Browsing by Author "Chen, Teng Ming"

Now showing 1 - 3 of 3

Analysis of growth kinetics and impact of NH3 on the morphology evolution of hexagonal-prism shaped Y4O(OH)(9)NO3/Y2O3 single crystals
(2017-11-01)
Ray, Sudeshna
;
Nair, Govind B.
;
Dhoble, S. J.
;
Kato, H.
;
Kakihana, Masato
The effect of NH3 on the morphology evolution of single crystalline hexagonal-prism like Y4O(OH)(9)NO3 and Y2O3 has been systematically investigated, as a function of reaction time, by using a combination of powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Rational control over the morphology has been achieved by the choice of suitable electrolytes like NaNO3, KNO3, NH4NO3, KCl and NH4Cl in the presence of NH4OH. We report that the cross-sectional geometry of hydrothermally grown one-dimensional Y4O(OH)(9)NO3 crystals can be tuned from spherical to hexagonal-prism like shape by introducing a particular reagent like NH4NO3 in the presence of NH4OH. An 'oriented attachment' mediated growth process takes place along with the 'dissolution-recrystallization' route which eventually resulted in the generation of the single crystals with hexagonal-prism like morphology. (C) 2017 Elsevier Ltd. All rights reserved.
Enhanced conversion efficiency of crystalline Si solar cells via luminescent down-shifting using Ba2SiO4 : Eu2+ phosphor
(2014-01-01)
Hung, Wen Bin
;
Chen, Juyn Ye
;
Sung, Kien Wen
;
Chen, Teng Ming
;
應用化學系
The colloidal submicron needle-like Ba2SiO4 : Eu2+ phosphor coated on microtextured silicon surface has been used as a luminescent down-shifting (LDS) material for enhancing the power conversion efficiency of solar cells. Under a simulated one-sun illumination, upon phosphor coating the solar cells showed an enhancement of the short-circuit current density (J(sc)) increased from 34.00 to 34.48 mA/cm(2), meanwhile the power conversion efficiency (PCE) was enhanced from 15.13% to 15.36%. The related underlying mechanism for these enhancements can be attributed to photon down-shifting and light scattering effect through the investigation of PLE spectrum, reflectance, and external quantum efficiency. Our results indicate that the colloidal submicron needle-like Ba2SiO4 : Eu2+ phosphor not only act as LDS centers in the UV region but also serve as an antireflection coating for enhancing the light absorption in the visible regime.
Structural and spectroscopic characterizations of a new near-UV-converting cyan-emitting RbBaScSi3O9:Eu2+ phosphor with robust thermal performance
(2017-08-05)
Ray, Sudeshna
;
Tadge, Prachi
;
Dhoble, S. J.
;
Nair, Govind B.
;
Singh, Akash
To facilitate the next generation of White Light Emitting Diodes (WLEDs) with higher color rendering and warm lighting, the development of inorganic phosphor for efficient conversion of photons from blue/near-UV light to other visible wavelengths is essential. In this regard, we demonstrate a systematic, cost effective, solution-processable, easily scalable and fully controllable synthesis of a series of RbBaScSi3O9:xEu(2+) (x = 0.2, 0.5, 2, 5, 7), a new cyan emitting scandium silicate based phosphor with 79% internal quantum efficiency under n-UV excitation with robust thermal performance. The concept as well as the methodology of using a "Mineral Inspired Approach" emerges as a new blueprint for the rational design of novel phosphor for phosphor converted WLEDs. The structural refinement, electronic structural calculation using "Density Functional Theory", characteristic photoluminescence study, lifetime measurement as well as the thermal quenching properties of the phosphor has been investigated in detail. Owing to the highly efficient cyan emission at lambda(max) similar to 492 nm a full-width at half-maximum of 63 cm(-1) that shows only very low thermal quenching (89.28% relative to the PL intensity at 150 degrees C with respect to that of measured at room temperature), reflects the great potential for the industrial application of this particular phosphor. (C) 2017 Elsevier B.V. All rights reserved.