Browsing by Author "Huang, Chien-Hao"

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A Novel Single-Composition Trichromatic White-Light Ca(3)Y(GaO)(3)(BO(3))(4):Ce(3+),Mn(2+),Tb(3+) Phosphor for UV-Light Emitting Diodes
(2011-02-10)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
A novel single-composition white-emitting phosphor Ca(3)Y(GaO)(3)(BO(3))(4):Ce(3+), Mn(2+),Tb(3+) has been synthesized by a high-temperature solid-state reaction. The spectral overlap between the emission band of Ce(3+) and the excitation band of Mn(2+), which supports the occurrence of the energy transfer from Ce(3+) to Mn(2+), has been studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism. Because there was no spectral overlap between the emission spectra of Ce(3+) and excitation band of Tb(3+) in our study, no energy transfer from Ce(3+) to Tb(3+) was observed, Indicating that Ce(3+) and Tb(3+) were coexcited. Through effective resonance-type energy transfer and coexcitation, the chromaticity coordinates of Ca(3)Y(GaO)(3)(BO(3))(4):Ce(3+),Mn(2+),Tb(3+) phosphors can be tuned from (0.152, 0.061) for Ca(3)Y-(GaO)(3)(BO(3))(4):Ce(3+) to (0.562, 0.408) for Ca(3)Y(GaO)(3)(BO(3))(4):Mn(2+), and eventually reaching (0.314, 0.573) for Ca(3)Y(GaO)(3)(BO(3))(4):Tb(3+). A white light-emitting diode (LED) was fabricated by using the white-emitting single-composition (Ca(0.97))(3)(Y(0.92))(GaO)(3)(BO(3))(4):0.01Ce(3+),-0.03Mn(2+),0.07Tb(3+) pumped by a 365 nm UV-chip. Our results indicated that the CIE chromaticity coordinates and correlated color temperature (CCT) for white UV-LEDs were (0.31, 0.33) and 6524 K, respectively. Therefore, our novel white Ca(3)Y(GaO)(3)(BO(3))(4):Ce(3+),Mn(2+),Tb(3+) can serve as a key material for phosphor-converted white-light UV-LEDs.
A Novel Single-Composition Trichromatic White-Light Ca3Y(GaO)(3)(BO3)(4):Ce3+,Mn2+,Tb3+ Phosphor for UV-Light Emitting Diodes
(2011-02-10)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
A novel single-composition white-emitting phosphor Ca3Y(GaO)(3)(BO3)(4):Ce3+, Mn2+,Tb3+ has been synthesized by a high-temperature solid-state reaction. The spectral overlap between the emission band of Ce3+ and the excitation band of Mn2+, which supports the occurrence of the energy transfer from Ce3+ to Mn2+, has been studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism. Because there was no spectral overlap between the emission spectra of Ce3+ and excitation band of Tb3+ in our study, no energy transfer from Ce3+ to Tb3+ was observed, Indicating that Ce3+ and Tb3+ were coexcited. Through effective resonance-type energy transfer and coexcitation, the chromaticity coordinates of Ca3Y(GaO)(3)(BO3)(4):Ce3+,Mn2+,Tb3+ phosphors can be tuned from (0.152, 0.061) for Ca3Y-(GaO)(3)(BO3)(4):Ce3+ to (0.562, 0.408) for Ca3Y(GaO)(3)(BO3)(4):Mn2+, and eventually reaching (0.314, 0.573) for Ca3Y(GaO)(3)(BO3)(4):Tb3+. A white light-emitting diode (LED) was fabricated by using the white-emitting single-composition (Ca-0.97)(3)(Y-0.92)(GaO)(3)(BO3)(4):0.01Ce(3+),-0.03Mn(2+),0.07Tb(3+) pumped by a 365 nm UV-chip. Our results indicated that the CIE chromaticity coordinates and correlated color temperature (CCT) for white UV-LEDs were (0.31, 0.33) and 6524 K, respectively. Therefore, our novel white Ca3Y(GaO)(3)(BO3)(4):Ce3+,Mn2+,Tb3+ can serve as a key material for phosphor-converted white-light UV-LEDs.
A Single-Phased Emission-Tunable Phosphor Ca(9)Y(PO(4))(7):Eu(2+),Mn(2+) with Efficient Energy Transfer for White-Light-Emitting Diodes
(2010-01-01)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
Liu, Wei-Ren
;
Chiu, Yi-Chen
;
Yeh, Yao-Tsung
A series of single-composition emission-tunable Ca(9)Y(PO(4))(7):Eu(2+),Mn(2+) phosphors were synthesized by solid-state reaction. The energy transfer from Eu(2+) to Mn(2+) in Ca(9)Y(PO(4))(7) host matrix was studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism with the critical distance of similar to 11 angstrom. The wavelength-tunable white light can be realized by coupling the emission bands centered at 486 and 638 nm ascribed to the contribution From Eu(2+) and Mn(2+), respectively. By properly tuning the relative composition of Eu(2+)/Mn(2+), chromaticity coordinates of (0.31, 0.33) can be achieved under excitation at 250-440 nm. Moreover, white-light-emitting diodes were fabricated through the integration of 365 nm chips and single composition white-light-emitting phosphors (Ca(0.975)Eu(0.01)Mn(0.015))(9)Y(PO(4))(7) into a single package shows a cool white light of 7200 K, color rendering index of 76, and color coordinates of (0.30, 0.31) close to that of ideal white light can be achieved.
A Single-Phased Emission-Tunable Phosphor Ca9Y(PO4)(7):Eu2+,Mn2+ with Efficient Energy Transfer for White-Light-Emitting Diodes
(2010-01-01)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
Liu, Wei-Ren
;
Chiu, Yi-Chen
;
Yeh, Yao-Tsung
A series of single-composition emission-tunable Ca9Y(PO4)(7):Eu2+,Mn2+ phosphors were synthesized by solid-state reaction. The energy transfer from Eu2+ to Mn2+ in Ca9Y(PO4)(7) host matrix was studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism with the critical distance of similar to 11 angstrom. The wavelength-tunable white light can be realized by coupling the emission bands centered at 486 and 638 nm ascribed to the contribution From Eu2+ and Mn2+, respectively. By properly tuning the relative composition of Eu2+/Mn2+, chromaticity coordinates of (0.31, 0.33) can be achieved under excitation at 250-440 nm. Moreover, white-light-emitting diodes were fabricated through the integration of 365 nm chips and single composition white-light-emitting phosphors (Ca0.975Eu0.01Mn0.015)(9)Y(PO4)(7) into a single package shows a cool white light of 7200 K, color rendering index of 76, and color coordinates of (0.30, 0.31) close to that of ideal white light can be achieved.
An Investigation on the Luminescence and Ce(3+) -> Eu(2+) Energy Transfer in Ca(9)Y(PO(4))(7):Ce(3+),Eu(2+) Phosphor
(2011-01-01)
Huang, Chien-Hao
;
Luo, Liyang
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
A series of Ce(3+)- and Eu(2+)-coactivated Ca(9)Y(PO(4))(7) phosphors were synthesized by high temperature solid-state reactions. The Ca(9)Y(PO(4))(7):Ce(3+), Eu(2+) phosphor showed two emission bands under 292 nm excitation:the one observed at 342 nm was attributed to the 4f(0)5d(1) -> 4f(1) transition of Ce(3+) ion emission, and the other found at 492 nm was assigned to the 4 f(6)5d(1) -> 4f(7) transition of Eu(2+) ions. Through an effective resonance-type energy transfer, the Ca(9)Y(PO(4))(7):Ce(3+), Eu(2+) phosphors exhibit a systematically varied hues from ultraviolet to blue-greenish and the relative intensity of ultraviolet and blue-greenish emissions can be tuned by properly tuning the relative dopant composition of Ce(3+)/Eu(2+). The energy transfer from a sensitizer Ce(3+) to an activator Eu(2+) in Ca(9)Y(PO(4))(7) host matrix was studied and demonstrated to be a resonant type via a dipole-dipole mechanism based on the decay lifetime analysis. Furthermore, we have calculated the critical distance for Ce(3+) -> Eu(2+) energy transfer to be about 30.7 angstrom by both concentration quenching and spectral overlap methods. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.029111jes] All rights reserved.
An Investigation on the Luminescence and Ce3+ -> Eu2+ Energy Transfer in Ca9Y(PO4)(7):Ce3+,Eu2+ Phosphor
(2011-01-01)
Huang, Chien-Hao
;
Luo, Liyang
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
A series of Ce3+- and Eu2+-coactivated Ca9Y(PO4)(7) phosphors were synthesized by high temperature solid-state reactions. The Ca9Y(PO4)(7):Ce3+, Eu2+ phosphor showed two emission bands under 292 nm excitation:the one observed at 342 nm was attributed to the 4f(0)5d(1) -> 4f(1) transition of Ce3+ ion emission, and the other found at 492 nm was assigned to the 4 f(6)5d(1) -> 4f(7) transition of Eu2+ ions. Through an effective resonance-type energy transfer, the Ca9Y(PO4)(7):Ce3+, Eu2+ phosphors exhibit a systematically varied hues from ultraviolet to blue-greenish and the relative intensity of ultraviolet and blue-greenish emissions can be tuned by properly tuning the relative dopant composition of Ce3+/Eu2+. The energy transfer from a sensitizer Ce3+ to an activator Eu2+ in Ca9Y(PO4)(7) host matrix was studied and demonstrated to be a resonant type via a dipole-dipole mechanism based on the decay lifetime analysis. Furthermore, we have calculated the critical distance for Ce3+ -> Eu2+ energy transfer to be about 30.7 angstrom by both concentration quenching and spectral overlap methods. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.029111jes] All rights reserved.
An organic hydrogel film with micron-sized pillar array for real-time and indicator-free detection of Zn(2+)
(2011-11-01)
Chao, Yu-Chiang
;
Huang, Yi-Sa
;
Wang, Hsin-Ping
;
Fu, Ssu-Ming
;
Huang, Chien-Hao
A hydrogel sensing film for a real-time and indicator-free detection of Zn(2+) is developed by embedding a fluorescent indicator 11,16-bis( phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene in a hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film shows high stability and selectivity to Zn(2+). The sensitivity of the sensing film is increased by fabricating a micron-sized pillar array on the surface of the sensing film to increase the surface area. For Zn(2+) concentrations of 10 (4) and 10 (3) M, the response time is 30 and 3 s, respectively. (C) 2011 Elsevier B.V. All rights reserved.
An organic hydrogel film with micron-sized pillar array for real-time and indicator-free detection of Zn2+
(2011-11-01)
Chao, Yu-Chiang
;
Huang, Yi-Sa
;
Wang, Hsin-Ping
;
Fu, Ssu-Ming
;
Huang, Chien-Hao
A hydrogel sensing film for a real-time and indicator-free detection of Zn2+ is developed by embedding a fluorescent indicator 11,16-bis( phenyl)-6,6,21,21-tetramethyl-m-benzi-6,21-porphodimethene in a hydrogel host poly(2-hydroxyethyl methacrylate). The sensing film shows high stability and selectivity to Zn2+. The sensitivity of the sensing film is increased by fabricating a micron-sized pillar array on the surface of the sensing film to increase the surface area. For Zn2+ concentrations of 10 (4) and 10 (3) M, the response time is 30 and 3 s, respectively. (C) 2011 Elsevier B.V. All rights reserved.
Anomalous luminescence from Yb2+-doped Ca2PO4Cl
(2014-04-01)
Wang, De-Yin
;
Chiu, Yi-Chen
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Huang, Chien-Hao
;
Wu, Yun-Chen
;
Chen, Teng-Ming
The photoluminescence of Ca2PO4Cl:Yb2+ has been investigated and compared with that of Ca2PO4Cl: Eu2+, and the application of Ca2PO4Cl:Yb2+ for white LED has been evaluated. The excitation spectra of Ca2PO4Cl:Yb2+ are dominated by an intense excitation band at 395 nm. Under near DV excitation at 395 nm, Ca2PO4Cl:Yb2+ shows a broad asymmetric emission with maximum at 490 nm. This emissions result from two different Yb2+ centers is evidenced by the low temperature (T=100 K) emission spectrum. Yb2+ luminescence differs significantly from that of Eu2+, most notably in the structure of emission spectra, and is characterized by a much broader emission band and lower quenching temperature. Such anomalous luminescence from Yb2+ is ascribed to the de-excitation process of the Yb2+-trapped exciton state. Ca2PO4Cl:Yb2+ has external quantum efficiency of 24% and exhibits 40% of luminescence quenching at 100 degrees C in the air and, therefore, these results reveal its limited potential in the fabrication of white-light LEDs. (C) 2013 Elsevier B.V. All rights reserved.
(Ba,Sr)Y(2)Si(2)Al(2)O(2)N(5):Eu(2+): a novel near-ultraviolet converting green phosphor for white light-emitting diodes
(2011-01-01)
Liu, Wei-Ren
;
Yeh, Chiao-Wen
;
Huang, Chien-Hao
;
Lin, Chun Che
;
Chiu, Yi-Chen
A highly intense green-emitting phosphor BaY(2)Si(2)Al(2)O(2)N(5) : Eu(2+) (BYN : Eu(2+)) peaking at 511 nm was synthesized by a solid state reaction. The structure refinement, luminescence properties of BYN : Eu(2+) phosphors as well as their thermal quenching and the fabrication of white-light-emitting diodes (W-LEDs) were firstly investigated. By partially substituting Ba by Sr, namely (Ba, Sr)Y(2)Si(2)Al(2)O(2)N(5) : Eu(2+) (BSYN : Eu(2+)), the emission peak was shifted to 565 nm, giving a yellow-orange color, due to the splitting of the 5d energy level. By utilizing a mixture of blue-emitting BaMgAl(10)O(17) : Eu(2+), green-emitting BYN : Eu(2+) and red-emitting CaAlSiN(3) : Eu(2+) phosphors as light converters, an intense white GaN-based n-UV-LED (380 nm) was fabricated to a exhibit good color-rendering index R(a) of 84.5 at a correlated color temperature of 5089 K and CIE coordinates of (0.3425, 0.3478). Based on these results, we are currently evaluating the potential application of BYN : Eu(2+) as a green-emitting near-UV convertible phosphor.
(Ba,Sr)Y2Si2Al2O2N5:Eu2+: a novel near-ultraviolet converting green phosphor for white light-emitting diodes
(2011-01-01)
Liu, Wei-Ren
;
Yeh, Chiao-Wen
;
Huang, Chien-Hao
;
Lin, Chun Che
;
Chiu, Yi-Chen
A highly intense green-emitting phosphor BaY2Si2Al2O2N5 : Eu2+ (BYN : Eu2+) peaking at 511 nm was synthesized by a solid state reaction. The structure refinement, luminescence properties of BYN : Eu2+ phosphors as well as their thermal quenching and the fabrication of white-light-emitting diodes (W-LEDs) were firstly investigated. By partially substituting Ba by Sr, namely (Ba, Sr)Y2Si2Al2O2N5 : Eu2+ (BSYN : Eu2+), the emission peak was shifted to 565 nm, giving a yellow-orange color, due to the splitting of the 5d energy level. By utilizing a mixture of blue-emitting BaMgAl10O17 : Eu2+, green-emitting BYN : Eu2+ and red-emitting CaAlSiN3 : Eu2+ phosphors as light converters, an intense white GaN-based n-UV-LED (380 nm) was fabricated to a exhibit good color-rendering index R-a of 84.5 at a correlated color temperature of 5089 K and CIE coordinates of (0.3425, 0.3478). Based on these results, we are currently evaluating the potential application of BYN : Eu2+ as a green-emitting near-UV convertible phosphor.
BaZrSi(3)O(9):Eu(2+): a cyan-emitting phosphor with high quantum efficiency for white light-emitting diodes
(2011-01-01)
Wang, De-Yin
;
Huang, Chien-Hao
;
Wu, Yun-Chen
;
Chen, Teng-Ming
;
應用化學系
In this paper, a cyan-emitting phosphor BaZrSi(3)O(9):Eu(2+) was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 380-420 nm region, and the emission intensity of the optimized BaZrSi(3)O(9):Eu(2+) was found to be 90% and 198% of that of the commercial BaMgAl(10)O(17):Eu(2+) (BAM:Eu(2+)) under excitation at 405 nm and 420 nm, respectively. Upon excitation at 405 nm, the quantum efficiency of the optimized BaZrSi(3)O(9):Eu(2+) is 83% of that of BAM:Eu(2+). The performance of this phosphor was further tested to fabricate white LED lamps. By coating BaZrSi(3)O(9):Eu(2+) with a green-emitting (Ba,Sr)(2)SiO(4):Eu(2+) and a red-emitting CaAlSiN(3):Eu(2+) on a near-ultraviolet (405 nm) LED chip, driven by a 350 mA forward bias current, intense warm white light with a color rendering index of 90 has been produced.
BaZrSi3O9:Eu2+: a cyan-emitting phosphor with high quantum efficiency for white light-emitting diodes
(2011-01-01)
Wang, De-Yin
;
Huang, Chien-Hao
;
Wu, Yun-Chen
;
Chen, Teng-Ming
;
應用化學系
In this paper, a cyan-emitting phosphor BaZrSi3O9:Eu2+ was synthesized and evaluated as a candidate for white light emitting diodes (WLEDs). This phosphor shows strong and broad absorption in 380-420 nm region, and the emission intensity of the optimized BaZrSi3O9:Eu2+ was found to be 90% and 198% of that of the commercial BaMgAl10O17:Eu2+ (BAM:Eu2+) under excitation at 405 nm and 420 nm, respectively. Upon excitation at 405 nm, the quantum efficiency of the optimized BaZrSi3O9:Eu2+ is 83% of that of BAM:Eu2+. The performance of this phosphor was further tested to fabricate white LED lamps. By coating BaZrSi3O9:Eu2+ with a green-emitting (Ba,Sr)(2)SiO4:Eu2+ and a red-emitting CaAlSiN3:Eu2+ on a near-ultraviolet (405 nm) LED chip, driven by a 350 mA forward bias current, intense warm white light with a color rendering index of 90 has been produced.
Ca(9)La(PO(4))(7):Eu(2+),Mn(2+): an emission-tunable phosphor through efficient energy transfer for white light-emitting diodes
(2010-03-01)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
We have synthesized a series of single-composition emission-tunable Ca(9)La(PO(4))(7):Eu(2+),Mn(2+) (CLP:Eu(2+),Mn(2+)) phosphors by solid state reactions. Through an effective resonance-type energy transfer, the CLP:Eu(2+),Mn(2+) phosphors exhibit a systematically varied hues from green, yellow, and eventually to red and the relative intensity of green and red emissions can be tuned by adjusting the concentration of Mn(2+), respectively. The energy transfer from Eu(2+) to Mn(2+) in CLP:Eu(2+),Mn(2+) has been studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism based on the decay lifetime data and the energy transfer critical distance was estimated to be 11.36 angstrom by using the spectral overlap methods. A warm white light emitting diode (WLED) with CIE chromaticity coordinates of (0.35, 0.31), superior color-rendering index (Ra) of 91.5 and lower correlated color temperature (CCT) of 4,496 K was fabricated by combining a 365 nm UV-InGaN chip and a phosphor blend of yellow-emitting (Ca(0.98)Eu(0.005)Mn(0.015))(9)La(PO(4))(7) and blue-emitting BaMgAl(10)O(17):Eu(2+). (C) 2010 Optical Society of America
(Ca,Mg,Sr)(9)Y(PO(4))(7):Eu(2+),Mn(2+): Phosphors for white-light near-UV LEDs through crystal field tuning and energy transfer
(2011-01-01)
Huang, Chien-Hao
;
Wu, Pin-Jiun
;
Lee, Jyh-Fu
;
Chen, Teng-Ming
;
應用化學系
Two series of single-composition (Ca,Mg,Sr)(9)Y(PO(4))(7):Eu(2+) and (Ca(0.5)Sr(0.5))(9)Y(PO(4))(7):Eu(2+),Mn(2+) phosphors were synthesized via high-temperature solid-state reactions. Their emission colors could be tuned from blue to green and eventually to red through tuning the crystal field splitting and energy transfer. On examining the Mn(2+) concentration-dependent photoluminescence properties, we found that co-doping with Mn(2+) would lead to a change in Eu(2+)/Eu(3+) ratio. Moreover, an energy transfer from Eu(2+) to Mn(2+) occurs because of the spectral overlap between the emission band of Eu(2+) and the excitation band of Mn(2+). The resonance-type energy transfer via a dipole-quadrupole interaction mechanism was supported by decay lifetime data and the critical distance of energy transfer was calculated to be 11.09 angstrom A. A trichromatic white-light emitting diode was fabricated by integrating a 380 nm near-ultraviolet (n-UV) chip comprising yellow-emitting (Ca(0.5)Sr(0.5))(9)Y (PO(4))(7):0.007Eu(2+),0.02Mn(2+) and blue-emitting (Ca(0.5)Mg(0.5))(9)Y(PO(4))(7):0.007Eu(2+) phosphors into a single package. Such a composite device emitted white light with a correlated color temperature of 6303 K, a color rendering index of 87.4, and color coordinates (0.314, 0.348) close to those of ideal white light. The results suggest that a phosphor blend of (Ca(0.5)Sr(0.5))(9)Y(PO(4))(7):0.007Eu(2+), 0.02Mn(2+) and (Ca(0.5)Mg(0.5))(9)Y(PO(4))(7):0.007Eu(2+) is potentially useful for white n-UV light-emitting diodes (LEDs).
(Ca,Mg,Sr)(9)Y(PO4)(7):Eu2+,Mn2+: Phosphors for white-light near-UV LEDs through crystal field tuning and energy transfer
(2011-01-01)
Huang, Chien-Hao
;
Wu, Pin-Jiun
;
Lee, Jyh-Fu
;
Chen, Teng-Ming
;
應用化學系
Two series of single-composition (Ca,Mg,Sr)(9)Y(PO4)(7):Eu2+ and (Ca0.5Sr0.5)(9)Y(PO4)(7):Eu2+,Mn2+ phosphors were synthesized via high-temperature solid-state reactions. Their emission colors could be tuned from blue to green and eventually to red through tuning the crystal field splitting and energy transfer. On examining the Mn2+ concentration-dependent photoluminescence properties, we found that co-doping with Mn2+ would lead to a change in Eu2+/Eu3+ ratio. Moreover, an energy transfer from Eu2+ to Mn2+ occurs because of the spectral overlap between the emission band of Eu2+ and the excitation band of Mn2+. The resonance-type energy transfer via a dipole-quadrupole interaction mechanism was supported by decay lifetime data and the critical distance of energy transfer was calculated to be 11.09 angstrom A. A trichromatic white-light emitting diode was fabricated by integrating a 380 nm near-ultraviolet (n-UV) chip comprising yellow-emitting (Ca0.5Sr0.5)(9)Y (PO4)(7):0.007Eu(2+),0.02Mn(2+) and blue-emitting (Ca0.5Mg0.5)(9)Y(PO4)(7):0.007Eu(2+) phosphors into a single package. Such a composite device emitted white light with a correlated color temperature of 6303 K, a color rendering index of 87.4, and color coordinates (0.314, 0.348) close to those of ideal white light. The results suggest that a phosphor blend of (Ca0.5Sr0.5)(9)Y(PO4)(7):0.007Eu(2+), 0.02Mn(2+) and (Ca0.5Mg0.5)(9)Y(PO4)(7):0.007Eu(2+) is potentially useful for white n-UV light-emitting diodes (LEDs).
Ca9La(PO4)(7):Eu2+,Mn2+: an emission-tunable phosphor through efficient energy transfer for white light-emitting diodes
(2010-03-01)
Huang, Chien-Hao
;
Chen, Teng-Ming
;
應用化學系
;
Department of Applied Chemistry
We have synthesized a series of single-composition emission-tunable Ca9La(PO4)(7):Eu2+,Mn2+ (CLP:Eu2+,Mn2+) phosphors by solid state reactions. Through an effective resonance-type energy transfer, the CLP:Eu2+,Mn2+ phosphors exhibit a systematically varied hues from green, yellow, and eventually to red and the relative intensity of green and red emissions can be tuned by adjusting the concentration of Mn2+, respectively. The energy transfer from Eu2+ to Mn2+ in CLP:Eu2+,Mn2+ has been studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism based on the decay lifetime data and the energy transfer critical distance was estimated to be 11.36 angstrom by using the spectral overlap methods. A warm white light emitting diode (WLED) with CIE chromaticity coordinates of (0.35, 0.31), superior color-rendering index (Ra) of 91.5 and lower correlated color temperature (CCT) of 4,496 K was fabricated by combining a 365 nm UV-InGaN chip and a phosphor blend of yellow-emitting (Ca0.98Eu0.005Mn0.015)(9)La(PO4)(7) and blue-emitting BaMgAl10O17:Eu2+. (C) 2010 Optical Society of America
CaY2Si2S8:Ce3+: a novel green-emitting thiosilicate phosphor for white light-emitting diodes
(2014-11-14)
Lee, Szu-Ping
;
Huang, Chien-Hao
;
Chen, Teng-Ming
;
應用化學系
;
應用化學系分子科學碩博班
A novel green-emitting Ce3+-doped CaY2Si2S8 thiosilicate phosphor was synthesized by using solid-state methods in a sealed silica ampoule. This compound could be excited over a broad range from UV to blue light (400-450 nm) and generated a broadband emission peaking at similar to 495 nm, with a quantum efficiency of similar to 57%, which is promising for solid-state lighting applications. Temperature-dependent optical measurements of CaY2Si2S8:Ce3+ from 25 to 225 degrees C were performed. In addition, a white LED device was fabricated by using the green-emitting CaY2Si2S8:Ce3+ phosphor and commercially-available red-emitting CaAlSiN3:Eu2+ pumped with a 450 nm blue chip. The CRI value and CCT were measured to be 91-95 and 3800-8600 K, respectively, showing promising potential for solid-state lighting applications. The preparation, spectroscopic characterization, quantum efficiency, decay lifetime, thermal stability, and related LED device data are also presented.
Charge transfer luminescence of hafnates under synchrotron vacuum ultraviolet excitation
(2014)
Wang, De-Yin
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Huang, Chien-Hao
;
Cheng, Bing-Ming
;
Chen, Teng-Ming
;
Wang, Yu-Hua
Under synchrotron vacuum ultraviolet excitation, three different hafnates (BaHf(PO4)(2), BaHf(BO3)(2) and BaHfSi3O9) show self-activated luminescence with peaks ranging from 275-335 nm, which is attributed to the charge-transfer luminescence from the hafnate (HfO68-) group. Upon doping Eu2+ into BaHfSi3O9, host sensitization of Eu2+ emission via hafnate intrinsic emission is demonstrated.
Crystal structure of blue-white-yellow color-tunable Ca4Si2O7F2:Eu2+,Mn2+ phosphor and investigation of color tunability through energy transfer for single-phase white-light near-ultraviolet LEDs
(2012)
Huang, Chien-Hao
;
Chan, Ting-Shan
;
Liu, Wei-Ren
;
Wang, De-Yin
;
Chiu, Yi-Chen
The crystal structure of Ca4Si2O7F2:Eu2+,Mn2+ was refined and determined from X-ray diffraction (XRD) profiles obtained using a synchrotron light source by the Rietveld refinement method. It was found to crystallize into a monoclinic structure with the P2(1)/c(14) space group. On examining the Mn2+-concentration-dependent photoluminescence properties, we found that the emission colors could be tuned from blue (0.152, 0.112) to white-light (0.351, 0.332) and eventually to yellow (0.430, 0.423) through energy transfer by changing the Eu2+/Mn2+ ratio. Moreover, energy transfer from a sensitizer Eu2+ to an activator Mn2+ occurs via a resonance-type dipole-quadrupole interaction mechanism, and the critical distances of the energy transfer were calculated to be 11.66 angstrom and 12.61 angstrom using concentration quenching and spectral overlap methods, respectively. Combining a 400 nm near-ultraviolet (NUV) chip and a single-phase white-emitting (Ca0.96Eu0.01Mn0.03)(4)Si2O7F2 phosphor produced a white-light NUV LED with CIE chromaticity coordinates of (0.347, 0.338) and a warm color temperature of 4880 K.