Double Perovskite Phosphors Research Articles

The synthesis of lead-free double perovskite Cs2Ag0.4Na0.6InCl6 phosphor with improved optical properties via ion doping

Lead-free double perovskite (DP) phosphors with nontoxicity and excellent moisture, light, and heat stability are promising alternatives to lead halide perovskites for wide uses in optoelectronic applications. As known, their photoluminescence (PL) quantum yield (PLQY) is low in normal. Here, the optical properties of orange-emitting Cs2Ag0.4Na0.6InCl6 DP via doping Bi3+, Sm3+, or Mn2+ ions in the host lattices are proposed and remarkably enhanced. For the Bi3+-doping, the optical band gap of the Cs2Ag0.4Na0.6In1−xBixCl6 DP could be tuned from 3.82 to 2.74 eV and the optimized sample shows a markedly high PLQY of 97.33%. Sm3+-doped Cs2Ag0.4Na0.6InCl6 microcrystals (MCs) are endowed with broad emission derived from self-trapped excitons (STEs) of host. The orange-red emissions at 570, 608, and 655 nm from the transitions of 4G5/2 to 6HJ (J = 5/2, 7/2, and 9/2) of Sm3+, are demonstrated the first observation of PL from the Sm3+-doped lead-free halide DP. The Mn2+-doped Cs2Ag0.4Na0.6InCl6 MCs show dual emission peaks centered at 538 nm and 618 nm, owing to the STEs emission of Cs2Ag0.4Na0.6InCl6 host and 4T1 → 6A1 transition of Mn2+, respectively. It is interesting that the PLQY of Cs2Ag0.4Na0.6InCl6 MCs is dramatically enhanced from 21% to 41% via doping Mn2+.

Fabrication and photoluminescence characteristics of novel red-emitting Ba2LuNbO6:Eu3+ double-perovskite phosphors on near UV WLEDs

Red emitting phosphors play a significant role in accelerating the improvement of illumination quality for white light emitting diodes (WLEDs). In this work, by using solid-state reaction method, an efficient novel Ba2LuNbO6:Eu3+ phosphor with double-perovskite structure was successfully prepared. Here, a series of Ba2LuNbO6:Eu3+ red phosphors can be efficiently pumped by the near-ultraviolet (UV) light and then present high-brightness at orange emission (598 nm, 5D0→7F1) and red emission (610 nm, 5D0→7F2). The ratio values of 610 to 598 nm in Ba2LuNbO6:Eu3+ phosphors exceed 1 when the content of Eu3+ is larger than 0.4 mol, because the occupation of Eu3+ ions is changed from Lu3+ ions with symmetric sites to Ba2+ ions with asymmetric sites. Besides, the optimized concentration of Eu3+ at the 5D0→7F2 transitions is obtained when x = 1, indicating that there is non-concentration quenching in Ba2LuNbO6:Eu3+ phosphors. Moreover, the CIE chromaticity coordinates of Ba2LuNbO6:Eu3+ was calculated to be (0.587, 0.361), the color purity was calculated to be 72.26% and internal quenching efficiency (IQE) was measured to be 67%. Finally, the thermal stability of Ba2LuNbO6:Eu3+ phosphors was also studied. Our work demonstrates that the novel double-perovskite red-emitting Ba2LuNbO6:Eu3+ phosphors are prospective red emitting elements for WLEDs applications.

Deep‐red‐emitting SrLaLiTeO6: Mn4+ double perovskites: Correlation between Mn4+‐O2− bonding and photoluminescence

AbstractMn4+‐activated deep red‐emitting SrLaLiTeO6 phosphors are investigated for indoor plant growth LED applications for the first time. The phosphors crystallize in monoclinic (P21/n) symmetry is isostructural with SrLaLiTeO6 host. B‐site substitution of Mn4+ ions is confirmed from the redshift of high energy phonon modes in both Raman and IR spectra. The phosphor exhibited a far‐red emission centered at 696 nm corresponding to the 2Eg → 4A2g spin‐forbidden transition of the Mn4+ ions. Approximate crystal field parameters depict the weak influence of neighboring ligand fields on Mn4+ ions and the least covalence of Mn4+‐ligand bonding compared to other double perovskite phosphors. Moreover, the phosphors exhibit excellent thermal stability with an activation energy of 0.23 eV. Phosphor parameters including CCT, color purity, and quantum yield are evaluated and their values meet the requirements of a red‐emitting phosphor for LED applications. Furthermore, the PL emission spectrum of SrLaLiTeO6: Mn4+ matches with the absorption spectrum of plant phytochromes denoting the prospects of this phosphor for indoor plant growth LED applications.

Color tunable Bi3+/Eu3+ co-doped La2ZnTiO6 double perovskite phosphor for dual-mode ratiometric optical thermometry

Rigorous temperature measurement employed to characterize physic-chemical state has compelled scientists to explore more novel materials for contactless optical thermometry, which must overcome the drawbacks of low sensitivity and poor signal discriminability. Here, a novel dual-mode optical thermometer La2ZnTiO6: Bi3+/Eu3+ is designed, prepared and characterized via XRD, XPS, EPR, SEM, EDS, PL spectra and decay time. Under 350 nm excitation, the energy transfer process from Bi3+ to Eu3+ allows the samples to demonstrate adjustable multi-color emissions. The temperature-dependent emission spectra display that the luminescence intensity of Bi3+ ions decreases quite faster than that of Eu3+ ions with temperature, leading to a significant chromaticity shift (∆E = 224 ×10−3 in 293–473 K) visible to naked eyes. Based on fluorescence intensity ratio of Eu3+ versus Bi3+ (FIR = IEu/IBi), the sample shows the maximum relative sensitivity (Sr) of ~1.50% K−1 at 293 K and excellent signal discriminability. Meanwhile, the 5D0→7F2 transition of Eu3+ ions shows a thermal-responsive lifetime with the optimal Sr of 1.23% K−1 at 573 K. This work suggests that the La2ZnTiO6: Bi3+/Eu3+ double perovskite phosphor has a great potential for dual-mode optical thermometry, being beneficial to obtain precise, sensitive and reliable temperature detection.

Single phase multi color emitting Ca2LuTaO6: Dy3+/Eu3+ double perovskite oxide phosphors

AbstractThe trivalent rare‐earth (RE3+) doped phosphors show tremendous achievement in narrow band multicolor line emission for various applications. However, the 4f–4f absorption transition of these ions is forbidden in UV and blue light excitation. Usually, a sensitizer having spin allowed transition was used as a co‐dopant to excite these ions via the energy transfer phenomenon. Another approach promisingly using to excite these ions by efficient energy transfer from the intrinsic emission of the Ca2LuTaO6 double perovskite phosphors host lattice. Phosphors of Ca2LuTaO6 with double perovskite structure were synthesized by using a high‐temperature solid‐state reaction method. The produced Ca2LuTaO6 double perovskite phosphors show an intrinsic broad band emission centered at 424 nm under the excitation of 313 nm UV light. The origin of this broad band blue emission was deeply investigated by using computation and experimental approaches. The trivalent activator Dy3+ and Eu3+ were doped is a single and co‐dopant in the produced Ca2LuTaO6 phosphors to check their excitation in UV and near‐UV spectral region. X‐ray diffraction and scanning electron microscopy were used to investigate the structure and phase analysis. Various characterizations such as photoluminescence excitation, emission, and CIE chromaticity coordinates were measured which illustrate the potential of Dy3+ and Eu3+ activated Ca2LuTaO6 double perovskite phosphors for narrow band multicolor line emission for various applications.

Photoluminescence and optical temperature measurement of Mn4+/Er3+ co-activated double perovskite phosphor through site-advantageous occupation

Because traditional methods based on thermal coupling energy level temperature measurement have large errors, a new temperature sensing strategy is proposed to attain strong sensitivity and excellent signal resolution ability. The rare-earth and also transition metal ions with poles apart thermal quenching channels are used as dual emission centers to find a suitable host to achieve high-efficiency dual-mode emission. In this work, a string of phosphors with NaLaMgWO6 (NLMW) as the host, the single-doped and double-doped Mn4+ and Er3+ phosphors were adopted by the traditional high temperature solid-state reaction method. The crystallographic structure of the phosphor was analyzed by X-ray power diffraction and Rietveld refinement methods, and the results showed that a pure double perovskite phosphor with a monoclinic structure was successfully prepared. The photoluminescence excitation and emission spectrum properties, CIE chromaticity coordinates and photoluminescence spectra at different temperatures are detailed studied. Excited by ultraviolet light (300 nm), corresponding to the 4A2→4T1 transition of Mn4+ and the charge transfer from O2– to W6+ of Er3+. There is no energy transfer between Mn4+ and Er3+. NLMW:Mn4+/Er3+ phosphors were especially sensitive to temperature changes within the scope of 303 K to 523 K. As the temperature increases, the fluorescence intensity of Mn4+ is thermally quenched faster than Er3+. The luminescent intensity ratio of Er3+ thermal coupling level and the FIR of Er3+/Mn4+ are used to study the temperature performance. The results show that the maximum relative sensitivity of FIR up to 1.31% K−1, which is higher than the maximum temperature sensitivity based on the thermal coupling energy level, and which is beyond most of the non-contact temperature measurement materials previously reported, confirming that NLMW:Mn4+/Er3+ phosphors have application potential in non-contact temperature measurement.

Enhanced luminescence performances of Sr2YTaO6:Mn4+ narrow red phosphor by Rn+ (Li+,Na+,Ca2+,Mg2+) ions

Mn4+ doped oxides as red phosphor have attracted much attention for achieving the white light-emitting-diodes (LEDs) and potential application in plant cultivation LEDs. In the present work, Mn4+ doped double perovskite Sr2YTaO6 phosphor were synthesized using solid-state reaction and XRD patterns for the representative samples revealed its single phase structure. The optical band gaps of Sr2YTaO6 calculated by the diffuse reflectance spectra (3.93 eV) and density functional theory (3.86 eV) were in very good agreement. The photoluminescence excitation spectrum of Sr2YTaO6:0.6%Mn4+ showed two broad bands whose peaks at 415 and 502 nm. The red emission band centered at 683 nm was originated from 2Eg → 4A2g transition of Mn4+, which matched well with the absorption spectrum of the phytochrome PFR, demonstrating the Sr2YTaO6:0.6%Mn4+ phosphors can be used as the indoor plant growth lighting. The temperature dependent luminescence also analyzed, indicating its good thermal stability. Impressively, Li+/Na+/Mg2+/Ca2+ dopants play an important role in enhancing luminous intensity of Sr2YTaO6:Mn4+ and the mechanisms were systematically studied.

Dual emission and energy transfer of Bi3+ and Mn4+ in double perovskite CaLaMgTaO6 phosphors for white light-emitting diodes

Dual emission and energy transfer of Bi3+ and Mn4+ in double perovskite CaLaMgTaO6 phosphors for white light-emitting diodes

Synthesis, crystal structure and photoluminescence properties of novel far-red-emitting SrLaZnSbO6:Mn4+ double-perovskite phosphors for plant cultivation LEDs

In this work, we demonstrated novel Mn4+-activated double-perovskite SrLaZnSbO6 (SLZS) far-red-emitting phosphors for plant cultivation LED lighting. These SLZS:Mn4+ far-red-emitting phosphors doped with various Mn4+ concentrations were successfully prepared by using a traditional high-temperature solid-state reaction route. The phase purity, crystal structure, photoluminescence properties, decay lifetimes, CIE chromaticity coordinates and temperature-dependent spectra of as-prepared samples were systematically studied. The SLZS:Mn4+ phosphors showed an intense far-red emission band in the 650−800 nm spectral region with a maximum at 706 nm under 364 nm excitation, which was due to the 2Eg→4A2g transition of Mn4+ ions. The optimal doping concentration of Mn4+ ions in SLZS:Mn4+ phosphors was found to be 0.5 mol%. And the CIE chromaticity coordinates of SLZS:0.5 %Mn4+ phosphors were calculated to be (0.7276, 0.2724), which were located in the far-red region. The emission spectrum of SLZS:Mn4+ phosphors could match well with the absorption band of phytochrome PFR. All of these results demonstrate that SLZS:Mn4+ phosphors have a huge potential application in indoor plant cultivation.

Bright red luminescence from Mn4+ ions doped Sr2LuTaO6 double-perovskite phosphors

This paper reported on the synthesis, crystal structure and photoluminescence properties of novel deep-red emitting Mn4+ ions doped Sr2LuTaO6 (SLT) double-perovskite phosphors. The SLT:Mn4+ red phosphors were successfully synthesized by high-temperature solid-state route under air atmosphere. The phase purity and crystal structure of these as-prepared SLT:Mn4+ red phosphors were analyzed by X-ray diffraction (XRD) patterns and XRD Rietveld refinement. The luminescence properties including excitation and emission spectra, luminescence decay lifetimes, the Commission International De IʼEclairage (CIE) chromaticity coordinates, temperature-dependent photoluminescence spectra, and internal quantum efficiency were investigated in detail. It was found that under 346 nm excitation, the SLT:Mn4+ phosphors exhibited bright red emissions around 686 nm in the 630–750 nm wavelength range. Besides, Mn4+ concentration dependent luminescence properties were also analyzed, and the optimal doping concentration of Mn4+ ions was found to be 0.4%. More importantly, the CIE chromaticity coordinates of SLT:0.4%Mn4+ sample were determined to be (0.7286, 0.2714), and its internal quantum efficiency was measured as 37%.

Structure and photoluminescence of Eu3+ doped Sr2InTaO6 red phosphor with high color purity.

The Eu3+-doped Sr2InTaO6 phosphors were obtained by solid-state reaction method and the phase purity of Sr2InTaO6:Eu3+ samples were investigated by the XRD patterns. The Rietveld refinements were conducted to further obtain crystal structure information and the results indicate Sr2InTaO6:Eu3+ samples crystallized in the monoclinic system with a P121 space group. The optical band gap of Sr2InTaO6 was calculated to be 3.84 eV by the diffuse reflectance spectra, which are consistent with the result (3.823 eV) of density functional theory. Under 396 nm excitation, the Sr2InTaO6:Eu3+ phosphor showed a red photoluminescence band centered at about 624 nm due to the 5D0 → 7F2 transition. Monitored at 624 nm, the phosphors showed two wide bands from 200 nm to 500 nm, which originated from the charge-transfer band of Eu3+–O2− and f–f transitions of Eu3+ ions. The optimum luminous concentration is 0.12 because of the concentration quenching determined to be a quadrupole–quadrupole interaction. The luminescence decay lifetimes of the Sr2InTaO6:Eu3+ phosphors were milliseconds. Significantly, the temperature-dependent emission spectra of Sr2InTaO6:0.12Eu3+ phosphors exhibited good thermal stability and the CIE chromaticity coordinates of Sr2InTaO6:0.12Eu3+ were (0.6265, 0.3693) with high color purity. The present work demonstrated that the Sr2InTaO6:Eu3+ red-emitting phosphors show great application in lighting technology.

High-brightness red-emitting double-perovskite phosphor Sr2LaTaO6:Eu3+ with high color purity and thermal stability [Invited

Bright Eu3+-activated double-perovskite Sr2LaTaO6 red-emitting phosphors were successfully synthesized by a high-temperature solid-state method. Under near-ultraviolet excitation at 394 nm, optimal Sr2LaTaO6:0.2Eu3+ phosphors emitted high-brightness red light around 613 nm with the International Commission on Illumination chromaticity coordinates (0.650, 0.349). Notably, the color purity can reach 92%. Impressively, the favorable thermal stability of the Sr2LaTaO6:0.2Eu3+ phosphors was characterized by temperature-dependent emission spectra at different temperatures from 303 to 463 K, and the emission intensity at 423 K remained 73% of its value at 303 K. All of the results suggested that the as-prepared Sr2LaTaO6:0.2Eu3+ phosphors can be used in near-ultraviolet-excitable white light-emitting diodes as a red-emitting color converter.

Constructing ultra-sensitive dual-mode optical thermometers: Utilizing FIR of Mn4+/Eu3+ and lifetime of Mn4+ based on double perovskite tellurite phosphor.

A strategy of optical temperature sensing was developed by using various thermal quenching of Mn4+ and Eu3+ for double perovskite tellurite phosphor in optical thermometers. Herein, SrGdLiTeO6 (SGLT): Mn4+,Eu3+ phosphors were synthesized by a high-temperature solid-state reaction method. The temperature-dependent emission spectra indicated that two distinguishable emission peaks originated from Eu3+ and Mn4+ exhibited significantly diverse temperature responses. Therefore, optical thermometers with a dual-mode mechanism were designed by employing a fluorescence intensity ratio (FIR) of Mn4+ (2Eg→4A2g) and Eu3+ (5D0→7F1,2) and the decay lifetime of Mn4+ as the temperature readouts. The temperature sensing of the phosphors ranging from 300 to 550 K were studied. The maximum relative sensitivities (Sr) are obtained as 4.9% K-1 at 550 K. Meanwhile, the 695 nm emission of Mn4+ possessed a temperature-dependent decay lifetime with Sr of 0.229% K-1 at 573 K. Relevant results demonstrate the SrGdLiTeO6:Mn4+, Eu3+ phosphor as an optical thermometer candidate and also provide constructive suggestions and guidance for constructing high-sensitivity dual-mode optical thermometers.

Crucial processes for upconversion white emission and ultrahigh sensitivity in Er3+/Tm3+/Yb3+ tri-doped double perovskite Gd2ZnTiO6 phosphors

Upconversion (UC) luminescence properties are of great significance in realizing good performances on practical display and sensing applications and that can be tuned by adjusting UC energy transfer (ET) processes. In this work, we devoted to gaining UC white emission and achieving high sensing sensitivity by manipulating ET processes in the Er3+/Tm3+/Yb3+ tri-doped double perovskite Gd2ZnTiO6 (GZT) phosphors. Nearly standard UC white emission with the CIE coordinate of (0.333, 0.331) was obtained based on effective ET processes between Er3+, Tm3+ and Yb3+ in the GZT: 0.5%Er3+/3.5%Tm3+/15%Yb3+ sample. The maximum absolute sensitivity of 5.02 K-1 (473 K) of non-thermally coupled levels (I635−685∕I500−540) and another the maximum absolute sensitivity of 84.6 × 10−4 K−1 (473 K) of thermally coupled levels (I500−540∕I540−600) were gained. The two absolute sensitivities both are higher than that in Tm3+/Yb3+ and Er3+/Yb3+ co-doped double perovskite GZT phosphors, respectively. The enhancements of sensitivities are due to the effective ET processes between Er3+, Tm3+ and Yb3+. This work reveals not only certified UC processes for UC white emission but also a valid idea on the manipulation of UC processes towards high absolute sensitivity in phosphors.

Rb3InCl6: A Monoclinic Double Perovskite Derivative with Bright Sb3+-Activated Photoluminescence.

Here, we present the synthesis and crystal structure of Rb3InCl6 prepared from air stable reagents via a two-step process that proceeds through the intermediate Rb2InCl5·H2O. Rb3InCl6 crystallizes with the Rb3YCl6 structure type (C2/c), which can be derived from the double perovskite structure by noncooperative tilting of isolated [InCl6]3- octahedra. Despite this lowering of symmetry, the optical properties are similar to the cubic double perovskite Cs2NaInCl6. Partial substitution of In3+ with Sb3+ in Rb3InCl6 results in intense cyan-green photoluminescence originating from localized 5s2 to 5s15p1 electronic transitions of [SbCl6]3- polyatomic anions. In comparison with the cubic double perovskite phosphor Cs2NaInCl6:Sb3+, the octahedral tilting distortion increases the electronic isolation of the In/Sb-centered octahedra thus facilitating electron and hole localization on Sb3+ sites, leading to bright photoluminescence. The distorted crystal structure also leads to a larger Stokes shift (1.29 eV) and a corresponding red shift of the emission peak (λmax = 522 nm) compared to the more symmetric Cs2NaInCl6:Sb3+ (Stokes shift ≈ 0.94 eV, λmax = 445 nm).

A novel efficient Mn4+-activated Ba2YTaO6 far-red emitting phosphor for plant cultivation LEDs: Preparation and photoluminescence properties

Novel efficient Ba2YTaO6:Mn4+ (BYT:Mn4+) far-red emitting double-perovskite phosphors for plant cultivation LEDs were reported in this article. These phosphors were successfully synthesized via a traditional high-temperature solid-state reaction method, and their crystal structure, luminescence properties, fluorescence decay lifetimes, Commission Internationale de l'Eclairage (CIE) chromaticity coordinates, internal quantum efficiency, and thermal stability have been systematically investigated. XRD Rietveld refinement demonstrated that the BYT:Mn4+ compound crystallized into cubic crystal system with Fm3‾m space group, and the lattice parameter were a = b = c = 8.445 (7) Å, α = β = γ = 90°, and V = 602.231 (10) Å3. Interestingly, the obtained samples showed an intense far-red emission band centered at 690 nm under excitation of 360 nm, which matched well with the absorption band of phytochrome PFR. In BYT:Mn4+ phosphors, the Mn4+ ions occupied the TaO6 octahedron by replacing the Ta5+ site, and the optimal doping concentration of Mn4+ ions was determined to be 0.4 mol%. The CIE chromaticity coordinates and internal quantum efficiency of BYT:0.4%Mn4+ phosphors were (0.7283, 0.2717) and 41.5%, respectively. In addition, when the temperature reached at 423 K, the emission intensity of BYT:0.4%Mn4+ phosphors remained 37% of that at 303 K. Therefore, all of these investigations demonstrated that BYT:Mn4+ phosphors could be used as potential far-red emitting phosphors for plants cultivation LEDs.

Highly Efficient Lead-Free (Bi,Ce)-Codoped Cs2Ag0.4Na0.6InCl6 Double Perovskites for White Light-Emitting Diodes

Lead-free double perovskite phosphors are promising alternatives to lead halide perovskites for wide uses in optoelectronic applications, but suffer from a low quantum efficiency. Here, we propose ...

Preparation, crystal structure, and photoluminescence properties of high-brightness red-emitting Ca2LuNbO6:Eu3+ double-perovskite phosphors for high-CRI warm-white LEDs

Near-ultraviolet-excited efficient red phosphors are important for fabricating warm-white light-emitting diodes (LEDs) with high color rendering index. Herein, we demonstrated the preparation of novel highly efficient Eu3+ ions-activated Ca2LuNbO6 (CLN) double-perovskite phosphors. These phosphors were prepared by the high-temperature solid-state reaction method and they were characterized by powder X-ray diffraction, Rietveld refinement, excitation and emission spectra, decay lifetimes, internal quantum efficiency, and temperature-dependent emission spectra. The as-prepared phosphors can be efficiently excited by 396 nm near-ultraviolet light and generated bright red luminescence around 591, 616, 656 and 703 nm corresponding to the 5D0→7FJ (J = 1–4) transitions of Eu3+ ions. The optimal doping concentration of CLN:xEu3+ (x = 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8) phosphors was x = 0.4, and the optimal CLN:0.4Eu3+ sample exhibited high-color-purity (96.4%) red emission with internal quantum efficiency as great as 66%. The thermal-quenching resistance was evaluated by measuring their temperature-dependent emission intensities, while the emission intensity at 150 °C was about 65% of that at room temperature. Finally, a warm white LED lamp was made by using a 395 nm LED chip together with a phosphor blend of commercial blue phosphor BaMgAl10O17:Eu2+ and commercial green phosphor (Ba,Sr)2SiO4:Eu2+ and newly developed red phosphor CLN:0.4Eu3+, which gave bright high-quality white light with Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of (0.3878, 0.3725), a correlated color temperature of 3769 K, and a color rendering index of 94 when the driven current was 20 mA. These investigation results clearly revealed the promising application potential of CLN:Eu3+ red phosphors in high-color-quality solid-state white lighting.

Enhanced Eu3+ emission in Ca2LaTaO6:Eu3+ phosphors by codoping Bi3+

The Bi3+/Eu3+ singly and codoped double perovskite Ca2LaTaO6 phosphors were made via solid-phase sintering with the addition of H3BO3. X-ray powder diffraction patterns, morphology, particle size, and photoluminescence properties of them were researched. All of Bi3+/Eu3+ singly and codoped Ca2LaTaO6 phosphors have the same phase with pure Ca2LaTaO6. And all of phosphors have similar morphology and particle size. Exciting at 275 nm, Ca2La1−xEuxTaO6 (x = 0.1, 0.2, 0.3, 0.4, and 0.5) phosphors exhibit bands resulting from 5D0 → 7FJ (J = 0, 1, 2, 3, and 4) transitions of Eu3+. It is found that the critical doping concentration of Eu3+ in Ca2LaTaO6 is about 0.4. Exciting at 272 nm, Ca2La1−yBiyTaO6 (y = 0.05, 0.1, and 0.15) phosphors exhibit emission bands corresponding to the 3P1 → 1S0 transition of Bi3+. There is the occurrence of energy transfer in Bi3+/Eu3+ codoped Ca2LaTaO6 phosphors, which benefits to the enhancement of Eu3+ emission intensity.

Novel efficient deep-red-emitting Ca2LuTaO6:Mn4+ double-perovskite phosphors for plant growth LEDs

Deep-red-emitting phosphors are important for fabricating light-emitting diodes (LEDs) toward applications in plant growth lighting. Herein, we reported on novel efficient deep-red-emitting Mn4+-activated Ca2LuTaO6 (CLT) double-perovskite phosphors. A series of CLT:xMn4+ (x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) samples were prepared by the conventional high-temperature solid-state reaction technique, and they were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), elemental mapping, photoluminescence excitation and emission, decay curves, CIE chromaticity coordinates, internal quantum efficiency (IQE), and temperature-dependent emission spectra. The CLT host crystallized in a monoclinic structure with space group of P21/n, and it contained an octahedral site of TaO6 for Mn4+ doping. Impressively, under 351 ultraviolet light excitation these CLT:xMn4+ phosphors exhibited bright deep-red emissions around 682 nm with CIE chromaticity coordinates of (0.7272, 0.2728) and full width at half maximum (FWHM) of 25 nm. Notably, the optimal CLT:0.2%Mn4+ sample possessed an IQE of 37% and good resistance to thermal quenching (I423 K/I303K = 47%). Considering the emission spectrum of CLT:0.2%Mn4+ deep-red-emitting phosphors matched well with the absorption spectrum of phytochrome PFR, the as-prepared CLT:0.2%Mn4+ phosphors showed great potential in plant growth LEDs.