Tm3+ and Yb3+ co-doped upconverting (UC) glass phosphors were used to converting near-infrared to visible light and input to a CdS/CdTe solar cell, therefore to enhance solar cell’s response in the near-infrared of the sub-bandgap region. Current-voltage measurements were performed on the solar cell with a UC glass phosphor. A short-circuit photocurrent enhancement of 31 μA was obtained using a Tm3+and Yb3+ co-doped glass UC phosphor, illuminated by a 980 nm diode laser at 100 mW. This photocurrent response corresponds to external quantum efficiency (EQE) of 0.04 % at 980 nm. For full collection of the UC light in 4π solid angle, the EQE value is expected to reach 1.6 %. The photo-current observed was proportional to the effective UC light intensity from glass UC phosphor. A non-linear relation between the output photo-current and the incident power of the infrared light was observed, similar to the relation between UC intensity and the incident power. UC efficiency of the glass phosphor was calculated using EQE values at both UC wavelengths and at 980 nm.
We investigated the upconversion and downconversion luminescence in (Tb3+, Yb3+) and (Tb3+, Yb3+) co-doped lithiumlanthanum- aluminosilicate oxyfluoride glass. Upon excitation at 980 nm, where crystalline CdTe solar cells no longer absorb, the sub-bandgap photons can be converted to the higher-energy ones via upconversion. In addition, under excitation between 470 nm and 490 nm, one blue photon might be split up to two near-infrared ones via downconversion. The downconversion luminescence matches the spectral response of crystalline Si solar cell well. We observed much more intense upconversion luminescence from (Tm3+, Yb3+) codoped glass than that from ( Tb3+, Yb3+) codoped glass under the same 980 nm excitation conditions. Our results indicate that the sequential energy transfer from Yb3+ ions to Tm3+ ions is much more efficient than the cooperative energy transfer from Yb3+ ions to Tb3+ ions.
Photoluminescence (PL) of Er-doped ZnO nanoparticle films was studied. The films were grown on silicon (100) or fused silica substrates using e-beam evaporation and subsequently annealed at 700 °C in air for an hour. PL was measured at two excitation wavelengths, 325 and 514.5 nm. The 325 nm was used for exciting the host semiconductor ZnO while 514.5 nm was used for directly exciting Er3+ ions in the ZnO host. Er3+ luminescence was observed from annealed films using either indirect (325 nm) or direct (514.5 nm) excitations. It has been found that the indirect excitation is significantly more efficient than the direct excitation in producing 1.54 μm photoluminescence. With indirect excitation, the Er3+ luminescence observed is attributed to energy transfer from ZnO host to the Er3+ ions doped. Energy transfer from e-h pairs resulting from ZnO host excitation may provide efficient routes for exciting Er3+ ions inside nano-crystalline particles of the films.
Tb, Yb, and Ag co-doped glass nano-composites were synthesized in a lithium-lanthanum-aluminosilicate glass matrix
(LLAS) by a melt-quench technique. Ag nanoparticles (NPs) were formed in the glass matrix and confirmed by optical
absorption and transmission electron microscopy (TEM). Plasmon enhanced luminescence was observed. Cooperative
infrared to visible upconversion and visible to near-infrared quantum cutting were studied for samples with different
thermal annealing times. Because the Yb3+ emission at 940 - 1020 nm is matched well with the band gap of crystalline
Si, the quantum cutting effect may have its potential application in silicon-based solar cells.
Recently a melt-processed blend of
1,4-bis(α-cyano-4-octadecyloxystyryl)-2,5-dimethoxybenzene (C18-RG) dye and
polyethylene terephthalate glycol (PETG) has been demonstrated as a promising 3-dimentional optical data storage
(ODS) medium 1. ODS in this novel system relies on the laser-induced switching of the aggregation state of the excimerforming
fluorescent dye in the inert host polymer. Here we investigate the mechanism and the time scales involved in the
writing process. The optical writing was realized by the laser-induced localized excimer to monomer conversion and was
characterized by the emergence of the monomer fluorescence. We obtained the dependence of the excimer to monomer
conversion on the writing time. Our result indicates that the effective optical writing time is controlled by heating and
cooling time of the host polymer and the excimer-to-monomer conversion time. The effective laser writing time, under
the specific writing conditions employed in our experiments, is on the order of 10 ms.
Tb3+ and Ag co-doped glass nano-composites were synthesized in a glass matrix Li2O-LaF3-Al2O3-SiO2 (LLAS) by a melt-quench technique. The growth of Ag nanoparticles (NPs) was controlled by a thermal annealing process. A broad absorption band peaking at about 420 nm was observed due to surface plasmon resonance (SPR) of Ag NPs. The intensity of this band grows with increasing annealing time. The transmission electron microscopic image (TEM) reveals the formation of Ag NPs in glass matrix. Photoluminescence (PL) emission and excitation spectra were measured for glass samples with different Ag concentrations and different annealing times. Plasmon enhanced Tb3+ luminescence was observed at certain excitation wavelength regions. Luminescence quenching was also observed for samples with high Ag concentration and longer annealing time. Our luminescence results suggest that there are two competitive effects, enhancement and quenching, acting on Tb3+ luminescence in the presence of Ag NPs. The enhancement of Tb3+ luminescence is mainly attributed to local field effects due to SPR. The quenching of luminescence suggests an energy transfer from Tb3+ ions to Ag NPs.
Tb3+ and Ag co-doped glass nano-composites are synthesized in a glass matrix Li2O-LaF3-Al2O3-SiO2 (LLAS) by a melt-quench
technique. The nucleation and growth of Ag nanoparticles (NPs) were controlled by a thermal annealing process.
A broad absorption band peaking at about 420 nm was observed due to surface plasmon resonance (SPR) of Ag NPs.
Annealing of glass samples results in the growth of Ag NPs. Photoluminescence (PL) emission and excitation spectra
were measured from glass samples with different Ag concentrations and different annealing times. Plasmon enhanced
Tb3+ luminescence was observed at certain excitation wavelength regions. Luminescence quenching was observed for
samples with high Ag concentration and longer annealing time. Our luminescence results suggest that there are two
competitive effects, enhancement and quenching, acting on Tb3+ luminescence in the presence of Ag NPs. The
enhancement of Tb3+ luminescence is mainly attributed to local field effects: the SPR of Ag NPs causes an intensified
electromagnetic field around the NPs, resulting in enhanced optical transitions of Tb3+ ions in the vicinity. The
quenching effect in the presence of Ag NPs suggests an energy transfer from Tb3+ ions to Ag NPs. The competition
between the plasmonic enhancement and the quenching effect is discussed for samples with different Ag concentrations
and annealing times.
Undoped and doped CdS0.8 Se0.2 crystals were grown by physical vapor transport (PVT). The selected dopant was vanadium at a nominal concentration of 150 ppm creating for photorefractive effect. The as-grown crystal has a large crystal size, 1.1 cm in diameter and 6 cm in length, with a medium resistivity of 104 - 107 (Omega) -cm. The results from low temperature photoluminescence (PL) show that the undoped crystal has only one emission band at 2.31 eV and its phonon replicas. The vanadium doped crystal not only show the similar emission band but also has an additional broad band center at 1.95 eV due to the effect of doping. Low temperature (16 K) and room temperature IR transmittance spectra of vanadium doped crystal revealed a broad absorption band between 0.8 and 1.3 eV which may be due to vanadium dopant. Etch pitch density (EPD) measurements were performed, and the results showed EPD in the range of 104/cm2 for both types of crystals. Precipitate/inclusion were also found in both crystal, and their distribution patterns may be related to gravity-induced convection during growth process.
Infrared reflectance between 4000 and 100 cm-1 and optical spectra between 1.8 and 6.2 eV of high purity silica implanted with nominal doses of 1, 3, and 6 X 1016 Pb ions/cm2 were recorded before and after annealing at 400, 600, and 800 degree(s) C for 1 hour. Curve resolution analysis of the Si-O stretching region resulted in six peaks which were characterized by their lineshape parameters. The oscillator strength of the ion induced defect peak at 1035 cm-1 was found to depend on ion dose. The defect band at 1035 cm-1 decreased to an intensity comparable to that of the unimplanted glass after thermal annealing for 1 hour at 800 degree(s) C. Far infrared spectra indicated the formation of lead silicate particles after annealing.
Two optical methods were recently developed for in situ monitoring of the growth process of mercuric iodide crystals. The first method uses resonance fluorescence spectroscopy (RFS) for the determination of iodine vapor present in the growth ampule, which is an important parameter in determining the stoichiometry, and therefore the quality of the crystals. The second method, reflectance spectroscopy thermometry (RST) measures the crystal face temperature with a present accuracy of +/- 1.5 degree(s)C.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.