Temperature Dependent Vibronic Structures in the Emission Spectra of Poly( p -Phenylene Vinylene)

Temperature-dependent photoluminescence (PL) spectroscopy is carried out to probe radiative recombination and related light emission processes in two-dimensional periodic close-packed nanopore arrays in gallium nitride (np-GaN). The arrays were produced by nonlithographic nanopatterning of wurtzite GaN followed by a dry etching. The results of Raman spectroscopy point to a small relaxation of the compressive stress of ~0.24 GPa in nanoporous vs. bulk GaN. At ~300 K, the PL emission is induced by excitons and not free-carrier interband radiative recombinations. An evolution of the emission spectra with T is confirmed to be mainly a result of a decay of nonexcitonic PL emission and less of spectral shifts of the underlying PL bands. A switching of excitonic PL regime observed experimentally was analyzed within the exciton recombination-generation framework. The study provides new insights into the behaviors and physical mechanisms regulating light emission processes in np-GaN, critical to the development of nano-opto-electronic devices based on mesoscopic GaN.

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Photo and Electroluminescent Properties of a Porphyrin-Poly(p-Phenylene Vinylene) Derivative

MRS Proceedings ◽

10.1557/proc-598-bb3.57 ◽

1999 ◽

Vol 598 ◽

Author(s):

J. Morgado ◽

R. Iqbal ◽

G. Yahioglu ◽

L. R. Milgrom ◽

S. C. Moratti ◽

...

Keyword(s):

Energy Transfer ◽

Solid State ◽

Emission Spectra ◽

Luminescent Properties ◽

Phenylene Vinylene ◽

Efficient Energy Transfer ◽

Light Emitting ◽

Efficient Energy ◽

Small Absorption ◽

Pl Emission

ABSTRACTThe solid state luminescent properties of new statistical copolymers of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene and a porphyrin-substituted phenylene vinylene are reported. The photoluminescence, PL, emission shows an efficient energy transfer to the porphyrin, in spite of the small absorption coefficient of the porphyrin in the wavelength range of the poly [2-methoxy-5-(2'- ethylhexyloxy)-1,4-phenylene vinylene], MEH-PPV, emission. At a porphyrin content of 0.25%, by weight, the emission is already dominated by the porphyrin. The PL efficiency of these copolymers is significantly reduced from the value of 13% for MEH-PPV down to 3% for the copolymer with 10.84% of porphyrin. Efficient energy transfer is also observed in the emission spectra of light-emitting diodes.

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Line shape of emission spectra of the luminescent polymer poly(p-phenylene vinylene)

Brazilian Journal of Physics ◽

10.1590/s0103-97332002000300018 ◽

2002 ◽

Vol 32 (2b) ◽

pp. 570-574 ◽

Cited By ~ 19

Author(s):

A. Marletta ◽

F. E. G. Guimarães ◽

R. M. Faria

Keyword(s):

Line Shape ◽

Emission Spectra ◽

Phenylene Vinylene ◽

Luminescent Polymer

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Synthesis and upconversion luminescence properties of CaF2:Yb3+,Er3+ nanoparticles obtained from SBA-15 template

Journal of Materials Research ◽

10.1557/jmr.2010.0255 ◽

2010 ◽

Vol 25 (10) ◽

pp. 2035-2041 ◽

Cited By ~ 18

Author(s):

Zhiguo Xia ◽

Peng Du

Keyword(s):

Electron Microscopy ◽

Upconversion Luminescence ◽

Emission Spectra ◽

Average Diameter ◽

Cubic Phase ◽

Pumping Power ◽

X Ray Diffraction ◽

Temperature Dependent ◽

X Ray ◽

Transmission Electron

CaF2:Yb3+,Er3+ upconversion (UC) luminescence nanoparticles have been synthesized using mesoporous silica (SBA-15) as a hard template. The samples were characterized by x-ray diffraction, Fourier transform infrared spectra, field-emission scanning electron microscopy, transmission electron microscopy, and UC emission spectra, respectively. Highly crystalline cubic phase CaF2:Yb3+,Er3+ nanoparticles are uniformly distributed with an average diameter of about 40–50 nm, and the formation process is also demonstrated. The UC fluorescence has been realized in the as-prepared CaF2:Yb3+,Er3+ nanoparticles on 980-nm excitation. The UC emission transitions for 4F9/2–4I15/2 (red), 2H11/2–4I15/2 (green), 4S3/2–4I15/2 (green), and 2H9/2–4I15/2 (violet) in the Yb3+/Er3+ codoped CaF2 nanoparticles depending on pumping power and temperature have been discussed. The UC mechanism, especially the origin on the temperature-dependent UC emission intensities ratio between 2H11/2 and 4S3/2 levels, have been proposed.

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