TWI898911B - Light-emitting element - Google Patents

Abstract

A light-emitting element includes a light source and an encapsulation layer covering the light source. An energy power distribution curve of the light-emitting element has a concave portion located between 1.4 eV and 1.6 eV.

Description

Light-emitting element

The disclosed embodiments relate to a light-emitting device, and more particularly to a light-emitting device having an energy power distribution curve including a concave portion.

Existing monitoring devices, such as driver monitoring systems (DMS) and facial recognition systems, typically incorporate a light source (e.g., a light-emitting diode or laser diode) whose primary emission peak falls within the invisible wavelength range. However, the emitted light still contains some perceptible visible light components, impacting the user experience.

A light-emitting element includes a light source and a packaging layer covering the light source. The energy power distribution curve of the light-emitting element has a concave portion, and the concave portion is between 1.4 eV and 1.6 eV.

The present disclosure provides a light-emitting element having an energy power distribution curve with a concave portion between 1.4 eV and 1.6 eV. This improves the perception of light emitted by the light-emitting element by the human eye without reducing the overall energy power of the light-emitting element, thereby optimizing the user experience.

The following describes some implementation methods of the light-emitting elements disclosed herein, so as to adjust the energy power distribution curve of the light-emitting element to have a concave portion between 1.4 eV and 1.6 eV. For the sake of simplicity, only one light-emitting element 10 is described in the following embodiments and figures, but in the actual process, multiple light-emitting elements 10 can be formed simultaneously. It should be understood that some elements may be omitted in the figures to highlight the features of the present disclosure. It should be noted that the same or similar processes or elements between the embodiments will use the same element symbols, and their details will not be repeated. In addition, the features of the various embodiments can be mixed and matched as needed as long as they do not violate the spirit of the present disclosure or conflict with each other.

Figures 1 and 2 are cross-sectional views of a light-emitting element 10 and its light source 120, respectively, according to some embodiments of the present disclosure. As shown in Figure 1, light-emitting element 10 includes light source 120. In some embodiments, light source 120 may be a light-emitting diode (LED) that emits infrared light, for example, in the wavelength range of 750 nanometers (nm) to 1000 nanometers (nm). The LED may be a sub-millimeter light-emitting diode (mini LED) or a micro LED, but the present disclosure is not limited thereto.

As shown in FIG. 2 , in some embodiments, light source 120 includes a light-emitting structure 1202 and a first electrical terminal 1204 and a second electrical terminal 1206 disposed on opposite sides of light-emitting structure 1202, but the present disclosure is not limited thereto. Depending on design requirements, first electrical terminal 1204 and second electrical terminal 1206 may also be disposed on the same side of light-emitting structure 1202. In this embodiment, first electrical terminal 1204 is disposed below light-emitting structure 1202, while second electrical terminal 1206 is disposed above light-emitting structure 1202.

In some embodiments, the light-emitting structure 1202 may include a first-type semiconductor layer, an active layer, and a second-type semiconductor layer (not shown) stacked in sequence. The first-type semiconductor layer, the active layer, and the second-type semiconductor layer may include III-V compound materials, such as aluminum (Al), gallium (Ga), arsenic (As), phosphorus (P), indium (In), or nitrogen (N). Specifically, in some embodiments, the III-V compound material may be a binary compound semiconductor (e.g., GaAs, GaP, GaN, or InP), a ternary compound semiconductor (e.g., InGaAs, AlGaAs, GaInP, AlInP, InGaN, or AlGaN), or a quaternary compound semiconductor (e.g., AlGaInAs, AlGaInP, AlInGaN, InGaAsP, InGaAsN, or AlGaAsP). The first-type semiconductor layer and the second-type semiconductor layer have different conductive properties. For example, the first-type semiconductor layer can be a P-type semiconductor layer, the second-type semiconductor layer can be an N-type semiconductor layer, and the active layer can be a quantum well structure or a multi-quantum well (MQW) structure. It is worth noting that in other embodiments, the first-type semiconductor layer can be an N-type semiconductor layer, and the second-type semiconductor layer can be a P-type semiconductor layer. The light-emitting structure 1202 can be formed using metal organic chemical-vapor deposition (MOCVD), liquid phase epitaxy (LPE), or molecular beam epitaxy (MBE), but the present disclosure is not limited thereto.

In some embodiments, the first electrical terminal 1204 and the second electrical terminal 1206 can serve as the positive and negative electrodes of the light-emitting structure 1202. The materials of the first electrical terminal 1204 and the second electrical terminal 1206 may include metals or conductive compounds. Metals include, for example, gold (Au), nickel (Ni), platinum (Pt), palladium (Pd), iridium (Ir), titanium (Ti), chromium (Cr), tungsten (W), aluminum (Al), copper (Cu), beryllium (Be), germanium (Ge), zinc (Zn), tin (Sn), alloys thereof, or combinations thereof. Conductive compounds include, for example, titanium nitride (TiN), indium tin oxide (ITO), indium zinc oxide (IZO), or zinc oxide (ZnO), but the present disclosure is not limited thereto. The first electrical terminal 1204 and the second electrical terminal 1206 can be formed by evaporation, sputtering, plating, etc.

Returning to FIG. 1 , in some embodiments, the light-emitting device 10 may include a carrier 100, with the light source 120 disposed on the carrier 100. The carrier 100 may be a substrate having conductive traces, such as a sapphire substrate, a silicon substrate, a glass substrate, a printed circuit board (PCB), a metal substrate, a ceramic substrate, a flexible substrate, the like, or a combination thereof, but the present disclosure is not limited thereto.

In some embodiments, the light-emitting device 10 includes a first lead frame 110a and a second lead frame 110b disposed on a carrier 100. In other words, the carrier 100 supports the first lead frame 110a, the second lead frame 110b, and the light source 120. The first lead frame 110a and the second lead frame 110b may be separate from each other, and the light source 120 may be disposed on the first lead frame 110a. In other embodiments, the light source 120 may be disposed on both the separate first lead frame 110a and the second lead frame 110b, or disposed elsewhere than the first lead frame 110a and the second lead frame 110b (e.g., directly on the carrier 100 or on a heat sink (not shown)). The first lead frame 110a is electrically connected to a first electrical terminal 1204 (as shown in FIG. 2 ) of the light source 120, while the second lead frame 110b is electrically connected to a second electrical terminal 1206 (as shown in FIG. 2 ) of the light source 120 via a wire 130. Thus, current injected from the first electrical terminal 1204 or the second electrical terminal 1206 can cause electrons and holes to recombine in the light-emitting structure 1202, thereby emitting light. In other embodiments, such as when the light source 120 is located on both the first lead frame 110a and the second lead frame 110b, the light-emitting device 10 may not include the wire 130. In still other embodiments, such as when the light source 120 is located outside the first lead frame 110a and the second lead frame 110b on the carrier 100, the light-emitting device 10 may include a plurality of wires 130.

In some embodiments, the first lead frame 110a and the second lead frame 110b may be made of a metal, such as copper, aluminum, silver, gold, or an iron-nickel alloy. The first lead frame 110a and the second lead frame 110b may be formed on the carrier 100 by stamping, electroplating, or deposition. In some embodiments, the wire 130 may be made of a conductive material, such as gold, copper, or aluminum. The wire 130 may be formed by a wire bonding process or a deposition process.

Still referring to FIG. 1 , the light-emitting device 10 includes a packaging layer 140 covering the light source 120, the first lead frame 110a, the wires 130, the second lead frame 110b, and the carrier 100. In some embodiments, the packaging layer 140 serves to isolate the light-emitting device 10 from the outside world, preventing moisture from infiltrating and reducing the actual operating life of the light-emitting device 10. Furthermore, in this embodiment, the packaging layer 140 includes an absorber material in addition to the packaging material. Specifically, the absorber material absorbs photons with energies between 1.4 eV and 1.6 eV, enabling the light-emitting device 10 to exhibit a specific energy power distribution curve 202 (shown in FIG. 3 ).

In some embodiments, the encapsulation material may include epoxy, silicone, polymethyl methacrylate (PMMA), polycarbonate (PC), acrylic, or other transparent, highly permeable encapsulant. The absorber material may include phthalocyanine, an azo compound, a squaraine, diimonium, phthalein, naphthol, copper carbonate, and/or combinations thereof, but the present disclosure is not limited thereto. Any material capable of absorbing photons with energies between 1.4 eV and 1.6 eV may be used. The absorber material may comprise 5 to 30% by volume of the encapsulation material. When the absorber material content is less than 5% by volume, insufficient absorption efficiency may result, failing to effectively reduce the proportion of photons with energies between 1.4 eV and 1.6 eV. Furthermore, this may lead to uneven light absorption distribution, impacting product performance consistency. When the absorber material content exceeds 30% by volume, the heat dissipation performance of the package layer 140 may be reduced, resulting in poor thermal management and impacting the overall stability and durability of the device.

FIG3 illustrates an energy power distribution curve of the light-emitting device 10 according to some embodiments of the present disclosure. In some embodiments, the main peak of the energy power distribution curve 202 is located between 1.2 eV and 1.4 eV, and a concave portion 2022 is formed between 1.4 eV and 1.6 eV, with the concave portion 2022 being concave toward the intersection of the coordinate axes. In other words, the energy power distribution curve 202 includes two slope inflection points (e.g., slope inflection points A and B) between 1.4 eV and 1.6 eV. Specifically, the energy power distribution curve 202 decreases from 1.4 eV to 1.6 eV at a first slope at slope inflection point A and decreases at a second slope at slope inflection point B, with the first slope being greater than the second slope. In some embodiments, the power value at slope inflection point A is at least 10 times greater than the power value at slope inflection point B. It should be noted that the outline of concave portion 2022 and the locations of slope inflection points A and B in FIG. 3 illustrate only one embodiment of the present disclosure and should not be considered limiting of its scope. In some embodiments, the ratio of the total power between 1.4 eV and 1.6 eV to the total power between 1.18 eV and 2.48 eV (red glow power ratio) of the energy power distribution curve 202 is less than 2% (e.g., 1%, 0.5%, or 0.1%). When the energy power distribution curve 202 has a concave portion 2022 between 1.4 eV and 1.6 eV or the above ratio is less than 2%, the proportion of this photon energy range can be relatively reduced. This can improve the perception of the light emitted by the light-emitting element 10 by the human eye without reducing the overall energy power of the light-emitting element 10, thereby optimizing the user experience.

In some embodiments, such as the light-emitting device 10, the energy power distribution curve 202 of the light-emitting device 10 can be adjusted to have a concave portion 2022 between 1.4 eV and 1.6 eV by using an absorbing material within the encapsulation layer 140. In some embodiments, the primary energy (i.e., the main peak of the energy power distribution curve) and distribution of the luminescence spectrum can be controlled by adjusting the material of the active layer in the light-emitting structure 1202, such that the main peak of the energy power distribution curve 202 is located between 1.2 eV and 1.4 eV (e.g., 1.32±0.03 eV), thereby relatively reducing the proportion of the photon energy range (e.g., 1.4 eV to 1.6 eV). For example, in an embodiment where the material of the active layer is InGaAs, the composition of InGaAs can be adjusted to In _0.3 Ga _0.7 As, and the energy is about 1.322 eV.

FIG4 and FIG5 are cross-sectional views of a light-emitting element 20 and its light source 122, respectively, according to other embodiments of the present disclosure. The light-emitting element 20 in FIG4 is similar to the light-emitting element 10 in FIG1 , except that the packaging layer 140 is replaced by the packaging layer 142, and the light source 120 is replaced by the light source 122.

Encapsulation layer 142 is similar to encapsulation layer 140 in FIG. 1 , except that encapsulation layer 142 does not include an absorbing material. Light source 122 is similar to light source 120 in FIG. 1 , except that light source 122 includes a quantum dot structure 1208. As shown in FIG. 5 , in some embodiments, quantum dot structure 1208 and second electrical terminal 1206 are disposed on the same side of light-emitting structure 1202. Quantum dot structure 1208 can absorb photons with energy greater than 1.32 eV (e.g., greater than 1.4 eV) and, upon excitation, radiate photons with energy between 1.2 eV and 1.4 eV (e.g., approximately 1.32 eV), thereby enabling light-emitting element 20 to have an energy power distribution curve 202. Quantum dots (QDs) described throughout this specification are semiconductor particles composed of Group II-VI or Group III-V elements. They typically range in size from a few nanometers to tens of nanometers and contain approximately 1×10 ³ to 1×10 ⁶ atoms.

In some embodiments, the material of the quantum dot structure 1208 may include indium arsenide (InAs), indium phosphide (InP), cadmium telluride (CdTe) or other suitable materials. The quantum dot structure 1208 may be formed on the light-emitting structure 1202 by epitaxial growth, but the present disclosure is not limited thereto, and other suitable formation methods are also applicable to the present disclosure. For other details about the light source 122, please refer to the light source 120 described in Figure 1, so they will not be repeated here. In some embodiments, a protective structure 1210 may be optionally provided on the quantum dot structure 1208 to prevent the quantum dot structure 1208 from being damaged by contact with moisture. The material of the protective structure 1210 may include zinc sulfide (ZnS) or zinc oxide (ZnO). In an embodiment where the quantum dot structure 1208 is indium arsenide (InAs), the protection structure 1210 may be zinc sulfide (ZnS).

In some embodiments, the quantum dot structure 1208 can be configured to position the primary peak of the energy power distribution curve 202 between 1.2 eV and 1.4 eV, thereby reducing the proportion of photon energies between 1.4 eV and 1.6 eV. This improves the perceptibility of light emitted by the light-emitting element 20 to the human eye without reducing the overall energy output of the light-emitting element 20, thereby optimizing the user experience. In other embodiments, the primary energy (i.e., the primary peak of the energy power distribution curve) and distribution of the luminescence spectrum can be adjusted by controlling the Stranski-Krastanov (SK) strain of the light-emitting structure 1202.

FIG6 and FIG7 are cross-sectional views of a light emitting device 30 and its light source 124 according to some other embodiments of the present disclosure. The light emitting device 30 in FIG7 is similar to the light emitting device 20 in FIG4 , except that the light source 122 is replaced by the light source 124.

Light source 124 differs from light source 122 in that light source 124 includes a distributed Bragg reflector (DBR) structure 1212 disposed on a side of the light-emitting structure 1202 that is distal from carrier 100. As shown in FIG. 7 , in some embodiments, Bragg reflector structure 1212 and second electrical terminal 1206 are disposed on the same side of the light-emitting structure 1202. In other embodiments, such as when first electrical terminal 1204 and second electrical terminal 1206 are located on the same side of the light-emitting structure 1202, Bragg reflector structure 1212 and second electrical terminal 1206 are disposed on opposite sides of the light-emitting structure 1202.

In some embodiments, the Bragg reflection structure 1212 can reflect photons with energy greater than 1.32 eV (eg, photon energy greater than 1.4 eV) to relatively reduce the proportion of photon energy in the range of 1.4 eV to 1.6 eV, so that the light-emitting element 30 can have an energy power distribution curve 202 .

In some embodiments, the Bragg reflection structure 1212 is formed by alternating stacks of two or more dielectric materials with different refractive indices, such as silicon nitride ( _SiNx ), titanium dioxide ( _TiO2 ), tantalum _pentoxide ( _Ta2O5 ), helium dioxide ( _HfO2 ), silicon dioxide ( _SiO2 ), zirconium dioxide ( _ZrO2 ), and _aluminum oxide ( _Al2O3 ). In some embodiments, the Bragg reflector structure 1212 is formed by alternating stacks of two or more III-V semiconductor materials with different refractive indices. Examples of the III-V semiconductor materials include aluminum arsenide (AlAs), aluminum gallium arsenide (AlGaAs), gallium phosphide (GaP), aluminum indium phosphide (AlInP), and aluminum indium gallium phosphide (AlInGaP). The Bragg reflector structure 1212 can be formed using metal organic chemical-vapor deposition (MOCVD), liquid phase epitaxy (LPE), or molecular beam epitaxy (MBE), but the present disclosure is not limited thereto. For further details regarding the light source 124, please refer to the light source 120 described in FIG. 1 and are not further described here.

In summary, the present disclosure provides a light-emitting element having an energy power distribution curve with a concave portion between 1.4 eV and 1.6 eV. This improves the perception of the invisible light of the light-emitting element by the human eye without reducing the overall energy power of the light-emitting element, thereby optimizing the user experience. For example, an absorbing material that can absorb photons with energies between 1.4 eV and 1.6 eV can be added to the packaging layer. For another example, a quantum dot structure can be provided in the light source to relatively reduce the ratio of photon energies between 1.4 eV and 1.6 eV. For another example, a Bragg reflection structure can be provided in the light source to relatively reduce the ratio of photon energies between 1.4 eV and 1.6 eV. The aforementioned examples can also be used in combination with each other.

The above overview of several embodiments is provided to facilitate understanding of the present invention by those skilled in the art. Those skilled in the art will appreciate that they can design or modify other processes and structures based on the present embodiments to achieve the same objectives and/or advantages as the embodiments described herein. Those skilled in the art will also appreciate that such equivalent processes and structures do not depart from the spirit and scope of the present invention, and that various modifications, substitutions, and replacements can be made without departing from the spirit and scope of the present invention.

10: Light-emitting element 100: Carrier 110a: First lead frame 110b: Second lead frame 120: Light source 1202: Light-emitting structure 1204: First electrical terminal 1206: Second electrical terminal 1208: Quantum dot structure 1210: Protective structure 1212: Bragg reflector structure 122: Light source 124: Light source 130: Wires 140: Encapsulation layer 142: Encapsulation layer 20: Light-emitting element 202: Energy power distribution curve 2022: Concave portion 30: Light-emitting element A: Slope inflection point B: Slope inflection point

The following details various aspects of the present disclosure, accompanied by the accompanying figures. It should be noted that, in accordance with standard industry practice, various components are not drawn to scale and are provided for illustrative purposes only. In fact, the dimensions of components may be arbitrarily enlarged or reduced to clearly illustrate the components of the disclosed embodiments. It should also be noted that the accompanying figures illustrate only exemplary embodiments of the present disclosure and should not be considered limiting of its scope; the present disclosure is equally applicable to other embodiments. Figures 1 and 2 are cross-sectional views of a light-emitting element and its light source, respectively, according to some embodiments of the present disclosure. Figure 3 is a graph illustrating the energy power distribution curve of a light-emitting element, according to some embodiments of the present disclosure. Figures 4 and 5 are cross-sectional views of a light-emitting element and its light source, respectively, according to other embodiments of the present disclosure. Figures 6 and 7 respectively illustrate cross-sectional views of a light-emitting element and its light source according to further embodiments of the present disclosure.

202: Energy Power Distribution Curve

2022: Concave

A: Slope turning point

B: Slope turning point

Claims (10)

A light-emitting element comprises: a light source; and a packaging layer covering the light source, wherein an energy power distribution curve of the light-emitting element has a concave portion, wherein the concave portion is between 1.4 eV and 1.6 eV, and wherein the ratio of the total power of the energy power distribution curve between 1.4 eV and 1.6 eV to the total power between 1.18 eV and 2.48 eV is less than 2%. The light-emitting element of claim 1, wherein the main peak of the energy power distribution curve is located between 1.2 eV and 1.4 eV. The light-emitting element of claim 1, wherein the energy power distribution curve includes two slope inflection points, the two slope inflection points include a first slope inflection point and a second slope inflection point, wherein the power value of the first slope inflection point is at least 10 times the power value of the second slope inflection point. The light-emitting element of claim 1, wherein the recess is recessed toward the coordinate intersection. The light-emitting element of claim 1, wherein the energy power distribution curve comprises two slope inflection points, and the two slope inflection points are located between 1.4 eV and 1.6 eV. The light-emitting device of claim 1, wherein the encapsulation layer comprises an absorption material, and the absorption material can absorb photons with photon energies between 1.4 eV and 1.6 eV. The light-emitting element of claim 6, wherein the absorption material includes phthalocyanine, azo compound, squarenine, diimonium, phthalein, naphthol, and/or copper carbonate. The light-emitting element of claim 1, wherein the light source includes a quantum dot structure that can absorb photons with energy greater than 1.32 eV and radiate photons with energy of approximately 1.32 eV after being excited. The light emitting device of claim 1, wherein the light source comprises a distributed Bragg reflector (DBR) structure, wherein the Bragg reflector structure can reflect photons with a photon energy greater than 1.32 eV. The light-emitting element of claim 1 further includes: a first lead frame electrically connected to a first electrical terminal of the light source; a second lead frame electrically connected to a second electrical terminal of the light source; and a carrier board supporting the first lead frame, the second lead frame, and the light source, wherein the packaging layer covers the light source, the first lead frame, the second lead frame, and the carrier board.