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  • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
  • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/42—Wire connectors; Manufacturing methods related thereto
  • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
  • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
  • H01L2224/4805—Shape
  • H01L2224/4809—Loop shape
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• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
  • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
  • H01L2224/42—Wire connectors; Manufacturing methods related thereto
  • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
  • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
  • H01L2224/481—Disposition
  • H01L2224/48151—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
  • H01L2224/48221—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
  • H01L2224/48245—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic
  • H01L2224/48247—Connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being metallic connecting the wire to a bond pad of the item
• • H—ELECTRICITY
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  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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  • H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
  • H01L33/50—Wavelength conversion elements
  • H01L33/501—Wavelength conversion elements characterised by the materials, e.g. binder
  • H01L33/502—Wavelength conversion materials

Definitions

• the present invention relates to light sources that are suitable for the use in outdoor lighting and only slightly disrupts the circadian rhythm of humans; more specifically the invention discloses light-emitting diodes that are composed of semiconductor short wavelength emitters that emit blue light due to electroluminescence and of inorganic phosphors that generate the orange components of spectral power distribution.
• CAF - circadian action factor the ratio of non-visual circadian efficacy to the luminous efficacy of radiation
• Phosphor - a certain material that converts light with a shorter wavelength to light with a longer wavelength
• Firelight - light that has a low correlated colour temperature ( ⁇ 2500 K) with the chromaticity that is similar to that of a black body radiation.
• High and low pressure sodium vapour lamps are distinguished by low CCT and small circadian action. However due to the scarce and structured spectrum they are characterized by extremely low colour rendering.
• a mercury vapour lamp is presented. The radiation of this lamp is characterized by a high radiation flux in the blue region and strongly affects the circadian rhythm of humans. Also under conditions of low luminance, the visual discomfort can appear due to the high CCT [A. A. ruithof, Tabular luminescence lamps for general illumination, Philips Tech. Rev. 6, p. 65-73 (1941)].
• the SPD of the optimal photobiologically friendly LED consists of two spectral components, whereas in the patent the LED with SPD consisting of three spectral components is described;
• the USA patent US 6,501, 102 discloses a trichromatic pcLED that contains a semiconductor chip emitting light with a wavelength shorter than 460 nm that is partially converted to a secondary and tertiary radiation in phosphors where at least one of those is composed of at least one of the following: yttrium aluminium oxide compound, strontium gallium sulphide, yttrium aluminium lanthanum oxide compound, yttrium aluminium gallium oxide compound, and strontium sulphide nitridosilicate. This blend of three colours is perceived by humans as white light. However, this kind of LED is not optimal for photobiologically friendly street lighting for the following reasons:
• the SPD of the optimal photobiologically friendly LED consists of two spectral components, whereas in the patent the LED with SPD consisting of three spectral components is described;
• the USA patent US 6,294,800 discloses a phosphor with the chemical composition of Ca8Mg(Si0 4 ) 4 Cl 2 :Eu 2+ ,Mn 2+ and a trichromatic pcLED that contains a semiconductor chip, which emits light in the 330 - 420 nm wavelength region, the mentioned Ca 8 Mg(Si0 4 ) 4 CI 2 :Eu 2+ ,Mn 2+ phosphor, in which a part of the primary radiation is converted to green light, Y 2 0 3 :Eu 3+ ,Bi 3+ phosphor, in which a part of the primary radiation is converted to red light, and BaMg 2 Al i 6 0 27 :Eu or (Sr,Ba,Ca) 5 (PO " 4)3Cl:Eu phosphor, in which a part of the primary radiation is converted to blue light.
• the chemical compositions of the phosphors used in the LED are not chosen such that their SPD would be optimal for outdoor lighting with the lowest circadian action factor.
• the USA patent 6,084,250 discloses a trichromatic pcLED that contains a GaN LED emitting radiation in the ultraviolet region with the emission peak between 300 and 370 nm, and blue BaMgAl ioOi 7 :Eu 2+ phosphor, in which the primary radiation is converted to radiation that peaks in the 430-490 nm region, green ZnS:Cu phosphor, in which the primary radiation is converted to radiation that peaks in the 520-570 nm region, and red Y 2 0 2 S phosphor, in which the primary radiation is converted to radiation, which peaks in the 590-630 nm region.
• This blend of three colours is perceived by humans as white light.
• this kind of LED is not optimal for photobiologically friendly street lighting for the following reasons:
• the SPD of the optimal photobiologically friendly LED consists of two spectral components, whereas in the patent the LED with SPD consisting of three spectral components is described;
• the US patent US 5,851 ,063 discloses an entirely electroluminescent array of different-colour LEDs, which can be used for obtaining a desired SPD of the light source.
• arrays require complex topology, which is needed for the layout of different groups of LEDs.
• direct-emission electroluminescent LEDs of different colours are driven by different currents, which requires a higher number of control channels and more complex electronic circuits than in the case of pcLEDs when the electroluminescent chip in all LEDs is the same.
• the LED described in this patent is composed of a semiconductor light emitting component and a phosphor.
• the semiconductor chip emits excitation light in the 400-530 nm wavelength region and the phosphor photoluminescence is chosen such that its peak wavelength would be longer than that of the excitation light.
• the following drawbacks are not avoided:
• the SPD of the LED is not optimized in such a way that the circadian action factor of radiated light is minimized, i.e., that during the evening or night the negative impact for the human organism would be as small as possible;
• phosphor converted firelight sources optimized for mesopic vision when the average luminance of the environment is between 0.01 and 10 cd/m 2 ) that are characterized by a several times smaller circadian action than that of common daylight LEDs [A. Zukauskas, R. Vaicekauskas, P. Vitta, Optimization of solid-state lamps for photobiologically friendly mesopic lighting, Appl. Optics 51(35), p. 8423-8432 (2012)] could be used.
• the present invention discloses a low CCT (firelight) LED, which has a spectral power distribution composed of a blue and an orange components. These components have such peak wavelengths and ratios of radiation fluxes that the ratio of the excitation of non-visual photoreceptors in the eye retina that are controlling the circadian rhythm and the excitation of visual photoreceptors causing the visual perception would be the lowest. In this way the minimal disruption of the human circadian rhythm is obtained.
• CCT firelight
• the ratio of radiant fluxes of the spectral components are set by adjusting the size and the concentration of phosphor particles, the thickness of the wavelength converter, the refraction index of the material of the wavelength converter, the distance between the wavelength converter and the electroluminescent chip, and the position of the wavelength converter within the housing of the LED or outside the package.
• pcLEDs can be used for various outdoor lighting applications (lighting for streets, pedestrian and bicycle tracks, building facades, monuments, parks, car parking lots, and house yards) in the evening and the first part of the night.
• the aim of this invention is to develop a pcLED with a low non-visual photobiological effect, in which the partial conversion of blue light or the total conversion of near ultraviolet (UV) light in the wavelength converter would be realized in a such way that the obtained light would have a spectral component with a peak value in the 570-600 nm wavelength range and a spectral component with a peak value in the 400-500 nm wavelength range and that the ratio of the radiant fluxes of the components would be such that the chromaticity coordinates of the LED matched the black body radiation in the low CCT range ( 1 500 - 3000 ).
• the aim of the present invention is achieved by a dichromatic (blue-orange) LED that has a semiconductor chip, which emits radiation due to injection electroluminescence, and a photoluminescent converter, which is placed on the way of the photon flux emitted by the said chip.
• the converter is designed to convert the said radiation to longer wavelength radiation below 500 nm and has one type (in the case of partial conversion) or two types (in the case of complete conversion) of phosphor particles.
• the novelty is that the LED emits a blend of blue and orange light while the converter contains one of the orange phosphors listed below. This orange component together with the blue component composes a firelight SPD that is characterized by a low non-visual circadian action for humans.
• the mentioned phosphor radiating in the orange range of the spectrum can be such as: - yttrium magnesium aluminium silicon garnet, activated by trivalent cerium ions Y 3 g 2 AISi 2 0 12 :Ce 3+ ,
• the semiconductor chip generates blue light in the 400- 500 nm spectral range and the converter contains a phosphor that is characterized by the partial conversion of the said light to longer wavelength (orange) light.
• the active layer of the semiconductor chip is made of semiconductor alloy.
• the semiconductor chip In the case of complete conversion, the semiconductor chip generates near UV radiation or blue (violet) light, that has a wavelength shorter than 450 nm, and the converter contains a second phosphor which is characterized by luminescence in the 400-500 nm spectral range and that can be oxide, halo-oxide or nitride compound activated by divalent europium, divalent manganese, divalent tin or trivalent cerium ions.
• the active layer of the semiconductor chip is made of GaN semiconductor alloy or of ALGai - y N, or
• the radiant flux and the peak wavelength of each spectral component are chosen such that the final composition of the radiated light would be suitable for photobiologically friendly outdoor lighting, i.e., that its chromaticity would match that of the absolute black body radiation with a low temperature ( 1500 - 3000 K), and that the SPD would be characterized by a relatively small non-visual circadian action.
• the ratio of the radiant fluxes of the spectral components are set by adjusting the size and the concentration of phosphor particles, the width of the wavelength converter, the refraction index of the material of the wavelength converter, the distance between the wavelength converter and the electroluminescent chip, and the position of the wavelength converter within the housing of the LED or outside the package.
• the generated light spectral components have peak wavelengths as follows: ⁇ about 585 ⁇ 20 nm for the orange component,
• Fig. 1 photopic and scotopic spectral luminous efficiency functions and spectral circadian efficiency function
• Fig. 2 basic structure of LED (100) with the partial conversion of blue light for photobiologically friendly outdoor lighting;
• Fig. 3 basic structure of LED (200) with the complete conversion of near UV l ight for photobiologically friendly outdoor lighting;
• Fig. 4 typical electroluminescence spectra of a semiconductor chip containing the InGaN active layer: (a) blue 450 nm emitter; (b) near UV 365 nm emitter;
• Fig. 5 typical photoluminescence spectra of inorganic phosphors: (a) orange emitter; (b) blue emitter;
• Fig. 6 - SPDs of firelight pcLEDs for photobiologically friendly outdoor lighting (a) partial conversion LEDs with orange phosphors Y3Mg 2 AlSi 2 0i 2 :Ce 3+ , (Ba,Sr) 2 Si 5 N8:Eu 2+ , (Ba,Sr) 2 Si0 4 :Eu 2+ , Ca-a-SiAIOM:Eu 2+ , (Ca,Sr)Se:Eu 2+ ; (b) complete conversion LED with blue BaMg Al i 6 0 27 :Eu 2+ and orange Y 3 Mg 2 AlSi 2 0] 2 :Ce 3+ phosphors.
• LEDs While designing smart energy-saving lighting systems, semiconductor LEDs are more and more often applied in outdoor lighting. They are efficient and longevous, characterized by flexibility while choosing the desired SPD, suitable for rapidly switching on and off and for continuous dimming, feature no abrupt burn-out, and do not require high voltage supply; moreover they are compatible with computer-control technologies.
• the proposed two-component firelight chromaticity LED is characterized by a small non- visual circadian action and its SPD is optimized by taking into account the luminous efficacy of radiation. Since the luminous efficacy of a light source is the product of the luminous efficacy of the generated radiation and the radiant efficiency of the light source, the optimization by luminous efficacy of radiation, which depends only on SPD, is rather general. Meanwhile the radiant efficiency of LEDs depends on the injection efficiency, internal quantum efficiency, light extraction efficiency, and serial resistance, i.e. on the parameters that are gradually improving while developing LED technologies [P. Mottier, LEDs for Lighting Applications, John Wiley & Sons, Inc, London, (2009)].
• K Ko X J S(A)dA '
• S(X) is the SPD of an LED
• ⁇ is the wavelength
• V(X) is the spectral luminous efficiency function for photopic vision defined by the CIE in 1924
• KQ is the maximum possible value of luminous efficacy, which for photopic vision equals 683 Im/W.
• Photopic vision is typical for an environment where the average (adaption) luminance is above 10 cd/m . Under such conditions the sense of vision is dominated by three types of photoreceptors in the eye retina (cones) thus the photopic vision is chromatic. When the value of adaption luminance is below 0.01 cd/m 2 , the sense of vision is caused by one type of photoreceptors (rods), therefore under the conditions of low luminance humans lose the ability to distinguish colours. In this case the eye sensitivity function is described by the spectral luminous efficiency function of scotopic vision V' k), which was defined by the CIE in 1951. The maximum possible value of luminous efficacy for photopic vision is 1700 Im/W. The spectral luminous efficiency functions for photopic and scotopic vision are presented in Fig. 1.
• the proposed LED for outdoor lighting is optimized for the intermediate, i.e. mesopic, region, when the average luminance is in the range between 0.01 cd/m 2 and 10 cd/m 2 .
• This luminance range covers the interval used for the lighting of pedestrian tracks and streets which is between 0.1 cd/m 2 and 2 cd/m 2 .
• the sense of vision is determined by both cones and rods, the discrimination of colours is reduced, and the mesopic spectral luminous efficiency function Vmes ) depends on the luminance of the environment.
• the dependence of the spectral sensitivity of mesopic vision on adaption luminance is complex and is described by various models.
• the spectral luminous efficiency function is defined as:
• VmesW Mimr mVm + (1 - m)V X)
• the luminous efficacy of radiation is estimated as: where the maximum possible mesopic luminous efficacy ⁇ r mes o depends on the luminance of the environment and varies from 1700 lm/W to 683 lm/W.
• the ganglion cells that are responsible for non-visual circadian action of light are characterized by spectral sensitivity similarly to the visual receptors.
• This spectral sensitivity is described by the circadian efficiency function C(k) that is presented in Fig. 1.
• the peak of this function is seen to be at about 460 nm, thus the circadian rhythm is mostly affected by blue light [D. Gall, Circadiane Lichtgrosen und deren messtechnische Ermittlung, Licht 54, p. 1292-1297 (2002)].
• the non-visual circadian action of the proposed LED for outdoor lighting is evaluated by calculating the circadian action factor (CAF) o mes .
• This factor is defined as the ratio of the non-visual circadian efficacy of radiation to the mesopic luminous efficacy of radiation:
• K c o is equaled to 683 lm/W [A. Zukauskas, R. Vaicekauskas, P. Vitta, Optimization of solid-state lamps for photobiologically friendly mesopic lighting, Appl. Optics 51(35), p. 8423-8432 (2012)].
• the value of CAF is suitable for the comparison of the non-visual circadian action of light sources. For lighting in the evening, as low as possible Cimes value is desired since in this case a higher luminous efficacy and a lower circadian efficacy is required.
• the dichromatic light source with a short wavelength component that peaks at about 440-460 nm and with a long wavelength component that peaks at about 570-600 nm is characterized by a minimum CAF value [A. Zukauskas, R. Vaicekauskas, P. Vitta, Optimization of solid-state lamps for photobiologically friendly mesopic lighting, Appl. Optics 51(35), p. 8423-8432 (2012)].
• the SPD of the proposed LED was optimized by searching for the minimum value of CAF.
• the proposed LED for outdoor lighting is superior to common outdoor lighting sources (high and low pressure sodium vapour lamps) in colour rendering properties.
• the colour rendering can be evaluated by the general colour rendering index (CRI) R a that was introduced by CIE in 1965 and the evaluation procedure was updated in 1995 [Commission Internationale de l' Eclairage, Method of measuring and specifying colour rendering properties of light sources, Pub. CIE 13.3 : 1995].
• CRI colour rendering index
• eight main colour test samples are used; each sample is illuminated by a reference and a test light sources. After the analysis of the spectra of the reflected light, the colour differences are calculated and the special colour rendering index is found for each sample.
• the general CRI is estimated as the average of the special colour rendering indices:
• ⁇ is the average of the colour shifts of the eight samples in the CIE 1964 uniform colour space [Commission Internationale de PEclairage, Method of measuring and specifying colour rendering properties of light sources, pub. CIE 13.3: 1995].
• the maximum CRI value is 100; this value is typical of incandescent and halogen lamps.
• mesopic luminance conditions the ability of humans to distinguish colours is known to become poorer [W. R. J. Brown, The influence of luminance level on visual sensitivity to color differences, J. Opt. Soc. Am. 41, p. 684-688 (1951 )]; thus the mesopic CRI R ⁇ mes could be described somewhat differently depending on the luminance [A. Zukauskas, R. Vaicekauskas, P. Vitta, Optimization of solid-state lamps for photobiologically friendly mesopic lighting, Appl. Optics 5 1 (35), p. 8423-8432 (2012)]:
• R a ,mes 100 - A.e Y ⁇ L mes )AE, where ⁇ is the coefficient that depends on the luminance of the environment L mes .
• the proposed LED (100, 200) comprises a semiconductor chip (1 , 1 1 ) generating short- wavelength radiation with a shorter than 500 nm wavelength due to injection electroluminescence, which is placed in a reflector cup (2, 12) and is connected to terminals (3, 13) by bonded wires (4, 14).
• the chip ( 1 , 1 1 ) is covered by a wavelength converter (5, 15), which is encapsulated in a transparent package (6, 16).
• the said converter is designed for the conversion of short wavelength radiation to longer wavelength radiation due to photoluminescence for obtaining photons (10, 20, 22) and it has one type of phosphor particles (7) and two types of phosphor particles ( 17, 18) in the cases of partial conversion and complete conversion, respectively.
• the proposed LED ( 100) with the partial conversion of blue light in phosphor has a semiconductor chip ( 1 ) emitting blue light in the 400-500 nm spectral range, which is matched to the absorption spectrum of phosphor in the converter (5). A certain part of the primary flux is converted to orange light in the 570-600 nm region by an appropriate phosphor (7).
• This phosphor could be yttrium magnesium aluminium silicon garnet activated by trivalent cerium ions (Y3Mg 2 AlSi 2 0i 2 :Ce 3+ ), barium strontium silicon nitride activated by divalent europium
• the proposed LED (200) with the complete conversion of near UV light has a semiconductor chip (1 1 ) emitting near UV, violet or blue light with the wavelength shorter than 450 nm. This light is matched to the absorption spectra of phosphors and is completely absorbed in the wavelength converter.
• the converter ( 15) contains a phosphor ( 17) that converts the short-wavelength radiation to orange light in the 570-600 nm spectral range.
• the converter ( 1 5) contains another phosphor ( 18) that converts the short-wavelength radiation to blue light in the 400-500 nm spectral range.
• This phosphor could be oxide, halo-oxide or nitride compound activated by divalent europium, divalent manganese, divalent tin, or trivalent cerium ions.
• the blue component could be generated by inorganic phosphors like CaMgSi 2 0 6 :Eu 2+ , Ba 5 Si0 4 Cl 6 :Eu 2+ , Mg 3 Ca 3 (P0 4 ) 4 :Eu 2+ , (Ca,Sr,Ba) 5 (P0 4 ) 3 CI:Eu 2+ , Ca 2 B 5 0 9 (Br,Cl):Eu 2+ , BaMgAl , 0 O, 7 :Eu 2+ ,Mn 2+ ,
• the blue and the orange components are mixed with the ratio of radiant fluxes of about 1 : 15, the spectrum matching the black body radiation chromaticity is obtained, which is perceived by the human eye as a low CCT white light or firelight.
• PcLED ( 100, 200) has a semiconductor chip ( 1 , 1 1 ) of common design that is composed of a p type cladding layer, which is connected to the anode terminal, and an n type cladding layer, which is connected to the cathode terminal (3, 13).
• the electrons injected form the n type cladding layer recombine with holes injected from the p type cladding layer.
• the semiconductor chip (1 , 1 1) of the disclosed pcLEDs (100, 200) has an active layer that emits blue or near UV light.
• group III nitride compounds with the general formula A ⁇ y ⁇ n x Ga. ⁇ - ⁇ x ⁇ yN are the most convenient to use.
• the energy band-structure (side valleys are far apart) and the properties of carrier recombination in these semiconductors determine a weak dependence of the output flux on temperature.
• the most appropriate material for the active layer is the ternary alloy.
• the active layer of the proposed LED (200) with a semiconductor chip ( 1 1 ) emitting light with a wavelength shorter than 450 nm could be made of a ternary alloy (wavelength range 370 ⁇ 150 nm), a binary GaN compound (wavelength about 360 nm), or a ternary ALXjai -yN alloy (wavelength shorter than 360 nm). Also in the entire range of wavelengths, a quaternary alloy - x -yN can be used.
• the chip (1 , 1 1 ) of the LEDs (100, 200) is mounted on the reflector cup (2, 12) and using wires (4, 14) is connected to metal terminals (3, 13), through which the chip ( 1 , 1 1 ) is supplied by the driving current.
• the wavelength converter (5, 15) which is a layer of resin or silicone, a crystal or ceramic plate, or a casting of plastic that contains phosphor particles, is mounted next to the said silicon chip ( 1 , 1 1 ) in such a way that a part of or the entire photon flux generated in the semiconductor chip would be absorbed by phosphor particles.
• the converter (5, 1 5) could also be placed outside the LED package, for instance, a transparent cover of LED containing phosphor particles could also serve as a converter.
• the wavelength converter (5, 15) is designed in such a way that the wavelengths and radiant fluxes of the spectral components of LED radiation would be the most suitable for the photobiologically friendly outdoor lighting with low non-visual circadian action.
• the optimal composition of the spectrum can vary depending on a certain application (illumination of streets, car parking lots, pedestrian and bicycle tracks, building facades, monuments, parks or house yards) and on the luminance requirements.
• the radiant fluxes of each spectral component of two-spectral-component LEDs for photobiologically friendly outdoor lighting can be set by several ways.
• this is achieved by adjusting the size and concentration of the phosphor particles, the thickness of the wavelength converter, the refraction index of the material of the wavelength converter, the distance between the wavelength converter and the electroluminescent chip, and the position of the wavelength converter within the housing of the LED or outside the package.
• the optimal photobiologically friendly street lighting can be achieved when the chromaticity of LEDs matches the chromaticity of black body radiation.
• the spectral components are selected with mesopic spectral luminous efficiency and spectral circadian efficiency functions taken into account.
• the optimal peaks of the spectral components of the LED characterized by a low non-visual circadian action are at about 450 nm and 585 nm. Since the mentioned spectral efficiency functions are broadened, the indicated optimal wavelength values can differ within the ⁇ 15 nm range. Examples
• a pcLED with the partial conversion of blue light (100) for photobiologically friendly outdoor lighting is presented.
• the LED contains a semiconductor chip ( 1 ) that generates blue light due to injection electroluminescence.
• the chip is placed in a reflector cup (2) and is connected to terminals (3) by bonded wires (4).
• the chip is covered by a wavelength converter (5).
• the chip ( 1 ) and converter (5) are encapsulated within a transparent package (6) such as a plastic or silicon casting.
• the common semiconductor chip contains a p type cladding layer, which is connected to the anode terminal, and an n type cladding layer, which is connected to the cathode terminal.
• the electrons injected from the n type cladding layer recombine radiatively with the holes injected from the p type cladding layer.
• a common material for the active layer is a ternary In Gal -xN alloy with the width of the active layer and the molar fraction of indium x in the alloy chosen in such a way that the radiation band would have the peak in the 430-470 nm spectral range.
• the light generated in the semiconductor chip (1 ) passes through the wavelength converter (5), which contains phosphor particles (7).
• One part of the photons (8) emitted from the semiconductor chip are not absorbed by the phosphor particles and escape from the chip to the environment through the transparent packaging.
• Another part of the photons (9) emitted from the semiconductor chip are absorbed by the phosphor particles (7) and are converted to the photons (10) with the wavelength that matches the spectral component with the peak in the 570-600 nm (orange) spectral range.
• This kind of LED emits two-component blue-orange (low-CCT white or firelight) light.
• a pcLED (200) with the complete conversion of near UV light for photobiologically friendly outdoor lighting is presented.
• the mentioned LED (200) contains a semiconductor chip (1 1 ) that generates near UV light due to injection electroluminescence.
• the chip is placed in a reflector cup (12) and is connected to terminals ( 13) by bonded wires (14).
• the chip is covered by a wavelength converter ( 15).
• the chip ( 14) and converter (15) are encapsulated within a transparent package (16).
• the common semiconductor chip contains a p type cladding layer, which is connected to the anode terminal, and an n type cladding layer, which is connected to the cathode terminal.
• a common material for the active layer is a binary GaN semiconductor compound, or ternary IruGal -xN or AlyGal - N alloys, or a quaternary ⁇ nxA ⁇ yGa ⁇ -x-yN alloy with the width of the active layer and the molar fractions of indium x or of aluminium y in the alloy chosen in such a way, that the radiation band would have the peak with the wavelength shorter than 450 nm.
• the light generated in the semiconductor chip ( 1 1 ) passes through the wavelength converter (15), which contains the phosphor particles (17) of first type and additionally the phosphor particles ( 1 8) of second type. All photons that are emitted from the semiconductor chip are absorbed by the phosphor particles. One part of the photons ( 19) are absorbed by the first type phosphor particles ( 17) and converted to the photons (20) with the wavelength that matches the spectral component with the peak in the 570-600 nm (orange) spectral range.
• the other part of the photons (21 ) is absorbed by the second type phosphor particles (18) and is converted to the photons (22) with a wavelength that falls within 430-470 nm (blue) spectral range.
• This kind of dichromatic LED emits blue-orange (low CCT white or firelight) light.
• the possible electroluminescence spectra of semiconductor chips that are proposed for the use in pcLEDs for photobiologically friendly outdoor lighting are presented (Fig. 4).
• the electroluminescence spectra of LEDs are required to match the absorption spectra of phosphors.
• the electroluminescence spectrum of the LED has to be matched with the orange phosphor in such a way that the overall SPD would match the chromaticity of black body radiation.
• Fig. 4(a) displays the electroluminescence spectrum that corresponds to the semiconductor chip containing the active layer made of ternary In x Gai. x N alloy with the width of the active layer and indium molar fraction in the layer chosen in a such way that the radiation band peaks at 445 nm in the blue spectral range.
• This kind of chip can be used in the partial conversion LED for photobiologically friendly outdoor lighting.
• Figure 4(b) displays the electroluminescence spectrum that corresponds to the semiconductor chip containing an active layer made of ternary ln x Gai- x N alloy with the width of the active layer and indium molar fraction in the layer chosen in a such way that the radiation band peaks at 380 nm in the near UV range.
• This kind of chip can be used in the complete conversion LED for photobiologically friendly outdoor lighting.
• Fig. 5(a) displays the photoluminescence spectra that correspond to yttrium magnesium aluminium silicon garnet activated by trivalent cerium ions (Y 3 Mg 2 AISi 2 012:Ce 3+ ), barium strontium silicon nitride activated by divalent europium ions ((Ba,Sr) 2 Si 5 Ng:Eu 2+ ), barium strontium orthosilicate, activated by divalent europium ions ((Ba,Sr)Si0 4 :Eu 2+ ), calcium - alpha silicon aluminium oxynitride, activated by divalent europium ions (Ca-a-SiA10N:Eu 2+ ), or calcium strontium selenide, activated by divalent europium ions (
• phosphors can be used in the partial conversion or complete conversion pcLEDs for the photobiologically friendly outdoor lighting in order to generate the orange spectral component.
• Fig. 5(b) displays the photoluminescence spectrum that corresponds to aluminate phosphor activated by divalent europium ions (BaMgAlioO
• divalent europium ions BaMgAlioO
• Such phosphor can be used in the complete conversion pcLEDs for the photobiologically friendly outdoor lighting for the generation of the blue spectral component.
• the SPDs of the partial and complete conversion pcLEDs for photobiologically friendly outdoor lighting are presented in Fig. 6.
• the spectra have the blue component with the peak in the 430-470 nm range that is generated by the InGaN semiconductor chip due to injection electroluminescence or by the wavelength converter due to photoluminescence and the orange component generated due to the photoluminescence of the wavelength converter.
• the radiation fluxes of residual blue light and of light that is generated by each phosphor are set by adjusting the concentration of the phosphor particles, the width of the wavelength converter, the refraction index of the material of the wavelength converter, and the position of the wavelength converter within the housing of the LED or outside the package. Accordingly, Fig.
• 6(a) presents the SPDs that correspond to two-component light that has the firelight chromaticity and that is generated using the partial conversion of blue light with the spectral component that peaks at 445- ⁇ 50 nm in Y 3 Mg 2 AISi 2 0 12 :Ce 3+ , (Ba,Sr) 2 Si 5 N 8 :Eu 2+ , (Ba,Sr) 2 Si0 4 :Eu 2+ , Ca-a-SiA10N:Eu 2+ and (Ca,Sr)Se:Eu 2+ phosphors emitting orange light with the spectral component due to the photoluminescence that peaks at 570-600 nm. Accordingly, Fig.
• 6(b) displays the SPD that corresponds to two-component light that has firelight chromaticity and that is generated using the complete conversion of near UV light in BaMgAl mOnrEu 2 " and Y 3 Mg 2 AlSi 2 0
• Such firelight pcLEDs can be used in the evening illumination of streets, car parking lots, pedestrian and bicycle tracks, buildings, monuments, parks and house yards in order to avoid the disruption of the human circadian rhythm.
• Table 1 presents photometric, chromatic, and photobiological parameters of the pcLED.
• Table 1 presents parameters of the pcLED examples that are compared to the parameters of commercial warm white and cool white LEDs and of the standard CIE illuminant A: CCT (correlated colour temperature), CAF (circadian action factor), LER (luminous efficacy of radiation), CRI (colour rendering index), CRI mes (mesopic colour rendering index), and rj (maximum efficiency that is determined by the wavelength difference of light emitted by the semiconductor chip and phosphor (Stokes shift).
• the parameters of the pcLEDs presented in Table 1 are also compared to the parameters of the widely used high pressure sodium (HPS) lamp.
• HPS high pressure sodium
• the values are given for the luminance of the environment of 0.3 and 2 cd/m 2 (the lowest class ME6 and the highest class ME 1 of street lighting standards, respectively).
• the CAF values normalized to the CIE standard illuminant A 2856 black body radiation
• Table 1 shows that the parameters of light sources strongly depend on the selected phosphor. However, the common tendency is that for increased CCT values, the CAF is also increasing.
• the values of the luminous efficacy of radiation for the SPDs of the proposed LEDs are somewhat lower than those of commercial LEDs and HPS lamps.
• the CAF of the proposed LEDs when the luminance of the environment is 2 cd/m 2 , the CAF of the proposed LEDs is by about 0.1-0.25 blm/lm lower than that of the commercial warm white LEDs and even by 0.3-0.45 blm/lm lower than that of the commercial cool white LEDs.
• the CAF value of the proposed LEDs normalized to that of the CIE standard illuminant A is no larger than 0.6
• the normalized CAF is about 0.85 and 1 .4, respectively.
• the colour rendering properties of the proposed LEDs are comparable to those of the commercial LEDs and significantly surpass those of the HPS lamp.
• the maximum efficiency values of the commercial warm white LED and of the proposed LEDs are very similar. However, due to the smaller Stokes shift, the commercial cool white LED is characterized by a higher maximum efficiency.
• the short wavelength and long wavelength components of light generated by the proposed partial conversion LEDs have partial radiant flux ratios as follows:
• the used phosphor is Y3Mg 2 AlSi 2 0i2:Ce 3+
• the light emitted by the InGaN chip has a spectral peak at 440 nm
• the CCT of the obtained SPD is 2088
• the CAF normalized to the CIE standard illuminant A equals 0.379 for the luminance of the environment 2 cd/m 2 ;
• the short wavelength and the long wavelength components of light generated by the proposed complete conversion LEDs have partial radiant flux ratios as follows: - about 1 : 19, when the used phosphor is Y 3 Mg 2 AlSi 2 0 I 2 :Ce 3+ , the CCT of the obtained SPD is 2100 , and the CAF normalized to the CIE standard illuminant A equals 0.398 for the luminance of the environment 2 cd/m 2 ;

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