Up-conversion efficiency

The up-conversion efficiency is low and varies with the concentration of the activator and sensitisor ions. A maximum efficiency is observed with concentrations of about 1-3% of the active center. Above this value increasing back transfer from Er3+ to Yb3+ and increasing interactions between both lanthanide ions, leading to cluster formation and Yb3+-Yb3+ energy transfer, limits the efficiency. 

Impact of Fuel Sulfur on Three-Way Catalyst Performance (warmed-up conversion efficiency at conditions shown during exposure to sulfur at the concentrations shown). 

Table V. Average Warm-Up Conversion Efficiencies FTP Cycles 1-5...

Recently, uniform Filins with high concentrations of Cwl were cast from 1,2-dichlorobenzene solutions containing up to 1 4 weight ratio MEH-PPV [110]. For devices made from these high concentration blends, charge collection efficiencies around //,.=26% (electron/incident photon) and power conversion efficiencies around tjc-2.5% (electrical power out/incident light power) have been realized. 

With commercially available YDFL as pumps, powers > 40 W at 1178 nm are feasible. This sets an upper limit to the conversion efficiency needed in the subsequent second harmonic generation. Numerical simulations for the amplifier and resonator Raman laser configuration indicate feasibility of the system with sufficient SBS suppression. ESO has assembled the amplifier configuration, and has demonstrated up to 4 W CW at 1178 nm. ESO s goal is to have compact and turnkey commercial fiber lasers for LGS/AO within 3 years. 

As it has been described in various other review articles before, the conversion efficiencies of photovoltaic cells depend on the band gap of the semiconductor used in these systems The maximum efficiency is expected for a bandgap around Eg = 1.3eV. Theoretically, efficiencies up to 30% seem to be possible . Experimental values of 20% as obtained with single crystal solid state devices have been reported " . Since the basic properties are identical for solid/solid junctions and for solid/liquid junctions the same conditions for high efficiencies are valid. Before discussing special problems of electrochemical solar cells the limiting factors in solid photovoltaic cells will be described first. 

A modern variation on the rapid scan spectrometer, which is under development, uses a laser-generated plasma as a high intensity broad-band IR source (65). This method has been used to probe the vc—o absorption of W(CO)6. Another technique TRISP (time-resolved IR spectral photography), which involves up-conversion of IR radiation to the visible, has also been used to probe transients (66). This method has the enormous advantage that efficient phototubes and photodiodes can be used as detectors. However, it is a technically challenging procedure with limitations on the frequency range which depend on the optical material used as an up-converter. 

Thus, the catalyzed process represented by (14) is only downhill for sufficiently low pH at the lower pH s the driving force is greater and the rate is faster. However, as the pH is lowered Ey becomes smaller. This leads to an optimum in overall energy conversion efficiency at pH =4. For monochromatic 632.8 nm light the efficiency for photoasslsted H2 evolution is up to 5% whereas naked electrodes have negligible efficiency.(49,50)... 

Enhancement of x2 will lead to improvement (in terms of efficiency per interaction volume) in the following applications up-conversion in the visible or near U.V. of powerful I.R. laser radiation, frequency modulation of a laser carrier beam, optical parametric oscillation and amplification for solid state infrared tunable coherent devices. 

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