part of the monolithic array. In further examples, other additional and / or alternative semiconductor fabrication and processing techniques are used to provide a monolithic array of LED devices 104, 108, 108. In further examples, alternatively and / or additionally, array 100 is formed from individual LED devices that are not part of a monolithic array.

[0031] Once an array 100 of LED devices 104, 106, 108 is provided as described with respect to FIG. 1, the array 100 is processed as shown in FIG.

[0032] FIG. 2 shows a cross-sectional view of a portion of the array 100 of light-emitting diode devices of FIG. 1 that has been processed to provide a processed array 200 including a color conversion region 202. The color conversion region 202 is a layer including an organic semiconductor material configured to absorb light having a dominant peak wavelength corresponding to blue light and emit light having a dominant peak wavelength corresponding to red light. The color conversion region 202 has a thickness of 500 nm. The color conversion region 202 includes an organic semiconductor that converts blue light to red light at a 2.5% concentration by weight in a solvent. The solvent is made of 50% toluene and 50% heptane. In further examples, the color conversion region 202 has a different thickness and / or a different composition. For example, the color conversion region 202 has a thickness that converts substantially all of the input light from the LED device 108 to provide downconverted red light in the resulting pixel associated with the LED device 108 without the need to filter the blue light. In one example, the organic semiconductor material providing the color conversion function is the synthetic TPA-BDI (triphenylamine-benzodiimidazole) molecular species, an organic system with a benzodiimidazole core. Such materials can be prepared from commercially available starting materials. Benzodiimidazoles and their derivatives have tunable optical properties through the use of push-pull donor-acceptor moieties. In one example, in a down-converting hybrid LED device, TPA-BDI is incorporated into an optically transparent material, such as a poly(urethane) resin, as a host and encapsulant.

[0033] FIG. 6 shows how, in one example, TPA-BDI is synthesized in four steps from 1,5-difluoro-2,4-dinitrobenzene, shown as the first compound 502 in FIG. 6 . The SNAr reaction of the first compound 502 with isobutylamine is shown, which provides the second compound 504 in high yield (e.g., 90%). Subsequent reduction of the nitro group of the second compound 504 provides the third compound 506, and condensation of the third compound with 5-bromo-2-thiophenecarbaldehyde provides the key fourth intermediate compound 508 in approximately 47% yield over two steps. The final material, TPA-BDI 510, is obtained in moderate yield (e.g., 55%) through Suzuki-Miyaura cross-coupling of the fourth compound 508 with 4-(diphenylamino)phenylboronic acid pinacol ester, thereby providing TPA-BDI 510. In one example, the organic semiconductor material is benzodiimidazole and its derivatives, although in further examples, alternative and / or additional organic semiconductor materials that provide light conversion functionality are used in color conversion region 202 .

[0034] In a further example, the organic semiconductor macromolecule is based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY), e.g., the macromolecule comprises a BODIPY core. In a further example, the macromolecule is based on an electron-deficient 2,1,3-benzothiadiazole (BT) core or the corresponding dimer, in parallel with fluorine and / or triphenylamine donor arms. For example, the macromolecule comprises (TPA-Flu)2BT and (TPA-Flu)2BTBT.

[0035] Advantageously, conjugated macromolecules formed from organic semiconductors can achieve full color saturation within very thin films, typically on the order of submicrons, without the need for additional blue-blocking filters, which would be used if a significant amount of blue input light were not converted / absorbed by the color conversion material. In contrast, for organic semiconductor materials such as conjugated macromolecules, quantum dot thin films require thicknesses of over 20 μm to achieve similar color saturation performance. Beneficially, full color saturation within thin films allows the macromolecules to define pixels with a smaller pitch than conventional quantum dot thin films. Furthermore, advantageously, the use of thin color conversion regions leads to much higher efficiency than conventional quantum dots due to reduced reabsorption.

[0036] The ability to tailor the macromolecules allows for complete dissolution within the photodefinable material, allowing the use of standard semiconductor processing techniques. Utilizing existing techniques allows for economical bulk processing. In contrast, quantum dots suffer from increased degradation in the photodefinable medium. There is a tendency for this to happen.

[0037] Once the color conversion region 202 is provided as illustrated in FIG. 2 , the process moves to the process described with respect to FIG. 3 . FIG. 3 illustrates a cross-sectional view of photobleaching the processed array 200 to provide a partially photobleached array 300. To photobleach the processed array 200, a mask 304 is used to selectively cover portions of the array 200 of light emitting devices. As illustrated with reference to FIG. 3 , the mask 304 is used to cover the third light emitting diode device 108 and portions of the color conversion region 202 thereon. The first light emitting device 104 and the second light emitting diode device 106 are not covered by the mask 204. The mask 304 is a hard mask formed using known techniques. In a further example, the mask 304 is patterned on the surface of the color conversion region 202 using known lithography techniques and is subsequently removed after the color conversion region 202 is illuminated as described below.

[0038] Each of the light emitting diode devices 104, 106, 108 has a portion of an associated color conversion region 202. The mask 304 is illuminated with radiation 306 such that the color conversion regions 202 associated with the first light emitting diode device 104 and the second light emitting diode device 106 receive the radiation 306, while the color conversion region 202 associated with the third light emitting diode device 108 does not receive the radiation. Thus, upon illumination of the selectively masked array, exposed portions 302 of the color conversion regions 202 receive the radiation 306, and masked portions of the color conversion regions 202 are shielded from the radiation 306 by the mask 304.

[0039] The conditions under which the array of light emitting devices is subjected to radiation 306 result in a change in the portions 302 of the color conversion region 202 associated with the first and second light emitting diode devices 104, 106. The portions 302 of the color conversion region 202 associated with the first and second light emitting diode devices 104, 106 are illuminated to provide photobleached portions 302 of the color conversion region 202. Radiation 306 having a wavelength substantially between 340 nm and 460 nm is used to photobleach the portions 302 of the color conversion region 202. The intensity of radiation 306 is 10 W / cm. 2 That's it. The photobleaching process is carried out at a temperature of approximately 80° C. In a further example, different conditions are used to irreversibly change the optical properties of the color conversion region 202 so that only the masked portions provide down-conversion of the input light, while the photobleached portions 302 transmit the input light from the associated LED.

[0040] Once photobleached, the photobleached portion 302 is formed to include the same organic semiconductor material as the non-photobleached portion of the color conversion region 202, but it no longer absorbs light having a first dominant peak wavelength corresponding to blue light and instead emits downconverted blue light having a dominant peak wavelength corresponding to red light. Rather, the photobleached portion 302 of the color conversion region 202 transmits light having a first dominant peak wavelength corresponding to the blue light emitted from the light emitting diode devices 104, 106. The color conversion region 202 associated with the third light emitting diode device 108 continues to function by absorbing blue light and emitting red light. Once the color conversion region 202 has been processed to provide the photobleached portion 302 and non-photobleached portion associated with the third light emitting diode device 108, the process moves to the process described with reference to FIG. 4 .

[0041] Note that while FIG. 3 shows photobleaching of the color conversion region associated with two of the three LED devices, in further examples, any number of LED devices in the array may be covered using a mask, such as mask 304 of FIG. 3, to enable selective photobleaching of color conversion region 202 such that the photobleached areas of color conversion region 202 are irreversibly altered to no longer absorb and downconvert light from the associated LED devices.

[0042] FIG. 4 further illustrates a method for providing a processed array 400 having an additional color conversion region 402. 3 shows a cross-sectional view of the processed array 300 of FIG. 300. The additional color conversion region 402 has a thickness of 500 nm. In a further example, the additional color conversion region 402 alternatively and / or additionally has a different thickness. The additional color conversion region 402 is configured to absorb light having a dominant peak wavelength corresponding to blue light emitted by the light emitting diode devices 104, 106, 108 of the light emitting diode device array and emit light having a dominant peak wavelength corresponding to green light. The additional color conversion region 402 has a weight concentration of organic semiconductor in a solvent of 2.5% organic semiconductor. The solvent is made of 50% toluene and 50% heptane. In a further example, the color conversion region 202 has a different thickness and / or a different composition. The additional color conversion region 402 is provided by slit coating or spin coating. In a further example, alternative and / or additional techniques are used to deposit / form the additional color conversion region 402 on the processed array 400. In one example, the organic semiconductor material providing the color conversion function is a synthetic TPA-BDI molecular species, which is an organic system with a benzodiimidazole core. Such materials can be prepared from commercially available starting materials. Benzodiimidazoles and their derivatives have tunable optical properties through the use of push-pull donor-acceptor moieties. In one example, in a down-converting hybrid LED device, TPA-BDI is incorporated into an optically transparent material, such as a poly(urethane) resin, as the host and encapsulant. While a transparent poly(urethane) resin is used as the host and encapsulant, in a further example, the organic semiconductor material is dispersed in a different medium.

[0043] FIG. 6 shows how, in one example, TPA-BDI is synthesized in four steps from 1,5-difluoro-2,4-dinitrobenzene, shown as the first compound 502 in FIG. 6 . The SNAr reaction of the first compound 502 with isobutylamine is shown, which provides the second compound 504 in high yield (e.g., 90%). Subsequent reduction of the nitro group of the second compound 504 provides the third compound 506, and condensation of the third compound with 5-bromo-2-thiophenecarbaldehyde provides the key fourth intermediate compound 508 in approximately 47% yield over two steps. The final material, TPA-BDI 510, is obtained in moderate yield (e.g., 55%) through Suzuki-Miyaura cross-coupling of the fourth compound 508 with 4-(diphenylamino)phenylboronic acid pinacol ester, thereby providing TPA-BDI 510. In one example, the organic semiconductor material is benzodiimidazole and its derivatives, although in further examples, alternative and / or additional organic semiconductor materials that provide light conversion functionality are used in color conversion region 402 .

[0044] In a further example, the organic semiconductor macromolecule is based on 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY), e.g., the macromolecule comprises a BODIPY core. In a further example, the macromolecule is based on an electron-deficient 2,1,3-benzothiadiazole (BT) core or the corresponding dimer, in parallel with fluorine and / or triphenylamine donor arms. For example, the macromolecule comprises (TPA-Flu)2BT and (TPA-Flu)2BTBT.

[0045] Once the additional color conversion regions 402 are provided, the process moves to that described with reference to FIG. 5. FIG. 5 shows a cross-sectional view of a photobleached array 500 of light emitting devices provided by photobleaching the processed array 400 described with reference to FIG. 4. A mask 504 is shown that is selectively used to cover the additional color conversion regions 402 associated with the second light emitting diode devices 106 and the third light emitting devices 108. The mask 504 is a hard mask formed using known techniques. In a further example, the mask 504 is patterned on the surface of the color conversion regions 402 using known lithography techniques and subsequently removed after the color conversion regions 402 are illuminated as described below. The mask 504 is then subjected to radiation 506 under suitable conditions. Radiation 506 having a wavelength substantially between 340 nm and 460 nm is used to photobleach portions 502 of the additional color conversion regions 402. The intensity of the radiation 506 is 10 W / cm. 2 That's it. The photobleaching process is It is performed at a temperature of approximately 80° C. In a further example, different conditions are used to irreversibly change the optical properties of the further color conversion region 402 so that only the masked portions provide down-conversion of the input light.

[0046] Thus, the portion 502 of the further color conversion region 402 associated with the first light emitting diode device 104 is photobleached, and the further color conversion regions 402 associated with the second and third light emitting diode devices 106, 108 are not photobleached.

[0047] The resulting structure is such that light emitted from the first light emitting device 104 is transmitted through both the photobleached portion 302 of the photobleached color conversion region 202 and the photobleached portion 502 of the further color conversion region 402 to provide a photobleached color conversion region portion 302 and a photobleached further color conversion region portion 502 associated with the further color conversion region 402. Light emitted from the second light emitting diode device 106 is transmitted through the photobleached portion 302 of the color conversion region 202, absorbed by the further color conversion region 402, where it is downconverted and subsequently emitted as light having a dominant peak wavelength corresponding to green light. Light emitted from the third LED device 108 is absorbed by the color conversion region 202, where it is downconverted to provide red light. The red light is then transmitted through the further color conversion region 402, where it is emitted from the structure 500 as red light. The red light has a longer wavelength than the green light and is not absorbed by the further color conversion region 402 but is instead transmitted through the further color conversion region 402 .

[0048] As a result of selectively photobleaching portions of the color conversion regions 202, 402, there is a light emitting surface associated with each LED 104, 106, 108 that emits light having a different dominant peak wavelength. The light emitting surface associated with the first LED device 104 provides a first pixel that emits blue light, the light emitting surface associated with the second LED device 106 provides a second pixel that emits green light, and the light emitting surface associated with the third LED device 108 provides a third pixel that emits red light. While differences in the cross-sectional widths of the LED devices 104, 106, 108 and the cross-sectional widths of the photobleached and non-photobleached portions of the color conversion regions 202, 402 are shown, in further examples, the arrangement of such features can be adapted to provide pixels of appropriate shape, size, and pitch in a pixel array.

[0049] Thus, a blue-emitting monolithic array of light-emitting devices can be used to provide light at blue, green, and red wavelengths. Although the color conversion is illustrated for three light-emitting diode devices, those skilled in the art will appreciate that the process is applicable to arrays of any number of such devices and to light at other wavelengths.

[0050] The process is a simple and elegant way to colorize arrays of blue-light-emitting diode devices. Advantageously, organic semiconductors dispersed in media such as conjugated polymer macromolecules can achieve full color saturation within very thin films, typically on the order of submicron, without the need for additional blue-blocking filters. Furthermore, full color saturation within thin films allows the macromolecules to define pixels with a smaller pitch than conventional quantum dot thin films. Quantum dot thin films typically require thicknesses in excess of 20 μm to achieve similar color saturation performance.

[0051] An additional benefit of thin films is that the use of thin color conversion layers leads to much higher efficiencies than conventional quantum dots due to less re-absorption.

[0052] Advantageously, the ability to tailor the macromolecules allows for complete dissolution within the photodefinable material, allowing the use of standard semiconductor processing techniques. In contrast, quantum dots tend to suffer from increased degradation in optically confining media.

Claims

1. 1. A method of forming a multicolor light emitting array, comprising: providing a first light emitting device configured to emit light having a first dominant peak wavelength, a second light emitting device configured to emit light having the first dominant peak wavelength, and a third light emitting device configured to emit light having the first dominant peak wavelength; forming a color conversion region over the first light-emitting device, the second light-emitting device, and the third light-emitting device, the color conversion region configured to absorb light having the first dominant peak wavelength and emit light having a second dominant peak wavelength longer than the first dominant peak wavelength; masking a portion of the color conversion region over the third light-emitting device; photobleaching a portion of the color conversion regions on the first light emitting device and the second light emitting device such that the color conversion regions on the first light emitting device and the second light emitting device at least partially transmit light having the first dominant peak wavelength; subsequently, forming a further color conversion region on the color conversion region, the further color conversion region being configured to at least partially transmit light having the second dominant peak wavelength, absorb light having the first dominant peak wavelength, and emit light having a third dominant peak wavelength that is longer than the first dominant peak wavelength and shorter than the second dominant peak wavelength; masking a portion of the further color conversion region over a portion of the color conversion region over the second light emitting device and the third light emitting device, and photobleaching a portion of the further color conversion region over a portion of the color conversion region over the first light emitting device such that the further color conversion region over a portion of the color conversion region over the first light emitting device transmits light having the first dominant peak wavelength, thereby allowing light having the first dominant peak wavelength to be emitted by a first pixel associated with the first light emitting device, light having the third dominant peak wavelength to be emitted by a second pixel associated with the second light emitting device, and light having the second dominant peak wavelength to be emitted by a third pixel associated with the third light emitting device; A method comprising:

2. The photobleaching step includes irradiating the color conversion region and / or the further color conversion region with light having a wavelength of 340 nm to 460 nm and an irradiance of at least 10 W / cm. wherein the temperature of the color conversion region and / or the further color conversion region is 50°C to 110°C.

10. A method for forming the multicolor light-emitting array of claim 1.

3. the light emitting device is part of a monolithic array; 3. A method for forming a multicolor light-emitting array according to claim 1 or 2.

4. the monolithic array includes a plurality of epitaxial crystalline semiconductor layers; 4. A method for forming the multicolor light-emitting array of claim 3.

5. the color conversion region and / or the further color conversion region comprises an organic semiconductor configured to absorb light having the first dominant peak wavelength and re-emit light having a different dominant peak wavelength. A method for forming a multicolor light-emitting array according to any one of claims 1 to 4.

6. The organic semiconductor is a conjugated organic semiconductor.

6. A method for forming a multicolor light-emitting array according to claim 5.

7. the color conversion region is configured to emit light having a dominant peak wavelength corresponding to red; A method for forming a multicolor light-emitting array according to any one of claims 1 to 6.

8. the further color conversion region is configured to emit light having a dominant peak wavelength corresponding to green. A method for forming a multicolor light-emitting array according to any one of claims 1 to 7.

9. the color conversion region and / or the further color conversion region is a layer having a thickness of 500 nm or less; A method for forming a multicolor light-emitting array according to any one of claims 1 to 8.

10. forming the color conversion region and / or the further color conversion region comprises depositing an organic semiconductor in a solvent, wherein the concentration of the organic semiconductor in the solvent is 2.5 wt %; A method for forming a multicolor light-emitting array according to any one of claims 1 to 9.

11. forming the color conversion region and / or the further color conversion region includes spin coating or slit coating; A method for forming a multicolor light-emitting array according to any one of claims 1 to 10.

Images