Full-color emission generation from single phased phosphor Sr10[(PO4)5.5(BO4)0.5](BO2): Ce3+, Mn2+, Tb3+ for white light emitting diodes

Ge Zhu; Zhipeng Ci; Qian Wang; Yurong Shi; Yuhua Wang

doi:10.1364/OME.3.001810

1. Introduction

In the last few decades, there has been a phenomenal growth in investigation of the field of luminescence, and significant progress has been made in solid state lighting [1,2]. The breakthrough in the development of high performance light-emitting diodes (LEDs) via improvement in both internal quantum efficiency [3–7] and extraction efficiency [8,9] has resulted in practical excitation sources applicable for phosphor-converted white LEDs. Currently, phosphor-converted (pc) white light-emitting diodes (LEDs), with characteristics of high efficiency, long lifetime, and energy saving, have attracted more and more attention [10,11]. By virtue of these advantages, white LEDs are currently the mainstream in the market and are being widely used in not only point light sources, but also wide-illumination equipment, back-lighting of liquid-crystal TVs and high-power automotive headlights [12]. In pc-white LEDs, phosphors are the key component to down-convert near-ultraviolet (n-UV)/ blue pump light from InGaN LEDs into visible light. To date, the most dominant pc-white LEDs is combination of a blue LED with a yellow phosphor ((Y,Gd)₃(Al,Ga)₅O₁₂:Ce³⁺). Such generated light color is not true because this system lacks of a red emitting component, which restricts their use in more vivid applications [13,14]. In order to obtain a warm white light, the new technologies are based on the combination of a near-ultraviolet/ultraviolet (n-UV/UV) LED chip with three phosphors emitting red, green, and blue (RGB) colors [15,16]. However, different phosphors experience different light output degradation rates, leading to unstable white light, and poor luminous efficiency attributed to reabsorption has commonly been encountered [17]. Therefore, this type white LEDs still face large challenges. For these reasons, people are making more efforts in developing a full-color emitting phosphor based on a single host to avoid the intrinsic color balance, device complication, and high-cost problems. One of the strategies for generating white light from single-phased phosphors is by codoping sensitizer and activator into the same host, such as Eu²⁺ to Mn²⁺ ion [18], Ce³⁺ to Tb³⁺ ion [19], or Ce³⁺ to Mn²⁺ ion [20].

In recent years, the luminescent properties of phosphate materials have been widely investigated as a result of certain advantages, such as excellent thermal and chemical stability [21], and development of optical devices based on rare earth ion doped materials is one of the most interesting fields of research. Phosphates phosphors are widely investigated because of their low cost, high stability for use in solid state lighting applications, and their important crystallographic possibilities for accommodating luminescent ions [22]. So in this paper, we choose strontium phosphate orthoborate metaborate Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂) (SPB) as host and synthesized rare earth ion Ce³⁺, Tb³⁺ and Mn²⁺ co-doped SPB phosphors, with an aim to realize warm white light emission in this single phased phosphor. As excepted, the color tunable full-color emitting phosphor SPB: Ce³⁺, Mn²⁺, Tb³⁺ was obtained by adjusting the related contents of Tb³⁺ and Mn²⁺ based on the efficient resonant energy transfer. In addition, the energy transfer mechanism was also discussed in detail in SPB: Ce³⁺, Mn²⁺, Tb³⁺ through photoluminescence spectra and decay times. At the same time, the color rendering index (CRI) and correlated color temperature (CCT) were also studied to evaluate the quality of the white light emission.

2. Experimental

2.1 Materials and synthesis

All the powder samples were synthesized by traditional solid-state reaction method. The starting materials were SrCO₃ (A.R. 99.9%), (NH₄)₂HPO₄ (A.R. 99.9%), H₃BO₃ (A.R. 99.9%), MnCO₃ (A.R. 99.9%), CeO₂ (A.R. 99.99%) and Tb₄O₇ (A.R. 99.99%). The stoichiometric raw materials were ground thoroughly in an agate mortar and then heated to 773 K in air for 3h. Subsequently the preheated mixture was ground again and fired to 1423 K for 8 h in an alumina crucible under N₂-H₂ (8%) atmosphere in horizontal tube furnaces. Finally the as-synthesized samples were slowly cooled to room temperature inside the tube furnace under H₂-N₂ flow.

2.2 Measurements and characterization

The crystal structure of the synthesized samples was identified by using a Rigaku D/Max-2400 X-ray diffractometer (XRD) with Nifiltered Cu Kα radiation. The diffuse-reflectance spectra (DRS) were obtained by a UV-visible spectrophotometer (PE Lambda 950) using BaSO₄ as a reference. The photoluminescence (PL) and PL excitation (PLE) spectra of the samples were measured by using an FLS-920T fluorescence spectrophotometer equipped with a 450W Xe light source and double excitation monochromators. The PL decay curves were measured by an FLS-920T fluorescence spectrophotometer with nF900 nanosecond Flashlamp as the light source. The quantum efficiency (QE) was measured by a Fluorlog-3 spectrofluorometer equipped with 450W xenon lamp (Horiba Jobin Yvon). Thermal quenching was tested using a heating apparatus (TAP-02) in combination with PL equipment. All of the measurements were performed at room temperature.

3. Results and discussion

3.1 Phase identification of as-prepared phosphors

Figures 1(a) and 1(b) display the results of Rietveld refinement of the XRD data profiles of SPB host by GSAS program [23] (R_wp = 7.24, χ² = 2.946) and the representative XRD patterns of SPB: 0.03Ce³⁺, SPB: 0.03Ce³⁺, 0.05Mn²⁺ and SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.03Tb³⁺ samples. No detectable impurity phase is observed in the obtained samples even at high doping concentration. The XRD profiles are well fitted with the calculated data according to Chen’s report [24], indicating that the obtained samples are single phase and the rare earth ions have been successfully incorporated in the SPB host lattices without changing the crystal structure.

Fig. 1 (a) The experimental, calculated, and difference results of the XRD refinement of SPB host; (b) The representative XRD patterns of SPB: 0.03Ce³⁺, SPB: 0.03Ce³⁺, 0.05Mn²⁺ and SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.03Tb³⁺ samples. The calculated data of SPB is shown as reference..

Download Full Size | PDF

3.2 Photoluminescence properties of SPB: Ce³⁺ and SPB: Mn²⁺

Figure 2 shows the PL and PLE spectra for SPB: Ce³⁺ (a) and SPB: 0.01Mn²⁺ (b). The PLE spectrum of SPB: Ce³⁺ at 354 nm excitation extends from 240 to 420 nm with two distinct bands peaking at 297 and 354 nm attributed to the 4f–5d transition of Ce³⁺ ions, which indicates that the phosphors can be effectively excited by UV light. The emission spectra show asymmetric broadband characteristic of Ce³⁺ ions, but the FWHM value amounts to 5030 cm⁻¹, which is not comparable to that typically observed for Ce³⁺ activated phosphors containing a single type of luminescent center (~4000cm⁻¹) [25]. Considering that there are two different cationic sites in SPB (as illustrated in Fig. 2(a)), then we take Gaussian fitting algorithm and find that the curve can be well fitted into four emission bands, which centered at 419 and 454 nm, with an energy difference of 1840 cm⁻¹ and the other two bands peaked at 509 and 562 nm with an energy difference of 1850 cm⁻¹, respectively, which is close to the theoretical energy difference value of Ce³⁺ (~2000 cm⁻¹) [26]. So the four peaks can be justifiably assigned to the 5d-4f (²F_5/2, ²F_7/2) emissions of Ce³⁺ ions occupying two Sr sites (Sr_1/2, Sr₃). Due to a slight difference between crystal fields of Sr₁ and Sr₂ sites, the bands are not resolved distinctly. Generally, the bond length (R) of Sr-O affects the crystal field strength (D_q) significantly, i.e., D_q is proportional to 1/R⁵ [27]. So the bands peaking at 419 and 454 nm are assigned to Ce³⁺ ions occupying Sr_1/2 sites due to weak crystal field (average distance Sr_1/2–O≈2.749 Å) and the bands peaking at 509 and 562 nm are attributed to Ce³⁺ ions occupying Sr₃ sites due to strong crystal field (Sr₃–O≈2.635 Å). Meanwhile, the PL intensity is found to increase gradually with increasing Ce³⁺ ions concentration until it reaches concentration quenching when x = 0.03. In Fig. 2(b), the red emission band of 649 nm is attributed to the ⁴T₁→⁶A₁ transition of 3d⁵ level of Mn²⁺ ions and the corresponding PLE spectrum shows typical d-d transitions of Mn²⁺ ions. Based on the observed significant overlap between the PLE spectrum of Mn²⁺ and the PL spectrum of Ce³⁺ ions (inset in Fig. 2(b)), the effective resonance-type energy transfer is expected to take place from Ce³⁺ to Mn²⁺ ions. It can be seen that the Ce³⁺ or Mn²⁺ ions singly doped SPB emits blue or red light, so it is possible to obtain color-tunable white light emission by adjusting the concentration of Ce³⁺ and Mn²⁺ ions in SPB based on the energy transfer.

Fig. 2 PLE and PL spectra of SPB: Ce³⁺ (a) and SPB: Mn²⁺ (b); The inset shows the relationship of the PL intensity of Ce³⁺ with Ce³⁺ doping concentration (in Fig. a) and the overlap between the PL of Ce³⁺ and the PLE of Mn²⁺ (in Fig. b)

Download Full Size | PDF

3.3 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺ and luminescence dynamics

In SPB: 0.03Ce³⁺, xMn²⁺(0.005≤x≤0.05) (Fig. 3(a)), the PL spectra upon Ce³⁺ excitation at 354nm not only exhibit the Ce³⁺ blue emission at 441 nm but also the Mn²⁺ red emission at 649 nm. Meanwhile, as an increase of Mn²⁺ at fixed Ce³⁺ concentration, the intensity of the blue band decreases gradually while the red component increases (see Fig. 3(b)). These results further support the occurrence of energy transfer from Ce³⁺ to Mn²⁺. To further understand the process of energy transfer, the PL decay curves of Ce³⁺ in SPB: 0.03Ce³⁺, xMn²⁺ excited at 354 nm are measured and depicted in Fig. 3(c). The corresponding luminescent decay times can be fitted by a second-order exponential mode and the average decay time τ can be determined by the formula [28]

τ = \frac{A_{1} τ_{1}^{2} + A_{2} τ_{2}^{2}}{A_{1} τ_{1} + A_{2} τ_{2}}

where A₁ and A₂ are constant, τ₁ and τ₂ are the two exponential component of the decay time. The calculated decay times are listed in Fig. 3(c). According to Dexter’s formulation [29], the energy transfer rate is given by

P (R) \propto \frac{Q_{A}}{R^{b} τ_{D}} \int \frac{f_{D} (E) F_{A} (E)}{E^{C}} d E

where τ_D is the decay time of the donor emission, Q_A is the total absorption cross section of the acceptor ion, R is the distance between the donor and the acceptor, and b and c are parameters dependent on the type of energy transfer. The probability functions f_D(E) and F_A(E) represent the observed shapes of the donor emission band and the acceptor absorption band, respectively. Thus, according to Eq. (2), it becomes clear that the energy transfer rate P is in inverse proportion to the decay time τ_D. It can be seen that the decay lifetime of the Ce³⁺ decreases monotonically with an add up of the Mn²⁺ doping concentration, which also supports the energy transfer from the Ce³⁺ to Mn²⁺. Moreover, the energy transfer efficiency η_Ce→Mn can be expressed by [30]

η_{T} = 1 - \frac{τ_{S}}{τ_{S 0}}

Where τ_S is the lifetime of the Ce³⁺ in the absence of the Mn²⁺ and τ_S0 is the lifetime of the Ce³⁺ in the presence of the Mn²⁺. The decay lifetime values are used for calculation, and the results are presented in Fig. 3(d). It can be seen that the energy transfer efficiency η_T is found to increase gradually with the increase of Mn²⁺ content. The critical distance R_c for energy transfer from the Ce³⁺ to Mn²⁺ is calculated using the concentration quenching method. The critical distance was estimated according to the equation [25]

R_{C e - M n} = 2 {[\frac{3 V}{4 π x_{c} N}]}^{1 / 3}

where V is the volume of the unit cell, x_c is the critical concentration, and N is the number of available sites for the dopant in the unit cell. In our case, N is 10, and V is estimated to be 607.29 Å³. The critical concentration (x_c), at which the luminescence intensity of Ce³⁺ is one-half of that in the sample in the absence of Mn²⁺, is 0.09. Therefore, the critical distance (R_c) was calculated to be 10.88 Å. This value is longer than 4 Å, indicating the energy transfer is not via exchange interaction mechanism but electric multipolar interaction [31, 32].

Fig. 3 (a) PL spectra of SPB:0.03Ce³⁺, xMn²⁺; (b) Relative intensity of the blue and red emission bands; (c) Decay curves of Ce³⁺ for SPB:0.03Ce³⁺, xMn²⁺ monitored at 421 nm; (d) The correlation between η_T/τ and x under 354 nm excitation.

Download Full Size | PDF

3.4 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺, Tb³⁺

To enhance the low color rendering property due to a green-region deficiency as seen in Fig. 3(a) and obtain warm white emission, we also prepared SPB: Tb³⁺ and SPB: 0.03Ce³⁺, 0.05Mn²⁺, yTb³⁺ (0.005≤y≤0.03). Figure 4(a) shows the PL spectrum of SPB: Ce³⁺ and the PLE spectrum of Tb³⁺. It can be seen that there nearly no spectral overlap between them, which indicates that there may not exist energy transfer between Ce³⁺ to Tb³⁺. The DRS of the SPB, SPB: 0.03Ce³⁺, 0.05Mn²⁺ and SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.01Tb³⁺ samples are shown in Fig. 4(b). It is clear that the spectrum of the SPB host exhibits a high reflection in the visible range. For SPB: Ce³⁺, Mn²⁺ sample, it displays strong absorption bands between 250 and 450 nm attributed to the 4f→5d electronic transitions of the Ce³⁺ and d-d transitions absorption of Mn²⁺. For Ce³⁺, Mn²⁺ and Tb³⁺ co-doped sample SPB, it also shows a strong absorption band in the wavelength range of 250-450 nm except for the enhanced absorption intensity by f-f transition absorption of Tb³⁺, indicating that the trebly doped phosphor may be suitable for UV LED excitation. The PL spectra of SPB: 0.03Ce³⁺, 0.05Mn²⁺, yTb³⁺ (0.005≤y≤0.03) are illustrated in Fig. 4(c) and the inset indicates the intensity change of different emission bands. Upon 354 nm excitation, the PL spectrum is found to consist of three major emission bands in the entire visible spectral region, one is the blue emission arose from the 5d-4f transitions of Ce³⁺, another is the green emission due to the ⁵D₄ -⁷F_J (J = 3,4,5,6) transitions and the third part is a broad red-emitting band caused by Mn²⁺ d-level spin-forbidden transitions. Along with increasing Tb³⁺ concentration, the PL intensity of Tb³⁺ emission is found to increase, and that of Ce³⁺ emission is observed to decrease. This is because there is competition between absorption of Tb³⁺ and Ce³⁺. Both Ce³⁺ and Tb³⁺ have the same chance to absorb the photons. The intensity depends on the number of emission center. Therefore, the emission intensity of Tb³⁺ will increase and that of Ce3 + will decrease with the increase in the number of Tb³⁺. The emission intensity of Mn²⁺ will have the same tendency as that of Ce³⁺. As a result, the emission intensity of Mn²⁺ also decrease accordingly with Tb³⁺ concentration increasing, which is in good agreement with experimental result as shown in Fig. 4(c).

Fig. 4 (a) PLE spectrum of SPB: Tb³⁺ and PL spectrum of SPB: Ce³⁺; (b) DRS of SPB host, SPB:Ce³⁺, Mn²⁺ and SPB:Ce³⁺, Mn²⁺, Tb³⁺; (c) PL spectra of SPB:0.03Ce³⁺,0.05Mn²⁺, yTb³⁺; (d) Representation of the CIE chromaticity coordinates for SPB:0.03Ce³⁺, xMn²⁺ (point nos. 1-5), SPB:0.03Ce³⁺, 0.05Mn²⁺, yTb³⁺ (point nos. 6-9)

Download Full Size | PDF

The main physicochemical properties of as-synthesized SPB serial phosphors are summarized in Fig. 4(d) and Table 1. The correlated color temperature (CCT) was calculated by using McCamy’s approximate formula [33] and Quantum efficiencies are measured by the integrated sphere method and can be calculated according to the equation

Φ = \frac{E_{c} - (1 - A) \cdot E_{b}}{L_{a} \cdot A}

where E_c is the integrated luminescence of the powder caused by direct excitation, E_b is the integrated luminescence of the powder caused by indirect illumination from the sphere and the term L_a is the integrated excitation profile from an empty integrated sphere (without the sample). A is the powder absorbance, which can be obtained by the following formula

A = \frac{L {}_{0}{(λ)} - L_{i} (λ)}{L_{0}}

where L₀(λ) is the integrated excitation profile when the sample is diffusely illuminated by the integrated sphere’s surface; L_i(λ) is the integrated excitation profile when the sample is directly excited by the incident beam. By using Eqs. (5) and (6), the quantum efficiencies of representative phosphors as well as the commercial phosphors YAG are calculated and shown in Table 1. We can see that the emission color of SPB: 0.03Ce³⁺, xMn²⁺, yTb³⁺ phosphors can be tuned from blue to green or red based on the energy transfer from Ce³⁺ to Mn²⁺ and Ce³⁺ to Tb³⁺, which demonstrates controllable emitting colors as a function of Mn²⁺ and Tb³⁺ contents. Hence, the genial warm white light can be realized with excellent CIE (0.35, 0.32), low CCT (4373K) and high CRI (R_a = 89) by appropriately tuning the ratio of the Mn²⁺ to Tb³⁺ under the radiation of UV light, which is better than that (CIE≈(0.291, 0.300), CCT≈8500K) of a LED based on YAG: Ce³⁺ with blue InGaN chip [34] and suitable for the application of warm white light LED. Depending on all above studies and experiments, it can be concluded that the full-color-emitting and color-tunable phosphor Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂): Ce³⁺, Mn²⁺, Tb³⁺ can serve as a great potential and flexible phosphor for using in warm white-light LED devices.

Table 1. The main physicochemical properties of the synthesized SPB serial phosphors.

View Table

3.5 Thermal quenching properties of SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺

The thermal quenching property is one of the important technological parameters for phosphors used in solid-state lighting for it has considerable influence on the light output and color rendering index. The temperature dependent emission spectra for SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺ under excitation at 352 nm were measured and illustrated in Fig. 5. The inset displays a comparison of the thermal luminescence quenching of our phosphor with that of the commercial yellow phosphor YAG: Ce³⁺ (Mitsubishi Chemical Corporation, Japan). As can be seen in Fig. 5, the thermal stability of SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺ is inferior to that of YAG:Ce³⁺ when the temperature is above 50 °C, though the intensity of both of them dropped to about 63% of its initial value at a temperature of 200 °C. The observation can be rationalized by the fact that increasing temperature has increased the population of higher vibration levels, the density of phonons and the probability of non-radiative transfer (energy migration to defects). For the application in high power LEDs, thermal quenching property has to be enhanced.

Fig. 5 The temperature-dependent emission intensity of the optimized SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺ sample.

Download Full Size | PDF

4. Conclusion

In conclusion, a series of single-phase novel emission tunable Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂): Ce³⁺, Mn²⁺, Tb³⁺ phosphors have been synthesized and the luminescence properties as well as energy transfer from Ce³⁺ to Mn²⁺ and Ce³⁺ to Tb³⁺ are investigated for the first time. The energy transfer efficiency and critical distance R_c are also calculated. The emission color of SPB: 0.03Ce³⁺, xMn²⁺, yTb³⁺ phosphors can be tuned from blue to green or red based on the effective energy transfer. More importantly, the wavelength-tunable warm white light can be realized with a superior CIE (0.35, 0.32), high CRI (R_a = 89) and low CCT (CCT = 4373K). Our results indicate that the full-color-emitting and color-tunable phosphor Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂): Ce³⁺, Mn²⁺, Tb³⁺ can be a promising candidate for single-composition phosphor converted white-emitting LEDs.

Acknowledgments

This work is supported by National Science Foundation for Distinguished Young Scholars (No. 50925206) and Specialized Research Fund for the Doctoral Program of Higher Education (No. 20120211130003).

References and links

1. J. M. Phillips, M. E. Coltrin, M. H. Crawford, A. J. Fischer, M. R. Krames, R. Mueller-Mach, G. O. Mueller, Y. Ohno, L. E. S. Rohwer, J. A. Simmons, and J. Y. Tsao, “Research challenges to ultra-efficient inorganic solid-state lighting,” Laser Photonics Rev. 1(4), 307–333 (2007). [CrossRef]

2. J. H. Ryou and R. D. Dupuis, “Focus issue: Optics in LEDs for lghting,” Opt. Express 19(S4Suppl 4), A897–A899 (2011). [CrossRef] [PubMed]

3. D. Feezell, J. Speck, S. DenBaars, and S. Nakamura, “Semipolar (20⁻2⁻1) InGaN/GaN Light-Emitting Diodes for high-efficiency solid-state lighting,” J. Display Technology 9, 190–198 (2013). [CrossRef]

4. R. Arif, Y. Ee, and N. Tansu, “Polarization engineering via staggered InGaN quantum wells for radiative efficiency enhancement of Light Emitting Diodes,” Appl. Phys. Lett. 91(9), 091110–091112 (2007). [CrossRef]

5. H. Zhao, G. Liu, J. Zhang, R. Arif, and N. Tansu, “Analysis of internal quantum efficiency and current injection efficiency in III-nitride Light-Emitting Diodes,” J. Display Technology 9(4), 212–225 (2013). [CrossRef]

6. S. Choi, M. Ji, J. Kim, H. Kim, M. Satter, P. Yoder, J. Ryou, R. Dupuis, A. Fischer, and F. Ponce, “Efficiency droop due to electron spill-over and limited hole injection in III-nitride visible light-emitting diodes employing lattice-matched InAlN electron blocking layers,” Appl. Phys. Lett. 101(16), 161110 (2012). [CrossRef]

7. G. Liu, J. Zhang, C. Tan, and N. Tansu, “Efficiency-droop suppression by using large-bandgap AlGaInN thin barrier layers in InGaN Quantum-Well Light-Emitting Diodes,” IEEE Photonics J. 5(2), 2201011 (2013). [CrossRef]

8. Y. K. Ee, P. Kumnorkaew, R. A. Arif, H. Tong, H. Zhao, J. F. Gilchrist, and N. Tansu, “Optimization of Light Extraction Efficiency of III-Nitride Light Emitting Diodes with Self-Assembled Colloidal-based Microlenses,” IEEE J. Sel. Top. Quantum Electron. 15(4), 1218–1225 (2009). [CrossRef]

9. J. Jewell, D. Simeonov, S. Huang, Y. Hu, S. Nakamura, J. Speck, and C. Weisbuch, “Double embedded photonic crystals for extraction of guided light in light-emitting diodes,” Appl. Phys. Lett. 100(17), 171105 (2012). [CrossRef]

10. R. J. Xie, N. Hirosaki, M. Mitomo, K. Sakuma, and N. Kiumra, “Wavelength-tunable and thermally stable Li-α-sialon:Eu²⁺ oxynitride phosphors for white light-emitting diodes,” Appl. Phys. Lett. 89(24), 241103 (2006). [CrossRef]

11. J. S. Kim, P. E. Jeon, J. C. Choi, H. L. Park, S. I. Mho, and G. C. Kim, “Warm-white-light emitting diode utilizing a single-phase full-color Ba₃MgSi₂O₈:Eu²⁺, Mn²⁺ phosphor,” Appl. Phys. Lett. 84(15), 2931–2933 (2004). [CrossRef]

12. H. Yamamoto, “White LED phosphors: the next step,” Proc. SPIE 7598, 759808, 759808-10 (2010). [CrossRef]

13. L. Wang, X. Zhang, Z. D. Hao, Y. S. Luo, X. J. Wang, and J. H. Zhang, “Enriching red emission of Y₃Al₅O₁₂: Ce³⁺ by codoping Pr³⁺ and Cr³⁺ for improving color rendering of white LEDs,” Opt. Express 18(24), 25177–25182 (2010). [CrossRef] [PubMed]

14. W. R. Liu, C. C. Lin, Y. C. Chiu, Y. T. Yeh, S. M. Jang, and R. S. Liu, “ZnB₂O₄:Bi³⁺,Eu³⁺:a highly efficient, red-emitting phosphor,” Opt. Express 18(3), 2946–2951 (2010). [CrossRef] [PubMed]

15. Y. Zhang, L. Wu, M. Ji, B. Wang, Y. Kong, and J. Xu, “Structure and photoluminescence properties of KSr₄(BO₃)₃:Eu³⁺ red-emitting phosphor,” Opt. Mater. Express 2(1), 92–102 (2012). [CrossRef]

16. H. C. Kuo, C. W. Hung, H. C. Chen, K. J. Chen, C. H. Wang, C. W. Sher, C. C. Yeh, C. C. Lin, C. H. Chen, and Y. J. Cheng, “Patterned structure of remote phosphor for phosphor-converted white LEDs,” Opt. Express 19(S4Suppl 4), A930–A936 (2011). [CrossRef] [PubMed]

17. C. Huang, T. Chan, W. Liu, D. Wang, Y. Chiu, Y. Yeh, and T. Chen, “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,” J. Mater. Chem. 22(38), 20210–20216 (2012).

18. C. Chang and T. Chen, “White light generation under violet-blue excitation from tunable green-to-red emitting Ca₂MgSi₂O₇: Eu, Mn through energy transfer,” Appl. Phys. Lett. 90(16), 161901 (2007). [CrossRef]

19. S. S. Sanayea and B. S. Dhabekar, “Energy transfer process in CaSO₄: Tb, Ce phosphor,” J. Lumin. 105(1), 1–8 (2003). [CrossRef]

20. C. Chang and T. Chen, “Sr₃B₂O₆: Ce³⁺, Eu²⁺: A potential single-phased white-emitting borate phosphor for ultraviolet light-emitting diodes,” Appl. Phys. Lett. 91(8), 081902–081904 (2007). [CrossRef]

21. Y. Huang, X. Wang, H. S. Lee, E. Cho, K. Jang, and Y. Tao, “Synthesis, vacuum ultraviolet and ultraviolet spectroscopy of Ce³⁺ ion doped olgite Na(Sr, Ba)PO₄,” J. Phys. D Appl. Phys. 40(24), 7821–7825 (2007). [CrossRef]

22. K. Shinde, S. J. Dhoble, H. C. Swart, and K. Park, “Phosphate Phosphors for Solid-State Lighting,” Springer Ser. Mater. Sci. 174, 1–265 (2012). [CrossRef]

23. A. C. Larson and R. B. Von Dreele, “General Structure Analysis System (GSAS) ,” Los Alamos Nat. Lab., Report, LAUR 86–748, 2000.

24. S. Chen, S. Hoffmann, W. Carrillo-Cabrera, L. G. Akselrud, Y. Prots, U. Schwarz, J. T. Zhao, and R. Kniep, “Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂): Growth and crystal structure of a strontium phosphate orthoborate metaborate closely related to the apatite-type crystal structure,” J. Solid State Chem. 183(3), 658–661 (2010). [CrossRef]

25. G. Blasse and A. Bril, “Investigation of Some Ce-Activated Phosphors,” J. Chem. Phys. 47(12), 5139–5145 (1967). [CrossRef]

26. L. G. Van Uitert, “An empirical relation fitting the position in energy of the lower d-band edge for Eu²⁺ or Ce³⁺ in various compounds,” J. Lumin. 29, 1–9 (1984).

27. P. D. Rack and P. H. Holloway, “The structure, device physics, and material properties of thin film electroluminescent displays,” Mater. Sci. Eng. Rep. 21(4), 171–219 (1998). [CrossRef]

28. N. Ruelle, M. P. Thi, and C. Fouassier, “Cathodoluminescent properties and energy transfer in red calcium sulfide phosphors CaS: Eu, Mn,” Jpn. J. Appl. Phys. 31(Part 1, No. 9A), 2786–2790 (1992). [CrossRef]

29. D. J. Dexter, “A Theory of Sensitized Luminescence in Solids,” J. Chem. Phys. 21(5), 836–850 (1953). [CrossRef]

30. P. I. Paulose, G. Jose, V. Thomas, N. V. Unnikrishnan, and M. K. R. Warrier, “Sensitized fluorescence of Ce³⁺/Mn²⁺ system in phosphate glass,” J. Phys. Chem. Solids 64(5), 841–846 (2003). [CrossRef]

31. N. Guo, Y. J. Huang, H. P. You, M. Yang, Y. H. Song, K. Liu, and Y. H. Zheng, “Ca₉Lu(PO₄)₇:Eu²⁺,Mn²⁺: a potential single-phased white-light-emitting phosphor suitable for white-light-emitting diodes,” Inorg. Chem. 49(23), 10907–10913 (2010). [CrossRef] [PubMed]

32. C. H. Huang, T. W. Kuo, and T. M. Chen, “Novel red-emitting phosphor Ca₉Y(PO₄)₇:Ce³⁺,Mn²⁺ with energy transfer for fluorescent lamp application,” ACS Appl. Mater. Interfaces 2(5), 1395–1399 (2010). [CrossRef] [PubMed]

33. C. S. McCamy, “Correlated color temperature as an explicit function of chromaticity coordinates,” Color Res. Appl. 17(2), 142–144 (1992). [CrossRef]

34. C. C. Chiang, M. S. Tsai, and M. H. Hona, “Synthesis and photoluminescent properties of Ce³⁺ doped terbium aluminum garnet phosphors,” J. Alloy. Comp. 431(1-2), 298–302 (2007). [CrossRef]

	Sample Compositions	Color	CIE		CCT (K)	CRI (Ra)	QE (%)
	Sample Compositions	Color	x	y	CCT (K)	CRI (Ra)	QE (%)
A	SPB:Ce³⁺	Blue	0.178	0.176	—	—	80.3
B	SPB:Mn²⁺	Red	0.614	0.382	—	—	22.8
C	SPB:Tb³⁺	Green	0.325	0.532	—	—	62.5
1	x=0.005,y=0	Blue	0.198	0.178	—	—	—
2	x=0.01,y=0	Blue	0.218	0.188	—	—	—
3	x=0.02,y=0	Purplish blue	0.238	0.197	—	—	—
4	x=0.03,y=0	Purplish white	0.258	0.202	—	—	—
5	x=0.05,y=0	Pinkish white	0.302	0.218	—	—	71.9
6	x=0.05,y=0.005	Purplish pink	0.374	0.227	1799	—	—
7	x=0.05,y=0.01	White	0.343	0.262	4597	—	—
8	x=0.05,y=0.02	Warm white	0.354	0.322	4373	89	58.5
9	x=0.05,y=0.03	Warm white	0.364	0.349	4304	87	51.2
	InGaN chips +YAG	Cool White	0.291	0.300	8500K	70-800000	70-90
	Standard white light	White	0.33	0.33	5610	—	—

Full-color emission generation from single phased phosphor Sr₁₀[(PO₄)_5.5(BO₄)_0.5](BO₂): Ce³⁺, Mn²⁺, Tb³⁺ for white light emitting diodes

Abstract

1. Introduction

2. Experimental

2.1 Materials and synthesis

2.2 Measurements and characterization

3. Results and discussion

3.1 Phase identification of as-prepared phosphors

3.2 Photoluminescence properties of SPB: Ce³⁺ and SPB: Mn²⁺

3.3 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺ and luminescence dynamics

3.4 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺, Tb³⁺

3.5 Thermal quenching properties of SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺

4. Conclusion

Acknowledgments

References and links

Cited By

Figures (5)

Tables (1)

Equations (6)

Optical Materials Express

Abstract

1. Introduction

2. Experimental

2.1 Materials and synthesis

2.2 Measurements and characterization

3. Results and discussion

3.1 Phase identification of as-prepared phosphors

3.2 Photoluminescence properties of SPB: Ce3+ and SPB: Mn2+

3.3 Photoluminescence properties of SPB: Ce3+, Mn2+ and luminescence dynamics

3.4 Photoluminescence properties of SPB: Ce3+, Mn2+, Tb3+

3.5 Thermal quenching properties of SPB: 0.03Ce3+, 0.05Mn2+, 0.02Tb3+

4. Conclusion

Acknowledgments

References and links

Cited By

Figures (5)

Tables (1)

Equations (6)

Optical Materials Express

3.2 Photoluminescence properties of SPB: Ce³⁺ and SPB: Mn²⁺

3.3 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺ and luminescence dynamics

3.4 Photoluminescence properties of SPB: Ce³⁺, Mn²⁺, Tb³⁺

3.5 Thermal quenching properties of SPB: 0.03Ce³⁺, 0.05Mn²⁺, 0.02Tb³⁺