Optimal Doping Concentration Research Articles

Effect of Mg2+/Sr2+ addition on luminescence properties of Dy3+ doped glass ceramics containing Ca2Ti2O6

Dy2O3-doped transparent glass-ceramics containing Ca2Ti2O6 crystal phase were synthesized by melting crystallization method. The optimum heat treatment condition was determined to be 710 °C/1.5 h by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmittance curves. The optimal doped concentration of Dy2O3 is 0.4 mol%. The effects of doping with different concentrations of Mg2+ and Sr2+ on the fluorescence intensity of glass-ceramics were discussed. In comparison to Sr2+, the addition of Mg2+ effectively increased the luminescence intensity of 0.4 mol% Dy2O3-doped glass-ceramics. Since Mg2+ has a smaller ionic radius, it has a larger Coulomb potential and is more attractive to O2−, which makes the three-dimensional skeleton of BO6 tilt, and the symmetry of the structure deteriorates, resulting in enhanced luminescence. Comparison of 0.4 mol%Dy2O3-doped glass-ceramic and 8 mol%MgF2-0.4 mol%Dy2O3 co-doped glass-ceramic, the fluorescence intensity increased by 56.8% at 484 nm and 83.5% at 577 nm, the optical band gap value was reduced from 2.7824 eV to 2.4341 eV. The findings suggest that Dy3+-doped glass-ceramics containing Ca2Ti2O6 crystal phase will be used in white light-emitting diodes (W-LEDs).

Numerical Evaluation of Novel Bio‐Photovoltaic Devices Inspired by Photosynthetic Process and High Poly (3,4‐Ethylenedioxythiophene): Poly (styrenesulfonate) Efficacy as Hole Transport Layer

Organic‐based photosystem I (PSI) protein complex bio‐solar cells have appeared as strong candidates for very low‐cost and environmentally friendly photovoltaic devices. The main challenge is their low power conversion efficiency (PCE). Such bottleneck stage in efficiency could be improved from the aspects of the absorber layer and carrier transporting layers. The proposed efficient, eco‐friendly, and simple procedure by applying a uniform pulsed electric field to align PSI dipoles leads to improved significant efficiency. Herein, the experimentally found functional data to benchmark cells have been employed to validate the first PSI numerical model using solar cell capacitance simulator‐1D for the first time. Simulation results show a reasonable agreement with those of experimental. The performance response of the second indium tin oxide/PEDOT: PSS/PSI/Au model is evaluated by varying the physical parameters of the hole transport layer (HTL). PCE characteristic achieved a fourfold increment in the crucial conduction band offset region owing to the reasonable barrier formation of electrons in the HTL/absorber interface. The optimum doping concentration is authorized at a certain μp > 10−2 cm2 V−1 S−1 with an HTL thickness in the order of 102 nm estimating an efficient numerical model compared to the HTL‐free cell.

Multi-site occupancies and dependent photoluminescence of Ca9Mg1.5(PO4)7:Eu2+ phosphors: A bifunctional platform for optical thermometer and plant growth lighting

Herein, we demonstrate an optical thermometer based on single Eu2+ doped Ca9Mg1.5(PO4)7 phosphors, which were prepared by traditional solid-state reaction technique under a reduction atmosphere. Considerations on the bond length obtained by the crystal structure refinement and the dependent photoluminescence performances allow to assign the two distinct emission bands to Eu2+ ions occupied Ca1–Ca3 and Mg2 sites. Moreover, the blue and red emitting bands perfectly match with the photosynthetic action spectrum, which can enhance the indoor plant photosynthesis. The optimal doping content of Eu2+ ions in this Ca9Mg1.5(PO4)7 system is 3 mol%. The corresponding concentration quenching effect is verified as dipole–dipole interaction with the critical distance of 3.315 nm. Furthermore, by exploiting the fluorescence intensity technique, the optical thermal resistance properties of Ca9Mg1.5(PO4)7:Eu2+ are identified based on the temperature dependent emission spectra in a range of 303–523 K. In detail, the maximum absolute and relative sensitivity Sa and Sr of Ca9Mg1.5(PO4)7:Eu2+ thermometer are as high as 0.637%/K and 0.3155 K–1, respectively. Consequently, the Eu2+ doped Ca9Mg1.5(PO4)7 phosphors establish a bifunctional platform for both optical thermometer and plant growth lighting via multi-site occupancies.

Improving the emission intensity and broadening spectrum of borate NaSrBO3 blue phosphor by double ion doping

NaSr1-xCaxBO3:0.01Ce3+ (x = 0.2–0.7) and Na1-yKySr0.69Ca0.3BO3:0.01Ce3+ (y = 0.2–0.6) phosphors was prepared by high-temperature solid-state reaction. The crystal structure, morphology, photoluminescence and quantum yield (QY) were characterized. The emission intensity and QY of the samples were improved by double ion doping. When Ca2+ replaced Sr2+, the emission wavelength was at 416 nm, and the optimal doping concentration was 30 mol %. On this basis, introducing K and adjusting the ratio of Na and K, it turned out that Na1-yKySr0.69Ca0.3BO3:0.01Ce3+ (y = 0.2–0.6) realized spectral broadening and enhanced luminescence. This indicates that the phosphor Na0.6K0.4Sr0.69Ca0.3BO3:Ce3+ are expected to be combined with ultraviolet LED chips for white light lighting.

Manipulating concentration quenching and thermal stability of Eu3+-activated NaYbF4 nanoparticles via phase transition strategy toward diversified applications

Red-emitting phosphors play a vital role in reinforcing the quality of phosphor-converted white light-emitting diodes. Unfortunately, concentration quenching and unsatisfied thermal stability are still the inevitable shortcomings of the red-emitting phosphors. Herein, we utilized phase transition to simultaneously tailor the concentration quenching and thermal stability of Eu3+-activated NaYbF4 (NaYbF4:xEu3+) nanoparticles, in order to overcome these limitations. With the increasing doping level, the resultant samples undergo a phase transition from cubic to hexagonal phase. Notably, the optimal doping content for Eu3+ in the NaYbF4 nanoparticles with cubic phase is 30 mol%. However, when the phase transition occurs, the concentration quenching takes place at a much higher doping concentration, i.e. the optimum content of Eu3+ in the structure is increased to about 80 mol%. Moreover, with elevating the Eu3+ content, the local coordination environment of Eu3+ in the NaYbF4 host lattice is changed from inversion (centrosymmetric) to non-inversion symmetry (non-centrosymmetric), which is further confirmed by the theoretical calculation results via Judd-Oflet theory. Furthermore, compared with cubic samples, the hexagonal NaYbF4:0.8Eu3+ nanoparticles show improved thermal stability. Importantly, utilizing hexagonal NaYbF4:0.8Eu3+ nanoparticles, a designed white light-emitting diode emits warm white light, with desired color coordinates (0.398,0.374), high color rendering index (86.3), and low correlated color temperature (3537 K). Besides, NaYbF4:xEu3+ nanoparticles and their flexible polydimethylsiloxane films exhibit potential applications in high-temperature optical anti-counterfeiting. This work may support a new perspective for tailoring the concentration quenching and thermal stability of various phosphors.

Yb- and Er concentration dependence of the upconversion luminescence of highly doped NaYF4:Yb,Er/NaYF4:Lu core/shell nanocrystals prepared by a water-free synthesis

High sensitizer and activator concentrations have been increasingly examined to improve the performance of multi-color emissive upconversion (UC) nanocrystals (UCNC) like NaYF4:Yb,Er and first strategies were reported to reduce concentration quenching in highly doped UCNC. UC luminescence (UCL) is, however, controlled not only by dopant concentration, yet by an interplay of different parameters including size, crystal and shell quality, and excitation power density (P). Thus, identifying optimum dopant concentrations requires systematic studies of UCNC designed to minimize additional quenching pathways and quantitative spectroscopy. Here, we quantify the dopant concentration dependence of the UCL quantum yield (ΦUC) of solid NaYF4:Yb,Er/NaYF4:Lu upconversion core/shell nanocrystals of varying Yb3+ and Er3+ concentrations (Yb3+ series: 20%–98% Yb3+; 2% Er3+; Er3+ series: 60% Yb3+; 2%–40% Er3+). To circumvent other luminescence quenching processes, an elaborate synthesis yielding OH-free UCNC with record ΦUC of ∼9% and ∼25 nm core particles with a thick surface shell were used. High Yb3+ concentrations barely reduce ΦUC from ∼9% (20% Yb3+) to ∼7% (98% Yb3+) for an Er3+ concentration of 2%, thereby allowing to strongly increase the particle absorption cross section and UCNC brightness. Although an increased Er3+ concentration reduces ΦUC from ∼7% (2% Er3+) to 1% (40%) for 60% Yb3+. Nevertheless, at very high P (> 1 MW/cm2) used for microscopic studies, highly Er3+-doped UCNC display a high brightness because of reduced saturation. These findings underline the importance of synthesis control and will pave the road to many fundamental studies of UC materials.

Power-Dependent Optimal Concentrations of Tm3+ and Yb3+ in Upconversion Nanoparticles.

Lanthanide-doped upconversion nanoparticles (UCNPs) have enabled a broad range of emerging nanophotonics and biophotonics applications. Here, we provide a quantitative guide to the optimum concentrations of Yb3+ sensitizer and Tm3+ emitter ions, highly dependent on the excitation power densities. To achieve this, we fabricate the inert-core@active-shell@inert-shell architecture to sandwich the same volume of the optically active section. Our results show that highly doped UCNPs enable an approximately 18-fold enhancement in brightness over that of conventional ones. Increasing the Tm3+ concentration improves the brightness by 6 times and increases the NIR/blue ratio by 11 times, while the increase of Yb3+ concentration enhances the brightness by 3 times and only slightly affects the NIR/blue ratio. Moreover, the optimal doping concentration of Tm3+ varies from 2% to 16%, which is highly dependent on the excitation power density ranging from 102 to 107 W/cm2. This work provides a guideline for designing bright UCNPs under different excitation conditions.

A novel broadband-excited LaNb2VO9:Sm3+ orange-red-emitting phosphor with zero-thermal-quenching behavior for WLEDs and personal identification

Novel orange-red-emitting LaNb2VO9 (LNV):xSm3+ (x = 0–35 mol%) phosphors were successfully synthesized through the traditional high-temperature solid-state reaction method. The crystal structure, SEM images, particle size distribution, XRD spectra, optimal concentration, zero-thermal-quenching behaviors, and luminescent stability of the samples were exhaustively studied. In particular, the phosphors presented broadband excitation that consisted of O2−→V5+ and O2−→Sm3+ charge transfer bands (CTB). Under 308 nm excitation, LNV:5 mol%Sm3+ phosphor emitted orange-red light with high intensity at the wavelength of 598 nm due to the 4G5/2 → 6H7/2 transition of Sm3+ ions. The sample with the optimal doping concentration of 5 mol% exhibited zero-thermal-quenching. Furthermore, a white light-emitting diode (WLED) with the Commission Internationale de L'Eclairage (CIE) coordinate of (0.347, 0.348) and the superior color rendering index (CRI, Ra) of 90 was smoothly fabricated. With the LNV: 5 mol%Sm3+ phosphor, the level 1–3 structure of latent fingerprints (LFPs) and the detailed features of lip prints were clearly detected under ultraviolet irradiation. Ultimately, the phosphor effectively detected LFPs in various daily life circumstances. Consequently, the zero-thermal-quenching orange-red LNV:Sm3+ phosphors have several promising applications in WLEDs and personal identification.

P‐127: Student Poster: Highly Efficient Green Hyper‐fluorescent Organic Light‐Emitting Diodes using tetradentate Pt(II) Complex as Phosphorescent Sensitizer

We developed green hyper‐fluorescent organic light‐emitting diodes (OLEDs) using tetradentate Pt(II) complex phosphorescent sensitizer to improve external quantum efficiency (EQE) and reduce efficiency roll‐off through suppressed Deter energy transfer to green fluorescent emitter of N9,N9,N10,N10‐tetrakis(4‐(2‐phenylpropan‐2‐yl)phenyl)anthracene‐9,10‐diamine (PhtBuPAD). The tetradentate Pt(II) complex including bulky blocking unit prevented Dexter energy transferred into green fluorescent emitter. In the device evaluation, the hyper‐fluorescent OLED is maintained the high EQE of 21.1% in spite of a high doping concentration of green fluorescent emitter of 3 wt%. As a result, the maximum EQE at optimized doping concentration 2 wt% shows 23.4% and 22.2% at 3000 cd/m2. It induced only 5.0% efficiency roll‐off, which is 6.4‐fold improvement compared to our previous work.

Construction and properties of an osteogenic-antibacterial functionalised drug delivery system based on hydroxyapatite microspheres

Pure hydroxyapatite (HA) has attracted much attention in the field of bone repair materials due to its strong potential for bioavailability, but its low osteogenic activity and non-bacterial inhibition limits its further application in this field. Therefore, in this study, strontium (Sr)-doped hydroxyapatite (HA-Sr) microspheres with a high specific surface area were prepared without adding a templating agent. On this basis, berberine hydrochloride (BBH), a Traditional Chinese antimicrobial agent with excellent antibacterial ability, was loaded to overcome traditional limitations and construct a material with good osteogenic activity and antibacterial capacity. A series of characterization results showed the doping of Sr did not affect the physical phase and morphology of HA but altered its chemical composition and crystallinity, and HA-Sr microspheres had good microscopic morphology and ion retardation, which laid the foundation for the subsequent improvement of the integrated capacity. In vitro cell experiments showed that Sr ions could significantly promote the differentiation of rBMSCs at a range of doping concentrations. In this study, the optimal doping concentration of 3% was systematically screened by cell proliferation assay, alkaline phosphatase staining and alizarin red staining in a small concentration range (1–7%). Subsequently, BBH was loaded with 3% Sr ion-doped HA microspheres to construct the drug loading model. And the sustained release test and antibacterial test further proved that its antibacterial performance was enhanced. The combined results of these experiments indicated that this material was successfully constructed with good osteogenic activity and antibacterial property, and its biological property was greatly improved.

Proton and Oxygen-Ion Conductivities of Hexagonal Perovskite Ba5In2Al2ZrO13.

The hexagonal perovskite Ba5In2Al2ZrO13 and In3+-doped phase Ba5In2.1Al2Zr0.9O12.95 were prepared by the solid-state synthesis method. The introduction of indium in the Zr-sublattice was accompanied by an increase in the unit cell parameters: a = 5.967 Å, c = 24.006 Å vs. a = 5.970 Å, c = 24.011 Å for doped phase (space group of P63/mmc). Both phases were capable of incorporating water from the gas phase. The ability of water incorporation was due to the presence of oxygen deficient blocks in the structure, and due to the introduction of oxygen vacancies during doping. According to thermogravimetric (TG) measurements the compositions of the hydrated samples corresponded to Ba5In2Al2ZrO12.7(OH)0.6 and Ba5In2.1Al2Zr0.9O12.54(OH)0.82. The presence of different types of OH−-groups in the structure, which participate in different hydrogen bonds, was confirmed by infrared (IR) investigations. The measurements of bulk conductivity by the impedance spectroscopy method showed that In3+-doping led to an increase in conductivity by 0.5 order of magnitude in wet air (pH2O = 1.92·10−2 atm); in this case, the activation energies decreased from 0.27 to 0.19 eV. The conductivity−pO2 measurements showed that both the phases were dominant proton conductors at T < 500 °C in wet conditions. The composition Ba5In2.1Al2Zr0.9O12.95 exhibited a proton conductivity ~10−4 S·cm−1 at 500 °C. The analysis of partial (O2−, H+, h•) conductivities of the investigated phases has been carried out. Both phases in dry air (pH2O = 3.5·10−5 atm) showed a mixed (oxygen-ion and hole) type of conductivity. The obtained results indicated that the investigated phases of Ba5In2Al2ZrO13 and Ba5In2.1Al2Zr0.9O12.95 might be promising proton-conducting oxides in the future applications in electrochemical devices, such as solid oxide fuel cells. Further modification of the composition and search for the optimal dopant concentrations can improve the H+-conductivity.

Microstructural, luminescence properties and Judd-Ofelt analysis of Eu3+ activated K2Zr(PO4)2 phosphor for lighting and display applications

A series of light emitting K2Zr(PO4)2 [KZP] phosphors activated with Eu3+ were synthesized through a conventional solid state reaction method. The phase structure, luminescence properties and decay lifetime of the prepared samples were analyzed in detailed. Photo-luminescence (PL) spectra exhibit five emission bands under the excitation at 394 nm. Furthermore, the optimal doping concentration of Eu3+ ion was determined as 2 mol% and the mechanism of energy transfer between two adjacent Eu3+ ions was dominated by the dipole-dipole (d-d) interaction. The Ω2 and Ω4 parameters were estimated for phosphate phosphors using Judd-Ofelt (J-O) theory from the emission spectra. The derived and radiative parameters were also predicted from PL spectra for the prepared phosphors to check their applicability in lasing and photonic applications. The possible lattice sites occupied by Eu3+ ions were investigated using the fitting function type of decay curves. The calculated CIE chromaticity coordinate of KZP: Eu3+ (2 mol%) phosphor verified that its emission light was traced in the pinkish-red zone. Thermally stimulated luminescence (TSL) properties of synthesized samples were also explained in terms of glow curve and kinetic parameters. The aforesaid results revealed that the KZP: Eu3+ phosphors could be potential candidate for solid state lightning and display systems.

Single-Phase Silicate Phosphors (Ba1.3Ca0.7−xSiO4:xDy3+) Doped with Dysprosium for White Solid-State Lighting

Single-phase phosphors have potential advantages such as simple processability, competitive cost, and other optical and optoelectronic properties. Hence, in this study, the silicate phosphors (Ba1.3Ca0.7−xSiO4:xDy3+) doped with Dy3+ ions (x = 0.01–0.05) were synthesized and characterized in detail. X-ray diffraction patterns showed that all the silicate phosphors have a τ-phase hexagonal unit cell independent of doping. However, d-spacing was reduced for the doped samples, indicating that the interplanar interactions were enhanced. Resultantly, the doped phosphors exhibited relatively larger domains with connectivity than the host, although there were sometimes microscale pores. Photoluminescence spectra stipulated that the optimized doping concentration is x = 0.03 for the silicate Ba1.3Ca0.7-xSiO4:xDy3+ phosphors. Finally, the CIE coordinates (0.30, 0.33) confirm that the Dy3+-doped silicate phosphors are well applicable to the white light-emitting diodes for solid-state lighting and display devices.

Optical properties of Sr3WO6:Dy3+ phosphors applying for white LEDs

A series of novel Sr3WO6:xDy3+ (0.01 ≤ x ≤ 0.35) yellow emitting phosphors are synthesized using the conventional high-temperature solid-state method. The phase analysis and optical properties are discussed in detail. Through the X-ray diffraction (XRD) analysis, the obtained phosphors are identified to be pure phases. The Sr3WO6:Dy3+ phosphors emit bright yellow emission light at 578 nm under 352 nm excitation, which is ascribed to the 4F9/2-6H13/2 transitions. The optimum doping concentration is 0.02 mol. The activation energy Ea is calculated to be 0.154 eV. The Commission International de L'Eclairage (CIE) coordinates and correlated color temperature (CCT) of the Sr3WO6:xDy3+ (0.01 ≤ x ≤ 0.35) is located in the yellow region. All results indicate that the Sr3WO6:Dy3+ phosphors have the potential to be applied in the white light-emitting diode (w-LED) field.

Double dielectrics enhancement on the LDMOS using high-k field dielectric and low-k buried dielectric

This paper investigates the double dielectrics enhancement LDMOS (DDE LDMOS) with high-k field dielectric and low-k buried dielectric. The analytical models of the potential and electric field, optimal breakdown voltage and drift doping concentration are established for this novel LDMOS. The validity of the analytical models is confirmed by the simulation results. Based on the analytical and simulated results, the modulation mechanism of the high-k field dielectric and low-k buried dielectric on the electric field and breakdown characteristics of DDE LDMOS are analyzed and compared. Compared to the conventional LDMOS, the specific on-resistance of DDE LDMOS is reduced by 19%, the breakdown voltage and figure of merit (FOM) of the DDE LDMOS can be improved by 62% and 222.4% when the permittivity of high-k field dielectric and low-k buried dielectric are 100 and 2. Meanwhile, the transfer characteristic, output characteristic, frequency characteristic, and switching characteristic of the DDE LDMOS are also discussed.

Self-assembled Zn-functionalized Ni-MOF as an efficient electrode for electrochemical energy storage

Zinc-functionalized nickel metal-organic framework (Zn/Ni-MOF) was grown directly on nickel foam (NF) and used as an efficient binder-free electrode for supercapacitor application. The structural characteristics of the composite materials were analyzed by different analytical techniques. The results obtained revealed flower-decorated ball-shape microstructures were obtained from Zn functionalization of the surface of Ni-MOF microsheets, with a relatively larger surface area and unique pore characteristics. The electrochemical performance measured using a 3 M KOH electrolyte solution indicated that Zn-doped Ni-MOF containing Zn/Ni in the ratio 1:2 (ZNN1) exhibited the optimum performance. ZNN1 revealed good rate capability with a maximum specific capacitance of 391 Fg-1 at a current density of 1 Ag-1 and retained about 70% of its initial capacitance at 10 Ag-1. The electrode also possessed maximum energy and power density of 12 Wh kg−1 and 2000 Wkg-1, respectively, with a high cycling stability of 85% after 5000 cycles. The enhanced electrochemical performance of ZNN1 was attributed to the increase in the surface area and electrical conductivity of Ni-MOF occasioned by incorporation of an optimum concentration of Zn dopant. The charge storage mechanism was predominantly controlled by the diffusion process, which suggests that the method employed in this study is promising for the fabrication of pseudocapacitive materials.

Optimized luminescent intensity of Ca2MgWO6:Er3+,Yb3+ up-conversion phosphors by uniform design and response surface methodology

In this work, an experimental optimization design methodology was used to determine the accurate optimal doping concentrations of a specific multi-doped luminescent material with the strongest expected luminescent intensity. Taking Ca2MgWO6:Er3+,Yb3+ up-conversion phosphors as an example, the global optimization of Er3+ and Yb3+ doping concentrations was carried out through a two-step optimization method combining uniform design and response surface methodology. 5-Level-2-factor central composite design was applied to optimize the levels of factors. Impressively, the significance level of established regression model was fully assessed by analysis of variance and its confidence can reach 95%. In addition, genetic algorithm was exploited to solve this regression equation and the optimal doping concentrations of Er3+ and Yb3+ were successfully determined to be 4.682 mol% and 13.556 mol%, respectively. The optimal sample designed by simulation calculation and the sample obtained by variable-controlling method were elaborated. And their luminescent performances and structures were fully investigated. Compared with the traditional sample, the luminescent intensity of the designed optimal sample is enhanced by 1.34 times, featuring an intensity of 2,184,879 that is very close to the desired theoretical value 2,106,800. All of the results suggest that such an experimental optimization strategy could be a new route to optimize luminescent properties of multi-doped phosphors.

Enhanced in-situ electrosynthesis of hydrogen peroxide on a modified active carbon fiber prepared through response surface methodology

• The preparing condition of g-C 3 N 4 /CNTs/ACF was optimized by response surface methodology. • The introduction of g-C 3 N 4 alleviated adsorption energy of oxygen and coordinated ∗ OOH binding capability. • The defects on CNTs could also reduce the oxygen adsorption energy and CNTs simultaneously increases the conductivity of the electrodes. • An appropriate amount of PTFE constructed a gas–liquid-solid three phase equilibrium, promoting the oxygen diffuse on the carbon fiber surface. • The effects of operating parameters on the production of H 2 O 2 were discussed specifically. Electrosynthesis of hydrogen peroxide (H 2 O 2 ) by two-electron oxygen reduction on the cathode is an attractive green approach for environmental remediation and chemical industries. In this study, an active carbon fiber (ACF) electrode modified with graphite carbon nitride (g-C 3 N 4 ) and carbon nanotubes (CNTs) is fabricated by a wet ultrasonic impregnation-calcination method. The doping content of g-C 3 N 4 , CNTs and polytetrafluoroethylene (PTFE) is optimized by response surface methodology (RSM). With optimum doping content, the H 2 O 2 generation by modified ACF increased several times, indicating the physicochemical and electronic transformation of ACF. The introduction of g-C 3 N 4 modulates the electronic structure of ACF, alleviating the adsorption energy of oxygen and coordinating the ∗ OOH binding capability. Besides reducing the oxygen adsorption energy, CNTs simultaneously improve the conductivity of electrodes. In addition, the addition of an appropriate amount of PTFE constructs a gas–liquid-solid three-phase equilibrium, facilitating oxygen diffusion. The effects of operating parameters on H 2 O 2 generation are also investigated and the optimal performance is achieved at current = 0.2 A, pH = 3, and aeration rate = 0.32 L/min. The modified ACF shows great potential in the practical applications for in-situ H 2 O 2 electro-generation.

Approaching 23% efficient n-type crystalline silicon solar cells with a silicon oxide-based highly transparent passivating contact

The concept of passivating contacts is indispensable for realizing high-efficiency crystalline silicon (c-Si)-based solar cells, and its implementation and integration into production lines has become an essential research subject. A desirable transparent passivating contact should theoretically combine excellent electrical conductivity, distinguished surface passivation and high optical transparency. However, it is challenging to simultaneously achieve the optimization of all three requirements. Here, the application potential of the phosphorous-doped polycrystalline silicon-oxide (n-poly-SiOx) as an efficient hole-selective contact in tunnel oxide passivated contact (TOPCon) solar cells is highlighted. The oxygen content can be regulated by the carbon dioxide (CO2) gas flow during the plasma enhanced chemical vapor deposition (PECVD) process, and the optimal doping concentration is determined. While the wide band gap of n-poly-SiOx enables ideal optical performance, it also ensures excellent passivation and high conductivity, which eventually translates into an optimized short-circuit current density (41.53 mA/cm2), fill factor (79.21%), open-circuit voltage (687.8 mV) and efficiency of 22.62% for the proof-of-concept TOPCon solar cell. Additionally, this contact with the incorporation of oxygen elements can suppress the formation of hydrogen-induced blisters, which critically degrades passivation. Our work highlights a promising strategy to improve the performance of TOPCon solar cells by employing n-poly-SiOx based transparent passivating contact, and its passivation mechanism and working principle are also investigated.

Novel niobates Y3NbO7: Ln3+ (Ln=Pr, Sm) phosphors for warm white LED: Synthesis and luminescent properties

Nowadays, the combination of red, blue and green light is one of the mainstream ways to realize high efficient white LED. In this work, novel niobates Y3NbO7: Ln3+ (Ln = Pr, Sm) phosphors have been successfully synthesized by the conventional high temperature solid-state method. The phase composition, luminescent properties and luminescence decay were investigated in detail. Y3NbO7: Ln3+ (Ln = Pr, Sm) phosphors manifested a bright red or yellowish-red emission band. The optimum doping concentration and critical energy transfer distance of Y3NbO7: Ln3+ (Ln = Pr, Sm) were determined. The concentration quenching mechanism of Y3NbO7: Ln3+ (Ln = Pr, Sm) attributed to the electric dipole-dipole interaction. The Y3NbO7: Ln3+ (Ln = Pr, Sm) phosphors exhibited abnormal thermal quenching phenomenon and the luminescence intensity at 453K remained about 78% and 88% of its values at room temperature for Y3NbO7: Pr3+ and Y3NbO7: Sm3+ respectively. All results indicated that Y3NbO7: Ln3+ (Ln = Pr, Sm) as a red or yellowish-red phosphor-converted component could be potentially applied in warm white LED.