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Improved negative thermal quenching effect via high sensitizer doping content in NaGdF4 based active-core/active-shell architecture
摘要： The strategies of introducing interior defects and reducing mean particle size have been applied to improve negative thermal quenching effect (TQE) in Yb3+ sensitized fluoride upconversion (UC) nanocrystals (NCs) recently. Herein, an active-core/active-shell structure with high total Yb3+ doping content is used to enhance the absorption intensity of Er3+ ions. Moreover, the Er3+ activators are doped into the shell to enable the energy migration process from activators to surface defects. In this scenario, with the rise of temperature, the suppression degree of this energy migration process is enlarged followed by an improved negative TQE. Specifically, with rising the temperature from 293 K to 413 K, the integral upconversion emission intensity of 40Yb: NaGdF4@60Yb/2Er: NaGdF4 NCs increases by ~ 8.24 times, while that of NaGdF4@20Yb/2Er: NaGdF4 NCs with a similar mean particle size only enhances ~ 3.44 times.
关键词： Yb3+ concentration,upconversion,temperature sensing,negative thermal quenching
更新于2025-11-14 17:03:37
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A Mn4+-doped oxyfluoride phosphor with remarkable negative thermal quenching and high color stability for warm WLEDs
摘要： Red-emitting phosphors composed of Mn4+-activated fluorides have attracted considerable interest for their applications in warm white light-emitting diodes (WLEDs). However, in addition to moisture instability, the unsatisfactory thermal stability of these phosphors limits their industrial applications. In this study, a novel red phosphor of CsMoO2F3:Mn4+ was synthesized via simple coprecipitation. This red phosphor exhibits an orthorhombic structure with a bandgap of ~3.43 eV. The Mn4+ ions occupy Mo6+ sites at the centers of [MoO2F4]2- octahedrons. This phosphor shows narrow emission around ～633 nm excited by 450 nm blue-chip with high color purity of 99.58%. Satisfactorily, this phosphor exhibits excellent thermal stability and a strong negative-thermal-quenching. The total PL intensity of CsMoO2F3:3.88%Mn4+ phosphor at 275 K strengthens to ~540% relative to that at 25 K, and its relative emission intensity preserves about 129.3% when the temperature rises from room temperature to 423 K (150 ℃). It also shows admirable color stability with a slight chromaticity shift (ΔE) of only ~33.9 × 10?3 in the temperature region from 298 to 473 K. Furthermore, a warm WLED was fabricated by the mixture of red-emitting CsMoO2F3:3.88%Mn4+ and the yellow-emitting YAG:Ce3+ phosphors with a blue-emitting InGaN LED chip. The device exhibits low correlated color temperature (3983 K) and high color-rendering index (Ra = 81.3). With the increasing drive current from 20 mA to 120 mA, the chromaticity coordinate variation (CCV) is only (-0.0163, 0.0202). All these results indicate that the CsMoO2F3:Mn4+ phosphor holds tremendous potential for practical applications in high-power lighting and display with high-performance WLEDs.
关键词： oxyfluoride,red phosphor,luminescence,negative thermal quenching,Mn4+
更新于2025-09-11 14:15:04
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Temperature-dependent photoluminescence processes of GaInP top cell irradiated with 11.5?MeV and 1.0?MeV electrons
摘要： The effects of 11.5 MeV electrons irradiation on the GaInP top cell of GaInP/GaAs/Ge triple-junction solar cells have been investigated by temperature-dependent photoluminescence (PL) measurements. The thermal quenching of PL intensity is observed in the temperature range of 10 K–270 K, attributing to the nonradiative recombination centers H2 (Ev + 0.55 eV) hole trap and H3 (Ev + 0.76 eV) hole trap. A slight negative thermal quenching (NTQ) of PL intensity exists at nearly 300 K and could be associated with the 0.18 eV intermediate states. The temperature-dependent photoluminescence process of GaInP top cell irradiated with 11.5 MeV electrons differs with that irradiated with 1.0 MeV electrons.
关键词： Photoluminescence,Electron irradiation,GaInP top cell,Negative thermal quenching
更新于2025-09-04 15:30:14