White light emitting LED structure

Abstract

A white light emitting inorganic light emitting diode (iLED) structure includes first iLEDs electrically connected in series and a second iLED electrically connected to one of the first iLEDs, each first iLED emitting light of a different color than any other first iLED when power is provided to the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs. The second iLED can be electrically connected in series or in parallel with the one of the first iLEDs. Such iLED structures can be used at least for displays, lamps, and indicators.

Description

[0001] Priority Application

[0002] This application claims priority to U.S. Patent Application No. 16 / 888,196, filed May 29, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

[0003] Cross Reference to Related Applications

[0004] Reference is made to U.S. Patent Application Serial No. 16 / 778,948 to Bower et al., entitled “Micro-LED Color Display with Different Current Densities” and U.S. Patent Application Serial No. 16 / 886,625 to Cok et al., entitled “Multi-LED Structures,” the disclosure of each of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0005] The present disclosure relates to white-emitting inorganic light emitting diode circuits and structures for lamps, indicators, and displays. BACKGROUND

[0006] Inorganic light emitting diodes (iLEDs) are used in lamps, indicators, and displays and other applications due to their low cost, efficiency, lifetime, and color purity. In some applications, it is desirable to emit white light. However, individual inorganic light emitting diodes cannot emit white light. In most lighting and indicator applications using iLEDs, white light is achieved by combining an iLED that emits high frequency light, such as blue, with a phosphor or quantum dot that absorbs the high frequency light emitted by the iLED and emits complementary low frequency light, such as yellow. It is also known to provide white light in lamps by connecting red, green, and blue LEDs in series, for example as described in U.S. Patent Publication No. 2009 / 0237925.

[0007] Color displays typically include an array of color pixels. Each color pixel includes sub-pixels that emit different colors of light under the control of a pixel or display controller. Full color displays typically include color pixels with three (or more) emitters (typically red, green, and blue) distributed across the surface of the display, and typically produce a noticeable white light by simultaneously emitting light from each of the different color iLEDs in the color pixel. Some organic light emitting diode (OLED) displays use a common white-emitting emission layer with a color filter to produce color sub-pixels, with a fourth white sub-pixel that emits unfiltered white light. Such RGBW (red, green, blue, white) configurations can reduce the power used by the OLED display, as a large portion of the light from the color pixels is absorbed by the color filter, but the white light is not filtered and thus is emitted more efficiently than the filtered color light (e.g., as discussed in U.S. Patent No. 7,586,497).

[0008] Large format inorganic light emitting diode (iLED) displays are used for outdoor and stadium displays. Because iLEDs are relatively large, e.g., one square millimeter, they are limited to relatively low resolution displays. However, as iLED technology develops, there is increasing interest in applying smaller iLEDs (e.g., micro-LEDs) to displays with higher resolution. For example, U.S. Patent No. 9,818,725, entitled “Large Format Micro-LED Display,” discloses a large format micro-LED display. Inorganic-Light-Emitter Display with Integrated Black Matrix Voltage-Balanced Serial ILED Pixel and Display Inorganic light emitting diodes for flat panel displays are disclosed in U.S. Patent No. 9,818,725, entitled “Large Format Micro-LED Display.” Such micro-LEDs are not readily combined with phosphor or quantum dots to emit white light, because the required layer thickness of phosphor or quantum dots needed to absorb sufficient light is large compared to the size of the micro-LED. For example, the thickness of the phosphor or quantum dot layer can be 20 to 100 microns, while the thickness of the micro-LED can be less than 20 microns.

[0009] In contrast to the light emitting layer of an OLED, an inorganic light emitting diode is a semiconductor light source that relies on a p-n junction, which emits light when a suitable voltage is applied across the light emitting diode. The color of light emitted from an iLED corresponds to the energy bandgap of the semiconductor. Thus, different semiconductor materials can emit different colors of light when excited with appropriately different voltages. Typical materials include InGaN (emitting blue light), AlGaP (emitting green light), and AlGaAs (emitting red light), among many others. Materials that emit blue light can emit light at a voltage range of 2.5 to 3.7 volts, materials that emit green light can emit light at a voltage range of 1.9 to 4 volts, and materials that emit red light can emit light at a voltage range of 1.6 to 2 volts, e.g., as taught in U.S. Patent No. 10,453,826, entitled “Large Format Micro-LED Display.” Voltage-Balanced Serial ILED Pixel and Display Figures 1-7 In addition, the efficiency of light emission by different materials can depend on the current density through the material.

[0010] To provide the different voltages and currents needed by different light-emitting diodes that emit different colors of light in a full-color pixel or white light illuminator that includes micro-LEDs, separate power supplies and controllers can provide power, ground, and control signals to each micro-LED. By providing each micro-LED with the appropriate voltage and current, the micro-LED effectively emits light. However, providing three (or more) different power, ground, and control signals to each color pixel or white light illuminator can require at least three times more power, wires, signals, and connections, thereby reducing the resolution of the display and increasing the cost. Alternatively, a single power supply can provide power to all three (or more) different iLEDs. In this case, any overvoltage drop across the other circuit elements, thereby increasing heat and reducing the power efficiency of the overall display system.

[0011] Accordingly, there is a need for an improved white light emitting micro-LED structure that improves power efficiency and reduces circuitry, wiring, and assembly costs. SUMMARY

[0012] According to some embodiments of the present disclosure, a white light emitting inorganic light-emitting diode (iLED) structure includes first iLEDs electrically connected in series and a second iLED electrically connected to one of the first iLEDs, each first iLED emitting light of a different color than any other first iLED when power is provided to the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs. The second iLED can be electrically connected in series or in parallel with one of the first iLEDs that emits light of the same color. In some embodiments, the iLED structure includes two or more second iLEDs, each second iLED electrically connected in series or in parallel with one of the first iLEDs, each second iLED emitting light of the same color as the one of the first iLEDs to which it is electrically connected in series or in parallel when power is provided to the first iLEDs.

[0013] According to some embodiments, the first iLEDs include red first iLEDs that emit red light and cyan first iLEDs that emit cyan light, blue first iLEDs that emit blue light and yellow first iLEDs that emit yellow light, or red first iLEDs that emit red light, green first iLEDs that emit green light, and blue first iLEDs that emit blue light. In some embodiments, the first iLEDs include red first iLEDs that emit red light and cyan first iLEDs that emit cyan light, and the second iLEDs include red second iLEDs that emit red light electrically connected in series with the first iLEDs. In some embodiments, the first iLEDs include yellow first iLEDs that emit yellow light and blue first iLEDs that emit blue light, and the second iLEDs include yellow second iLEDs that emit yellow light electrically connected in series with the first iLEDs.

[0014] In some embodiments, the first iLEDs include red first iLEDs that emit red light, green first iLEDs that emit green light, and blue first iLEDs that emit blue light, and the second iLEDs include red second iLEDs that emit red light electrically connected in series with the red first iLEDs. In some embodiments, the first iLEDs include red first iLEDs that emit red light, green first iLEDs that emit green light, and blue first iLEDs that emit blue light, and the second iLEDs include green second iLEDs that emit green light electrically connected in parallel with the green first iLEDs. In some embodiments, the first iLEDs include red first iLEDs that emit red light, green first iLEDs that emit green light, and blue first iLEDs that emit blue light, the second iLEDs include green second iLEDs electrically connected in parallel with the green first iLEDs and red second iLEDs electrically connected in series with the red first iLEDs, the green second iLEDs emitting green light when power is provided to the first iLEDs, and the red second iLEDs emitting red light when power is provided to the first iLEDs.

[0015] According to some embodiments of the disclosure, one of the second iLEDs and the second iLEDs electrically connected in series or in parallel in the first iLEDs is disposed on an integral and contiguous common homogeneous substrate in a common patterned semiconductor layer comprising a common semiconductor material, thereby forming a multi-LED structure. According to some embodiments, the iLED structure of the disclosure comprises a structural substrate, and the common homogeneous substrate of any individual first iLED, any individual second iLED, and any multi-LED structure is disposed on the structural substrate. According to some embodiments, an individual first iLED, an individual second iLED, or a second multi-LED structure comprising first iLEDs can be disposed on the integral and contiguous common homogeneous substrate of a first multi-LED structure.

[0016] According to some embodiments, at least some of the first LEDs comprise at least a portion of a tether, the second iLEDs comprise at least a portion of a tether, or both. Further, the multi-LED structure can comprise at least a portion of a tether, for example a portion of the common homogeneous substrate of the multi-LED structure.

[0017] According to embodiments of this disclosure, a color inorganic light-emitting diode (iLED) display includes a color pixel array. Each color pixel includes a color sub-pixel iLED and a white sub-pixel. When power is supplied to the color sub-pixel iLED, the color sub-pixel iLED emits colored light. The white sub-pixel includes a white-emitting iLED structure, which emits white light when power is supplied to the white sub-pixel. The white-emitting iLED structure may include one or more multi-LED structures. In some configurations, the color iLED display includes a display substrate, and the color pixels are disposed on the display substrate. A first iLED, a second iLED, one or more of the color sub-pixel iLEDs, or any multi-LED structure may include connecting pillars, broken or separated chains, or both. The color iLED display may include a black adhesive or black photoresist disposed on the display substrate, which adheres the first iLED, the second iLED, one or more of the color sub-pixel iLEDs, or one or more of any multi-LED structure to the display substrate. The connecting posts extend through black adhesive or black photoresist to the display substrate to form an electrical connection to the display substrate.

[0018] According to embodiments of this disclosure, a white-light-emitting inorganic light-emitting diode (iLED) lamp or illuminator includes a plurality of white-light-emitting inorganic light-emitting diode (iLED) structures. At least some of the plurality of white-light-emitting iLED structures can be electrically connected in parallel. At least some of the plurality of white-light-emitting iLED structures can be electrically connected in series.

[0019] The embodiments disclosed herein provide an improved white-emitting microLED structure that improves power efficiency and reduces circuit, wiring, and assembly costs. Attached Figure Description

[0020] The above and other objects, aspects, features, and advantages of this disclosure will become clearer and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:

[0021] Figure 8 This is an electrical schematic diagram based on an illustrative embodiment of this disclosure;

[0022] Figure 9 This is a graph illustrating the current density versus efficiency of red, green, and blue iLEDs for understanding embodiments of this disclosure;

[0023] Figure 10 This is a perspective view of a micro-transfer horizontal inorganic light-emitting diode according to an illustrative embodiment of the present disclosure;

[0024] Figures 11-12This is a perspective view of a micro-transfer horizontal multi-LED structure formed in a common semiconductor layer having a common material according to an illustrative embodiment of the present disclosure, the common semiconductor layer having an integral and adjacent common homogeneous substrate;

[0025] Figure 13 This is a perspective view of a white-emitting iLED structure including a multi-LED structure according to an illustrative embodiment of this disclosure;

[0026] Figure 14 This is a perspective view of micro-transfer RGBW pixels according to an illustrative embodiment of this disclosure;

[0027] Figure 15 This is a perspective view of a display according to an illustrative embodiment of the present disclosure;

[0028] Figure 16 A cross-section of an iLED having connecting posts adhered to a display substrate with black adhesive, according to an illustrative embodiment of this disclosure; and

[0029] Figures 1-7 This is a perspective view of a lamp according to an illustrative embodiment of this disclosure.

[0030] The features and advantages of this disclosure will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, in which the same reference numerals consistently identify corresponding elements. In the drawings, similar reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. The drawings are not drawn to scale because the dimensions of the various elements vary too much to be depicted to scale. Detailed Implementation

[0031] Embodiments of this disclosure provide electrically connected iLEDs in a white-light-emitting inorganic light-emitting diode (iLED) structure, featuring improved efficiency and simplified power and control circuitry, as well as increased density, fewer components, and fewer manufacturing steps. Such electrically connected iLEDs can be white-light subpixels in one or more pixels of a display, or white-light-emitting elements in lamps, indicators, or other illuminators. In some embodiments, the power supply provides any or more of a single current source, a single constant current source, and a single voltage source to the iLED in the pixel, indicator, or lamp. In some embodiments, the white-light-emitting inorganic light-emitting diode (iLED) structure of this disclosure provides improved color temperature and efficiency. As used herein, white light comprises a mixture of different colors of light and has a color that is closer to the desired white light color temperature standard than the light emitted by any emitter contributing white light, such as soft white (2700K-3000K), bright white / cool white (3500K-4100K), and daylight (5000K-6500K) or display monitor standard (e.g., 6500K).

[0032] According to some embodiments of this disclosure, and as Figures 1-3 As shown, the white-light-emitting inorganic light-emitting diode structure 99 (iLED structure 99) includes first iLEDs 10 connected in series. When power is supplied to the first iLEDs 10, each first iLED 10 emits light of a different color than any other first iLED 10 in the iLED structure 99. A second iLED 20 is electrically connected to one of the first iLEDs 10. When power is supplied to the first iLEDs 10, the second iLED 20 emits light of the same color as said one of the first iLEDs 10.

[0033] refer to Figures 6-7 and Figure 6 The first iLED 10 includes a red iLED 40R that emits red light, a green iLED 40G that emits green light, and a blue iLED 40B that emits blue light (collectively referred to as iLED 40 or microLED 40). The first iLED 10 are electrically connected in series and together emit white light (appearing as white light when observed by an observer) when power is supplied through the first electrode 91 and the second electrode 92 electrically connected to the ends of the series-connected first iLED 10. Figure 1 The iLED structure 99 also includes a first iLED 10 connected in series, emitting yellow light (yellow iLED 40Y) and cyan light (cyan iLED 40C). Through the electrically connected yellow iLED 40Y and cyan iLED 40C (or either yellow iLED 40Y or cyan iLED 40C), the correlated color temperature (CCT) of the iLED structure 99 can be improved by emitting more different colors of light. Reference Figure 3 , Figure 6 , Figure 7 and Figures 2-4 The green iLED 40G is the second iLED 20 and is electrically connected in parallel with the green iLED 40G, which is the first iLED 10. By providing a second iLED 20 connected in parallel with the first iLED 10 that emits light of the same color, the current density in the first iLED 10 and the second iLED 20 of the same color is reduced by half.

[0034] refer to Figures 2-4 The first iLED 10 includes a red iLED 40R that emits red light, a green iLED 40G that emits green light, and a blue iLED 40B that emits blue light. The first iLEDs 10 are electrically connected in series and emit white light when powered via a first electrode 91 and a second electrode 92 electrically connected to the ends of the series-connected first iLEDs 10. (Reference) Figure 3The red iLED 40R is the second iLED 20 and is electrically connected in series with the first iLED 10. By providing the second iLED 20 in series with the first iLED 10 that emits light of the same color, the voltage across the first iLED 10 and the second iLED 20 of the same color is doubled and I is reduced. 2 R represents power loss.

[0035] Figure 1 The implementation scheme shown will Figure 2 and Figure 7 The series and parallel electrical connections are combined into a single iLED structure 99. Figure 3 The implementation scheme shown will Figures 1-3 The iLED structure 99 is replicated into a single iLED structure 99 having twice the number of iLEDs 40 connected in series, thereby increasing the driving voltage of the iLED structure 99 and reducing I when distributing power to the iLED structure 99. 2 R represents power loss.

[0036] Figure 6 , Figure 7 and Figure 6 A first iLED 10 is shown in series connection of an iLED structure 99 including a red iLED 40R, a green iLED 40G, and a blue iLED 40B, according to some embodiments. Figure 4 The first iLED 10 also includes a yellow iLED 40Y and a cyan iLED 40C. In some implementations, such as Figure 5 and Figure 4 As shown, the first iLED 10 includes two iLEDs 40, which emit complementary colors of light to form white light. (Reference) Figure 5 The first iLED 10 includes a red iLED 40R, a cyan iLED 40C, and a second iLED 20. When power is supplied through the first electrode 91 and the second electrode 92, the red iLED and the cyan iLED emit complementary red and cyan light, respectively, while the second iLED emits red light. (Reference) Figure 8The first iLED 10 includes a blue iLED 40B, a yellow iLED 40Y, and a second iLED 20. When power is supplied through the first electrode 91 and the second electrode 92, the blue iLED and the yellow iLED emit complementary blue and yellow light, respectively, while the second iLED emits yellow light. Therefore, the first iLED 10 may include two or more iLEDs 40 connected in series, each emitting light of a different color when powered. Because the red iLED 40R and the yellow iLED 40Y are generally less efficient than the blue iLED 40B or the green iLED 40G, the second iLED 20 can be improved by emitting more red or yellow light and by increasing the driving voltage of the iLED structure 99 and reducing the IT in the iLED structure 99. 2 The color temperature of the white light emitted by the iLED structure 99 is improved by reducing power loss and power distribution loss of the iLED structure 99.

[0037] The iLED structure 99 of this disclosure provides improved light output efficiency. According to some embodiments of this disclosure, the red iLED 40R, green iLED 40G, and blue iLED 40B each have different light output efficiencies relative to the current density in the respective iLED 40. According to some embodiments, the red iLED 40R, green iLED 40G, and blue 40B may also have different preferred driving voltages, such as different forward voltages across the diodes. Figure 8 As shown, the blue LED 40B has a blue efficiency versus current density curve 71, the green LED 40G has a green efficiency versus current density curve 72, and the red LED 40R has a red efficiency versus current density curve 73; typically, each of these is different. The blue efficiency versus current density curve 71 has a maximum blue efficiency of 71M, the green efficiency versus current density curve 72 has a maximum green efficiency of 72M, and the red efficiency versus current density curve 73 has approximately a maximum red efficiency of 73M (assuming a given...). Figure 8 The finite dataset obtained and drawn in the process can be in a position greater than that in the past. Figure 1 (The larger current density shown).

[0038] Because the maximum green efficiency of the green iLED 40G (72MΩ) is roughly half that of the maximum blue efficiency of the blue iLED 40B (71MΩ), for a given current and iLED 40 size, for example... Figure 3 , Figure 6 , Figure 7 and Figure 6As shown, the second green iLED 40G (e.g., the second iLED 20) is electrically connected in parallel with the green iLED 40G of the first iLED 10 such that the current density through each individual green iLED 40G is half the current through the blue iLED 40B. Therefore, the green iLED 40G can operate approximately at its maximum green efficiency of 72MΩ, and the blue iLED 40B can simultaneously operate at approximately its maximum blue efficiency of 71MΩ with a suitably selected current, thereby improving the efficiency of the iLED structure 99. According to some embodiments of this disclosure, generally speaking, the iLED 40 of the first iLED 10, whose maximum efficiency is less than the maximum current density required for the iLED 40 of the first iLED 10 to operate at its maximum efficiency, can be electrically connected in parallel with the second iLED 20 emitting light of the same color to reduce the current density of the iLED 40 emitting said color light and increase the light emission efficiency in the iLED structure 99. For example, in an iLED structure 99 including a red first iLED 40R, a green first iLED 40G, and a blue first iLED 40B, three blue second iLEDs 40B connected in parallel with the blue first iLED 40B and seven green iLEDs 40G connected in parallel with the green first iLED 40G can all operate near their maximum efficiency.

[0039] Light-emitting systems including the iLED structure 99 of this disclosure can improve their electrical efficiency and reduce IE by employing a larger driving voltage. 2 R represents power loss. By increasing the number of iLEDs 40 connected in series in the iLED structure 99, such an increased voltage can be used to directly drive the iLED structure 99 without voltage conversion (e.g., DC to DC voltage conversion), such as... Figure 7 As shown. Figure 3 It shows examples of Figure 8 This implementation scheme features twice the driving voltage and therefore further reduced power distribution losses. Furthermore, because the red iLED 40R is... Figures 2-4 The least efficient iLED 40 shown, according to some embodiments of this disclosure, is supplemented with a red iLED 40R (or a yellow iLED 40Y, not shown in the figure) as a second iLED 20, for example as... Figure 7 and Figure 9As shown. Such additional iLEDs 40 can adjust the white point of the iLED structure 99. More generally, additional iLEDs 40 (e.g., red iLED 40R or yellow iLED 40Y) can be used as second iLEDs 20 to adjust the CCT and white point of the iLED structure 99 by providing additional light emission of the desired color. Thus, some embodiments of this disclosure provide an iLED structure 99 with improved color, color temperature, luminous efficiency, and power distribution.

[0040] The iLED 40 that can be used in embodiments of this disclosure is typically constructed by depositing and patterning an epitaxial layer on a substrate (e.g., an insulating substrate, such as sapphire). Such iLED 40 can be individually printable (e.g., microtransferable), as described, for example, in U.S. Patent Nos. 9,368,683, 10,224,231, 10,431,487, 10,395,966, and 10,600,671. Figure 9 A micro-transfer iLED 40 with iLED tether 25 is shown. Two electrical contacts are shown on iLED 40, but are not labeled. iLED 40 can emit light when power is supplied to the electrical contacts. Either or both of the first iLED 10 and the second iLED 20 can be micro-transferable or micro-transferable iLEDs, and either or both of the first iLED 10 and the second iLED 20 may include a broken or separated iLED tether 25, for example as a result of micro-transferring the first iLED 10 or the second iLED 20, such as... Figure 10 As shown.

[0041] However, according to some embodiments of this disclosure, by forming a plurality of iLEDs 40 in a common epitaxial layer on a monolithic and adjacent common homogeneous substrate 30 and patterning them in a common step, a plurality of iLEDs 40 emitting a common color light (e.g., a red iLED 40R as a first iLED 10 and a red iLED 40R as a second iLED 20) can be transferred or assembled into a single iLED 40, such as Figure 10As shown. Conversely, even if formed on a common wafer, the separate diced LED substrates are not monolithic and adjacent separate substrates for the separate LEDs, because the separate LEDs are no longer common once diced. Then, multiple common color iLEDs 40 on the common homogeneous substrate 30 are electrically connected together in series or parallel, for example, using photolithography and materials (e.g., metal wires), to form a single multi-LED structure 36 having a single monolithic and adjacent common homogeneous substrate 30, and are provided with one or more common substrate chains 35 for the multi-LED structure 36. (Since the iLEDs 40 in the multi-LED structure 36 are formed as a single unit using a single die post and are co-transferred on the common homogeneous substrate 30, an LED chain 25 is not provided for each individual iLED 40.) Each multi-LED structure 36 can be micro-transferred as a unit, for example, as Figure 11 As shown, the multi-LED structure 36 has a broken or separated common substrate chain 35. Such a multi-LED structure 36 can be constructed using photolithography methods and materials used in the field of light-emitting diodes, and provides a reduced number of micro-transfer steps (one for each multi-LED structure 36, rather than one for each iLED 40) and a reduced area (because the iLED 40 in the multi-LED structure 36 can be formed using a relatively high-resolution photolithography method rather than a relatively low-resolution micro-transfer method), making the iLED structure 99 require less physical space and can be assembled at a lower cost. Therefore, according to some embodiments of this disclosure, one or more second iLEDs 20 and first iLEDs 10 emitting light of a common color are disposed on an integrally adjacent common homogeneous substrate 30 in a commonly patterned semiconductor layer, for example comprising a common semiconductor material (e.g., comprising an alloy that can vary stoichiometrically). The patterned semiconductor layer may comprise multiple sublayers, and each sublayer may be doped or undoped separately and differently, for example, as a conductive layer or a light-emitting layer. The common color is the same color within the variability of the manufacturing process, and the monolithic substrate is a single adjacent substrate that has not been split, divided, or cut into spatially separated parts. The common homogeneous substrate 30 may include at least a portion of a chain, such as a common substrate chain 35, which may be a whole chain, for example, when attached to the source wafer, or a broken or separated chain after printing.

[0042] According to some embodiments of this disclosure, and as Figure 11As shown, the first iLED 10 and the second iLED 20 of the iLED structure 99 may be disposed on the structural substrate 50 (e.g., a non-homogeneous substrate). Individual iLEDs 40 (e.g., blue iLED 40B) may be disposed on the structural substrate 50, for example, by micro-transfer, and may include broken or separated iLED chains 25 (e.g., blue iLED chains 25B). In some embodiments, a multi-LED structure 36 may be disposed on the structural substrate 50, for example, by micro-transfer, and the multi-LED structure 36 itself may be micro-transferred from a source structure wafer and may include structural substrate chains 55. Figure 12 An iLED structure 99 including a structural substrate 50 is shown, wherein a red multi-LED structure 36R (including a red iLED 40R), a green multi-LED structure 36G (including a green iLED 40G), and a blue iLED 40B are disposed on the structural substrate 50.

[0043] In some implementations, such as Figure 12 As shown, the iLED 40 (e.g., blue iLED 40B) and the second multi-LED structure 36 can be disposed on a first common homogeneous substrate 30 of the multi-LED structure 36. Still referring to... Figure 13 The iLED structure 99 includes: a red multi-LED structure 36R (including a red iLED 40R disposed on a red common homogeneous substrate 30R, which is also a structural substrate 50); a green multi-LED structure 36G (including a green iLED 40G disposed on a green common homogeneous substrate 30G having a green common substrate chain 35G), wherein the green common homogeneous substrate 30G is disposed on the red common homogeneous substrate 30R; and a blue iLED 40B disposed on the red common homogeneous substrate 30R. The iLED structure 99 also includes a structural substrate chain 55, which is also a red common substrate chain 35R.

[0044] The iLED structure 99 disclosed herein can be used, for example, but not limited to, displays, lamps (illuminators), and indicators. For example, such as Figure 14 As shown, the iLED structure 99 can be the fourth white-emitting sub-pixel 64 in the color pixel 60 of the display 80 (e.g., Figure 13 (As shown). Reference Figure 14 The color pixel 60 includes a pixel substrate (e.g., a structural substrate 50), three color sub-pixels 62 (e.g., including a red iLED 40R, a green iLED 40G, and a blue iLED 40B) each emitting a different color of light, a white sub-pixel 64 (e.g., an iLED structure 99), and a pixel controller 52 that controls each color sub-pixel 62 and the white sub-pixel 64. Figure 15As shown, the display 80 may include an array of color pixels 60 arranged in an array on a display substrate 84 and electrically connected (e.g., via row and column lines, not shown) to a display controller 82. Therefore, according to some embodiments of this disclosure, the color inorganic light-emitting diode (iLED) display 80 includes an array of color pixels 60, each color pixel 60 including a color sub-pixel 62 iLED 40 and a white sub-pixel 64, wherein the color sub-pixel iLED 40 emits colored light when power is supplied to it, and the white sub-pixel includes a white-emitting iLED structure 99, which emits white light when power is supplied to the white sub-pixel 64. The display 80 may include a display substrate 84, and the color pixels 60 including the color sub-pixels 62 and the white sub-pixels 64 may be disposed on the display substrate 84 and controlled by the display controller 82.

[0045] The connecting post 26 is an electrical connection formed on the side of a printable (e.g., microtransferable) element (such as an iLED 40, a multi-LED structure 36, or an iLED structure 99), extending from the surface of the element, for example, perpendicularly from the surface. Such connecting posts 26 may be formed of a metal such as aluminum, titanium, tungsten, copper, silver, gold, or other conductive metals. According to some embodiments, any or more of the first iLEDs 10, one or more of the second iLEDs 20, one or more of the color sub-pixels 62 iLEDs 40, and any common homogeneous substrate 30 may include at least a portion of the connecting post 26 and ties (e.g., broken or separated ties) (e.g., iLED ties 25, common substrate ties 35, or structural substrate ties 55), for example, as... Figure 16 The image shows an iLED 40. For example, the iLED 40, common substrate 30, or structural substrate 50 can be attached to the source wafer via the entire iLED chain 25, common substrate chain 35, or structural substrate chain 55, respectively, and these chains can break or separate during the printing process. The display 80 may also include a black adhesive or black photoresist 86 disposed on the display substrate 84. When any of the iLED 40, common homogeneous substrate 30, or structural substrate 50 having connecting posts 26 is printed (e.g., micro-transfer printed) onto the display substrate 84, the connecting posts 26 can extend through the black adhesive or black photoresist 86 to reach electrical contact pads 85 on the display substrate 84, and the black adhesive or black photoresist 86 adheres one or more of the first iLED 10, one or more second iLEDs 20, or one or more multi-LED structures 36 to the display substrate 84.

[0046] According to some implementation plans, such as ​The illustrated white-light-emitting inorganic light-emitting diode (iLED) lamp 94 includes a plurality of white-light-emitting inorganic light-emitting diode (iLED) structures 99, which are disposed, for example, on a lamp substrate 96 and electrically connected in series or in parallel, or both, to provide white light illumination when powered by an electrical contact pad 85.

[0047] According to some embodiments of this disclosure, the first iLED 10 and the second iLED 20 are microLEDs 40 whose width and length are at least no greater than 500 micrometers (e.g., no greater than 200 micrometers, no greater than 100 micrometers, no greater than 50 micrometers, no greater than 25 micrometers, no greater than 15 micrometers, no greater than 12 micrometers, no greater than 8 micrometers, or no greater than 5 micrometers). The first iLED 10 and the second iLED 20 may have different sizes. The microLEDs 40 according to some embodiments of this disclosure offer advantages because they are small enough and can be spatially compacted such that, at the desired viewing distance, the different microLEDs 40 in the color pixel 60 and color subpixel 62 or iLED structure 99 cannot be easily distinguished by the human visual system, thereby improving the color mixing of the light emitted by the iLEDs 40 and providing improvements in resolution and spatial integration. In some implementations, a single common mask group can be used to construct all iLEDs 40, and all iLEDs 40 have the same size, thereby reducing the construction cost of lamps 94, indicators, or displays 80 using the iLED structure 99 of this disclosure.

[0048] According to some implementations, the iLED 40 includes compound semiconductors, such as GaN or GaAs or doped GaN or GaAs constructed using photolithography methods and materials.

[0049] Therefore, according to some embodiments of this disclosure, the display controller 82, pixel controller 52, or lamp controller (not shown) provides a common voltage and current to all the first iLEDs 10 and second iLEDs 20 in the iLED structure 99 to drive all the first iLEDs 10 and second iLEDs 20 relatively efficiently. Since the first iLEDs 10 and second iLEDs 20 can each be driven most efficiently with a single current density (although the current density may differ for each of the red iLED 40R, green iLED 40G, and blue iLED 40B), it may be advantageous to drive the iLEDs 40 with a time-modulation control scheme such as pulse width modulation (PWM) such that the voltage and current remain constant when driving each of the iLEDs 40. In some embodiments of this disclosure, the iLED structure 99 is driven at a higher voltage than any individual iLED 40, for example, to improve power distribution on the display substrate 84 or lamp substrate 96.

[0050] In some embodiments, the relative efficiency of the iLEDs 40 in the iLED structure 99 is controlled by controlling the relative area or volume, such as the luminous area or volume, of the red iLED 40R, green iLED 40G, or blue iLED 40B. In some embodiments of the iLED 40, the green iLED 40G operates most efficiently at a lower current density than the blue iLED 40B. A lower current density in a single iLED 40 at a given current can be achieved by increasing the relative size of the luminous area or volume of the single iLED 40. Therefore, according to some embodiments of this disclosure, a large green iLED 40G includes a larger luminous area or volume than a small blue iLED 40B; for example, the green iLED 40G is larger than the blue iLED 40B. Similarly, in some embodiments of the iLED 40, the red iLED 40R operates most efficiently at a higher current density than the blue iLED 40B. A higher current density in a single iLED 40 at a given current can be achieved by reducing the relative size of the luminous area or volume of the individual iLED 40. Therefore, according to some embodiments of this disclosure, a small red iLED 40R includes a smaller luminous area or volume than the blue iLED 40B or the green iLED 40G; for example, the red LED 40R is smaller than the blue iLED 40B or the green iLED 40G, or both. According to some embodiments of this disclosure, the ratio of the area or volume of one iLED 40 to the area or volume of another different iLED 40 is similar to, depends on, is approximately equal to, or substantially equal to the ratio of the maximum efficiency of one iLED 40 to the maximum efficiency of the other iLED 40. Therefore, the luminous area or volume of a pair of iLEDs 40s of different sizes can be negatively correlated with the maximum efficiency of the iLED 40 pair.

[0051] As used herein, two iLEDs 40 connected in series are two iLEDs 40 each having a first electrical terminal and a second electrical terminal connected in series, such that the first terminal of iLED 40 is electrically connected to the second terminal of the other iLED 40. The remaining two terminals are electrically connected to a common voltage signal or a common ground signal. Two iLEDs 40 connected in parallel have their first terminals connected together, and their second terminals are similarly connected together. The first and second terminals are electrically connected to a common voltage signal or a common ground signal and a control signal, respectively. Both iLEDs 40 are biased in the same positive direction. When one or more iLEDs 40 are simply a single iLED 40, a series (or parallel) connection of an iLED 40 means that the iLED 40 itself is simply electrically connected to a common voltage signal 54 or a common ground signal 56 and a control signal, respectively.

[0052] Each or every one of the iLEDs 40 may have a width of 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm), a length of 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm), or a height of 2 to 50 μm (e.g., 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm).

[0053] For example, methods for forming useful microtransferable structures are described in the paper “AMOLED Displays using Transfer-Printed Integrated Circuits” and U.S. Patent 8,889,485. For a discussion of microtransfer technology, see U.S. Patent Nos. 8,722,458, 7,622,367, and 8,506,867, the disclosures of which are incorporated herein by reference in their entirety. Microtransfer using composite microassembly structures and methods may also be used with this disclosure, for example, as described in U.S. Patent Application Serial No. 14 / 822,868, filed August 10, 2015, entitled “Compound Micro-Assembly Strategies and Devices,” the disclosure of which is incorporated herein by reference in its entirety. In some embodiments, the pixel is a composite microassembly device.

[0054] Microtransferable elements, such as iLED 40, multi-LED structure 36, or iLED structure 99, can be constructed using casting manufacturing processes used in the art. Material layers can be used, including materials such as metals, oxides, nitrides, and other materials used in the field of integrated circuits. Each element can be, contains, or includes a complete semiconductor integrated circuit and may include, for example, a light-emitting layer or structure. Elements can have different dimensions, for example, not exceeding 1000 square micrometers, 10,000 square micrometers, 100,000 square micrometers, or 1 square millimeter or larger, and can have variable aspect ratios, for example, at least 1:1, 2:1, 5:1, or 10:1. Elements can be rectangular or can have other shapes.

[0055] As those skilled in the art will understand, the terms "above" and "below" are relative terms and may be used interchangeably with reference to the different orientations of layers, elements, and substrates included in this disclosure. For example, in some embodiments, "first layer on second layer" means that the first layer is directly on and in contact with the second layer. In other embodiments, "first layer on second layer" includes the first layer and the second layer, with another layer in between.

[0056] Certain specific embodiments of the implementation have been described, and it will now become apparent to those skilled in the art that other specific embodiments can be used in conjunction with the concepts of this disclosure. Therefore, this disclosure should not be limited to certain specific embodiments, but should be limited only by the spirit and scope of the appended claims.

[0057] Unless there is technical incompatibility, the various embodiments described herein may be used in combination with one or more other embodiments.

[0058] Throughout this specification, where devices and systems are described as having, including, or containing specific components, or where processes and methods are described as having, including, or containing specific steps, it is anticipated that there will also be devices and systems that are substantially composed of or comprised of the described components, and processes and methods that are substantially composed of or comprised of the described processing steps, in accordance with the disclosed technology.

[0059] It should be understood that the order of steps or the sequence of actions is not important as long as operability remains. Furthermore, in some cases, two or more steps or actions may be performed simultaneously. This disclosure has been described in detail with specific reference to certain embodiments thereof, but it will be understood that variations and modifications may be made within the spirit and scope of the claimed invention.

[0060] Parts list

[0061] 10 First iLED

[0062] 20 Second iLED

[0063] 25 iLED Series

[0064] 25B Blue iLED Series

[0065] 26 Connecting Posts

[0066] 30 Common Homogeneous Substrates

[0067] 30G Green Common Homogeneous Substrate

[0068] 30R Red Common Homogeneous Substrate

[0069] 35 Common Substrate Chain

[0070] 35G Green Common Substrate System

[0071] 35R Red Common Substrate System

[0072] 36-LED structure

[0073] 36R Red Multi-LED Structure

[0074] 36G Green Multi-LED Structure

[0075] 40 Inorganic Light Emitting Diodes (iLEDs) / MicroLEDs

[0076] 40B Blue iLED

[0077] 40C Cyan iLED

[0078] 40G Green iLED

[0079] 40R Red iLED

[0080] 40Y Yellow iLED

[0081] 50 structural substrate

[0082] 52-pixel controller

[0083] 55 Structural Substrate Chain

[0084] 60 color pixels

[0085] 62 color subpixels

[0086] 64 white subpixels

[0087] 71 Blue efficiency versus current density / blue efficiency

[0088] 71M Blue Efficiency Maximum

[0089] 72 Green efficiency versus current density / green efficiency

[0090] 72M maximum green efficiency

[0091] 73 Red efficiency versus current density / red efficiency

[0092] 73M Red Efficiency Maximum

[0093] 80 monitors

[0094] 82 Display Controller

[0095] 84 Display substrate

[0096] 85 Contact Pad

[0097] 86 Black Adhesive / Black Photoresist

[0098] 91 First Electrode

[0099] 92 Second electrode

[0100] 94 lights

[0101] 96 lamp substrate

[0102] 99. Inorganic light-emitting diode structure / iLED structure that emits white light.

Claims

1. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other of the first iLEDs when power is provided to the first iLEDs; and a second iLED electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein the second iLED is directly electrically connected in series with the one of the first iLEDs, wherein the second iLED and the one of the first iLEDs are homogenous to and disposed on an integral and contiguous common homogenous substrate in a common patterned semiconductor layer comprising a common semiconductor material, wherein the common homogenous substrate comprises a broken or separated tether, and wherein the first iLEDs comprise red first iLEDs emitting red light, green first iLEDs emitting green light, and blue first iLEDs emitting blue light, and the second iLED comprises a red second iLED electrically connected in series with the red first iLEDs emitting red light.

2. The iLED structure of claim 1 comprising a structural substrate, and wherein the first iLEDs and the common homogenous substrate are disposed on the structural substrate.

3. The iLED structure of claim 1, wherein the first iLEDs are homogenous to and disposed on the common homogenous substrate.

4. The iLED structure of claim 1, wherein: (i) at least one of the first iLEDs comprises a broken or separated tether.

5. A color inorganic light emitting diode, iLED, display comprising an array of color pixels, each color pixel comprising a color sub-pixel iLED (62) that emits a color light when power is provided to the color sub-pixel iLED, and a white sub-pixel comprising a white light emitting iLED structure that emits white light when power is provided to the white sub-pixel, wherein, The white light emitting iLED structure comprises: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other of the first iLEDs when power is provided to the first iLEDs; and a second iLED directly electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs; wherein the second iLED and the one of the first iLEDs are homogenous to and disposed on an integral and contiguous common homogenous substrate in a common patterned semiconductor layer comprising a common semiconductor material, wherein the common homogenous substrate comprises a broken or separated tether.

6. The color iLED display of claim 5, comprising a display substrate, wherein the color pixels are disposed on the display substrate, and wherein (i) each of the first iLEDs comprises a connecting post and a broken or detached tether, (ii) the second iLED comprises a connecting post and a broken or detached tether, (iii) each of one or more of the color sub-pixel iLEDs comprises a connecting post and a broken or detached tether, or (iv) any combination of (i)-(iii), and the color iLED display comprises a black adhesive or black photoresist disposed on the display substrate, wherein the connecting post extends through the black adhesive or black photoresist to the display substrate, and the black adhesive or black photoresist adheres (i) one or more of the first iLEDs, (ii) the second iLED, (iii) one or more of the color sub-pixel iLEDs, or (iv) any combination of (i)-(iii) to the display substrate.

7. A white light emitting inorganic light emitting diode (iLED) lamp comprising a plurality of the white light emitting inorganic light emitting diode (iLED) structures of claim 1.

8. The iLED lamp of claim 7, wherein at least some of the plurality of white light emitting iLED structures are electrically connected in parallel.

9. The iLED lamp of claim 7, wherein at least some of the plurality of white light emitting iLED structures are electrically connected in series.

10. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other first iLED when power is provided to the first iLEDs; and a second iLED electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein the first iLEDs comprise red first iLEDs that emit red light and cyan first iLEDs that emit cyan light, and the second iLED comprises a red second iLED that emits red light, the red second iLED being electrically connected in series with the first iLEDs, and wherein the second iLED and the one of the first iLEDs are homogeneous to and disposed on a unitary and contiguous common homogeneous substrate, the unitary and contiguous common homogeneous substrate being in a common patterned semiconductor layer comprising a common semiconductor material, wherein the common homogeneous substrate comprises a broken or detached tether.

11. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other first iLED when power is provided to the first iLEDs; and a second iLED electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein the first iLEDs comprise red first iLEDs that emit red light and cyan first iLEDs that emit cyan light, and the second iLED comprises a red second iLED that emits red light, the red second iLED being electrically connected in series with the first iLEDs, and wherein the second iLED and the one of the first iLEDs are homogeneous to and disposed on a unitary and contiguous common homogeneous substrate, the unitary and contiguous common homogeneous substrate being in a common patterned semiconductor layer comprising a common semiconductor material, wherein the common homogeneous substrate comprises a broken or detached tether. a second iLED electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein the first iLEDs include yellow first iLEDs that emit yellow light and blue first iLEDs that emit blue light, and the second iLEDs include yellow second iLEDs that emit yellow light electrically connected in series with the first iLEDs, and wherein the second iLEDs and the one of the first iLEDs are homogenous to and disposed on a unitary and contiguous common homogenous substrate that is in a common patterned semiconductor layer that includes a common semiconductor material, wherein the common homogenous substrate includes a broken or separated tether.

12. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other of the first iLEDs when power is provided to the first iLEDs, wherein the first iLEDs include red first iLEDs that emit red light, green first iLEDs that emit green light, and blue first iLEDs that emit blue light; and a green second iLED electrically connected in parallel with the green first iLEDs; and a red second iLED electrically connected in series with the red first iLEDs, wherein the second iLEDs and one of the first iLEDs are homogenous to and disposed on a unitary and contiguous common homogenous substrate that is in a common patterned semiconductor layer that includes a common semiconductor material, wherein the common homogenous substrate includes a broken or separated tether.

13. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other of the first iLEDs when power is provided to the first iLEDs; and two or more second iLEDs electrically connected to one of the first iLEDs, each of the two or more second iLEDs emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein at least one of the two or more second iLEDs is electrically connected in series with the one of the first iLEDs, and the at least one second iLED and the one of the first iLEDs are homogenous to and disposed on a unitary and contiguous common homogenous substrate that is in a common patterned semiconductor layer that includes a common semiconductor material, wherein the common homogenous substrate includes a broken or separated tether, and wherein the two or more second iLEDs are homogenous to and disposed on a unitary and contiguous common homogenous substrate that is in a common patterned semiconductor layer that includes a common semiconductor material, wherein the common homogenous substrate includes a broken or separated tether. each of the two or more second iLEDs is electrically connected in series or parallel with one of the first iLEDs.

14. A white light emitting inorganic light emitting diode (iLED) structure comprising: first iLEDs electrically connected in series, each of the first iLEDs emitting light of a different color than any other of the first iLEDs when power is provided to the first iLEDs; and a second iLED electrically connected to one of the first iLEDs, the second iLED emitting light of the same color as the one of the first iLEDs when power is provided to the first iLEDs, wherein the second iLED is electrically connected in series with the one of the first iLEDs, wherein the second iLED and the one of the first iLEDs are of a common homogenous substrate that is integral and contiguous, the common homogenous substrate being in a common patterned semiconductor layer comprising a common semiconductor material, wherein the common homogenous substrate comprises a broken or separated tether, and wherein the first iLEDs comprise red first iLEDs emitting red light, green first iLEDs emitting green light, and blue first iLEDs emitting blue light, and the second iLEDs comprise green second iLEDs electrically connected in parallel with the green first iLEDs emitting green light.

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