The exploration of stable/efficient phosphor for n -UV chip pumped white light-emitting diodes ( w LEDs) remains an arduous task. Herein, a novel series of color tunable Eu 2+ /Tb 3+ /Sm 3+ tridoped Sc-based cyclosilicate phosphors (KBaScSi 3 O 9 : Eu 2+ /Tb 3+ /Sm 3+ ) have successfully designed and obtained via facile solid-state reaction based on comprehensive consideration of rigidly structural network of host, weak electron-phonon coupling strength and spectral adjustability of codopants via energy transfer (ET). The crystallographic occupancies of Eu, Tb and Sm primary in Ba/K, Ba and Ba sites in the monoclinic host, respectively were determined on the basis of the Rietveld refinements and crystal chemistry rules. The photoluminescence (PL) properties were systematically investigated in conjunction with structural analyses, implying that the ‘warm’ white light with excellent thermal stability is stemmed from combination of optimized blue (Eu 2+ ), green (Tb 3+ ) and red (Sm 3+ ) emissions via Eu → Tb → Sm ET strategy. Interestingly, Tb ions play both roles of green light luminescent center and ET bridge to achieve cascade ET for connecting Eu/Sm ion pairs because of the adverse metal-metal charge transfer (MMCT) effect (Eu 2+ + Sm 3+ → Eu 3+ + Sm 2+ ). Furthermore, the phosphor-converted w LEDs (pc- w LEDs), by encapsulating the optimal KBS: 4 %Eu/4 %Tb/6 %Sm with commercial n -UV LED chip, show high thermal stability with satisfactory electroluminescence (EL) performances. These results indicate the KBS: Eu/Tb/Sm phosphors are potential candidates for application in high power n -UV pumped pc- w LEDs.
Bihao Zhuang,Zicong Jin,Jiahuan Deng,Hui Xiong,Wenzhe Li,Jiandong Fan
Organic-inorganic hybrid metal halide perovskite has played an important role in optoelectronics and photonics due to their extremely high photoluminescence quantum yield (PLQY). However, considering the strong nonmetallic property of antimony (Sb), the excitons in antimony-based single crystals are usually dissipated in the form of non-radiative recombination under organic-inductive effect, which leads to the low PLQY. Herein, two kinds of perovskite-like single crystals, i.e., (8-HQ) 2 SbCl 3 and (8-HQH)SbCl 4 , are innovatively grown. The density functional theory (DFT) calculations reveal that the unique luminescence characteristics are associated with the inductive effect of organic coordination and exciton effect in the metal octahedral skeleton. When Cl − replaces the organic ligand in (8-HQ) 2 SbCl 3 , the inductive effect is reduced while the self-trapped exciton effect in the metal octahedron is enhanced. Besides, the theoretical research on electron transmission in a modeling device reveals that the hydrogen bond of organic A-site in the single crystal promotes the transition of electrons. Based on the luminescent properties of (8-HQH)SbCl 4 , the white LED devices are obtained by coating (8-HQH)SbCl 4 and red phosphor on 450 nm LED chips.
All-inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion-exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO 2 coated Mn 2+ doped CsPbX 3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX 3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well-controlled within 2 nm, which gives the CsPbMnX 3 @SiO 2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr 3 QDs with green emission and CsPbMnX 3 @SiO 2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light-emitting diode (LED) is successfully prepared by the combination of a blue on-chip LED device and the above perovskite mixture. The as-prepared white LED displays a high luminous efficiency of 68.4 lm W −1 and a high color-rendering index of Ra = 91, demonstrating their broad future applications in solid-state lighting fields.
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