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Optimizing infrared to near infrared upconversion quantum yield of β-NaYF4:Er3+ in fluoropolymer matrix for photovoltaic devices
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10.1063/1.4812578
/content/aip/journal/jap/114/1/10.1063/1.4812578
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/1/10.1063/1.4812578

Figures

Image of FIG. 1.
FIG. 1.

Energy level diagram of Er and UC mechanisms for I to I excitation. UC emissions are shown as dashed-dotted arrows, GSA/ESA as dashed arrows, and ETU processes as solid arrows. The curved arrows represent fast multi-phonon relaxations.

Image of FIG. 2.
FIG. 2.

(a) I → I absorption of PFCB pellets with 55.6 w/w% β-NaYF:Er for different Er concentrations. (b) I → I Er emissions for an excitation at 1523 nm with power density of 970 ± 43 Wm. (c) Scatter spectra of 25 mol% Er sample (black solid curve) and of the corresponding reference sample (red dashed curve). The area under the red dashed curve gives the number of photons incident whereas the difference in the area under the two curves gives the number of photons absorbed. For comparison, the corresponding absorbance spectrum of the sample is shown (blue dotted curve). (d) The and for different Er concentrations of 55.6 w/w% β-NaYF:Er samples in a PFCB matrix at an incident pump power density of 970 ± 43 Wm.

Image of FIG. 3.
FIG. 3.

Variation in the (a) and (b) as a function of excitation power density for different Er concentrations. The log-log plots of the (c) and (d) versus the power density show deviations from a linear behavior for high power density and high Er concentrations. The lines are fits to the low (solid lines) and high (dotted lines) power density ranges, respectively. Note that for clarity, the corresponding error values [±10% in the and ±4.4% in the power density] have not been included in the figures.

Image of FIG. 4.
FIG. 4.

Normalized excitation spectra of the four Er UC emission bands: (i) I → I at 980 nm (solid curve), (ii) II at 810 nm (dashed curve), (iii) F → I at 664 nm (dashed-dotted curve), and (iv) H-S → I at 542 nm (dotted curve). All excitation spectra clearly resemble the I → I absorption, which indicates that ETU is the dominant UC mechanism.

Image of FIG. 5.
FIG. 5.

(a) RT temporal evolution of the I UC emission at 980 nm upon pulsed I excitation at 1523 nm of β-NaYF:Er samples with 25 mol% and 75 mol% Er. The inset shows a semi-log plot for the 25 mol% sample. (b) The rise (open square) and decay (solid square) times for different Er concentrations were obtained from fits as shown in (a) to a Vial type equation. The lines are a guide to the eye.

Image of FIG. 6.
FIG. 6.

(a) I → I absorption spectra of various concentrations (55.6 to 84.9 w/w%) of β-NaYF:25%Er in PFCB pellets. (b) I → I UC emission spectra upon I → I excitation at 1523 nm with power density of 970 ± 43 Wm.

Image of FIG. 7.
FIG. 7.

(a) and of samples with different concentrations of β-NaYF:25%Er in the PFCB matrix for an incident pump power density of 700 ± 31 Wm (up triangles) and 970 ± 43 Wm (squares). Scatter spectra of reference (solid curve) and the sample (dashed curve) with (b) 55.6 w/w%, and (c) 84.9 w/w% of β-NaYF:25%Er in PFCB matrix at excitation (1523 nm) power density of 970 ± 43 Wm. The difference between the area under the scatter curve for reference and the corresponding sample gives the number of photons absorbed (shaded region). Clearly, the sample with 84.9 w/w% absorbs more photons than the sample with 55.6 w/w% of β-NaYF:25%Er in PFCB matrix.

Image of FIG. 8.
FIG. 8.

Scatter spectra of reference (solid curve) and the sample (dashed curve) with (a) 84.9 w/w% of β-NaYF:25%Er in PFCB matrix and (b) 100w/w% β-NaYF:25%Er powder at excitation (1523 nm) power density of 700 ± 31 Wm. The difference between the area under the scatter curve for reference and the corresponding sample gives the number of photons absorbed (shaded region). Clearly, the sample with 84.9 w/w% of β-NaYF:25%Er in PFCB matrix absorbs more photons than the powder sample with 100 w/w% of β-NaYF:25%Er. (c) I I UC emission spectra upon I I excitation at 1523 nm with power density of 700 ± 31 Wm for 84.9 w/w% (solid curve) of β-NaYF:25%Er in PFCB matrix and 100 w/w% β-NaYF:25%Er powder (dotted curve).

Tables

Generic image for table
Table I.

(a) The gradient values of linear fits for the log-log plots of the versus the power density in the low and high power regions as a function of Er doping [in β-NaYF:Er PFCB pellets], see Figure 3(c) . (b) The gradient values of linear fits for the log-log plots of the versus the power density in the low and high power regions as a function of Er doping in β-NaYF:Er PFCB pellets, see Figure 3(d) .

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/content/aip/journal/jap/114/1/10.1063/1.4812578
2013-07-03
2014-04-23
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Optimizing infrared to near infrared upconversion quantum yield of β-NaYF4:Er3+ in fluoropolymer matrix for photovoltaic devices
http://aip.metastore.ingenta.com/content/aip/journal/jap/114/1/10.1063/1.4812578
10.1063/1.4812578
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