Quantum efficiency measurement

YY04 Dy3+ Y203, Dy203 Can be used for calibration of optical equipment for quantum efficiency measurements.84... 

In Table E7.5, the fluorescence lifetimes and quantum efficiencies measured from different excited states of the Pr + ( Po and D2) and Nd + (" Fs ji) ions in a LiNbOs crystal are listed, (a) Determine the multiphonon nonradiative rate from the 19/2 and In/2 states of the Er + ion in LiNbOs. (b) If a fluorescence lifetime of 535 /us is measured from the excited state Fs/2 of the Yb + ion in this crystal, estimate the radiative lifetime from this state. 

Carrier and exciton dynamics in InGaN/GaN MQWs have also been studied at a high optical pumping power [34], At 7 K, a radiative decay lifetime of 250 ps was observed for the dominant transition at a generated carrier density of 1012/cm2. The time-resolved measurement showed that the decay of PL has a bimolecular recombination characteristic. At room temperature, the carrier recombination was found to be dominated by non-radiative processes with a measured lifetime of 130 ps. Well width dependence of carrier and exciton dynamics in InGaN/GaN MQWs has also been measured [35]. The dominant radiative recombination at room temperature was attributed to the band-to-band transition. Combined with an absolute internal quantum efficiency measurement, a lower limit of 4 x 10 9 cm3/s on the bimolecular radiative recombination coefficient B was obtained. At low temperatures, the carrier... 

By referring back to the I- V relationship in Eqs. (6) and (17) and Rs expressed in terms offix in Eq. (14), the fill factor and normalized efficiency, as shown in Fig. 11, are determined as a function of the electron /it product. These relationships shown in Fig. 11 could be tested by utilizing recent work by Faughnan, Moore, and Crandall in which the electron collection length in the cell s i layer at JT = Jx are determined from quantum efficiency measurements at various bias potentials applied to the cell (Faughnan et al., 1984). The collection length at V= 0 is a product of fix times the internal electric field and the internal field may be determined by the theory from the potential drop across Rs at JT = JK. Fill factor and efficiency data as a function of the fix product extracted from the electron collection length before and after extended cell illumination can be used to test this proposed model. 

Photoelectrolysis of Water in Cells with Ti02 Anodes Both single crystal and polycrystalline TiCte used and external quantum efficiency measured. 226... 

The field of photorefractivity in organic polymers and glasses has been in existence for less than a decade. The understanding of charge generation in these materials (which are often composites) is not yet mature, and the behavior of some of the more common constituents is understood better. Much of the literature on photo-refraetivity deseribes free earrier generation quantum efficiency measurements only briefly, before a more detailed discussion of other factors such as mobility and electro-optic response. Some of the relevant information pertinent to free carrier generation in these materials is presented here, to be followed by a review of this aspect of the amorphous photorefractives literature. 

Figure 4-36. Top panel Contributions of different processes to the ()(1 D) quantum yield as a function of wavelengths between 305 and 329 nm. The solid and broken lines represent the quantum efficiencies measured at 295 K and 227 K, respectively. Shaded region 1 shows the contribution of the hot band excitation process leading to the formation of ()(11)) via Reaction (4.ff4b) at 295 K. Region If (in black) represents the contribution of the spin-forbidden dissociation (4.114c). Region 111 corresponds to the 0(1D) formation via Reaction (4.114b) following excitation of ozone at ground vibration state. Bottom panel 0(1D) quantum efficiency as a function of temperature at 305, 308, 310 and 312 nm. Laboratory measurements are compared to recommendations (dashed lines) by JPL (1997). From Takahashi et al. (1998).

It should be noted already at this stage, that while the microscopic insight into the mode of operation of energy transfer is of academic interest mainly, the quantum efficiency measurements which are studied in this laboratory (2), by Parke and Cole (7) and Soules et al. (8) are of practical interest. 

A. Migdall, Absolute quantum efficiency measurements using correlated photons Toward a measurement protocol, IEEE Trans, on Instrumentation and Measurement 50, 478-481 (2001)... 

A.L. Migdall, R.U. Datla, A. Sergienko, J.S. Orszak, Y.H. Shih, Absolute detector quantum-efficiency measurements using correlated photons, Metro-logia32, 479-483 (1995)... 

Photocurrent spectra from a series of lateral PTCBI/TPD devices are shown in Fig. 5.20. A single 5nm film of TPD yields no measurable efficiency. The response of a single 10 nm film of PTCBI is represented by the dotted line. Responses of bi-layer heterojunctions of PTCBI/TPD are represented by the dashed and solid lines. In quantum efficiency measurements, the generated... 

Quantum Efficiency Measurements, U.S. Department of Energy (2005), http //wwwl.eere. energy.gov/solar/quantum efficiency.html. Accessed 1 Jan 2010... 

Table I shows dut measurable gains in efficiency are possible using a high performance spectrum shifting dye (high quantum yield and low emission loss) for a dual-junction GaAs based crystalline solar cell. Since die two junctions were likely well current-matched, die additional photons were assumed to be emitted at two different wavelengths, with each wavelengdi being absorbed by a different junction. This was necessary because the two junctions are connected in series and therefore an increase in current production by one junction will be limited by the current production of the other junction. Therefore, the photons where divided such that the addition current added to each junction was equivalent. Quantum efficiency measurements showed that the top junction was active with minimum bottom junction absorption at 490 nm and that the bottom junction was active at 800 run widi minimal top junction absorptioiL The shifted photons were therefore split between 490 nm and 800 nia The external quantum efficiency of die device was 0.8 and 0.88 at 490 nm and 800 nm, respectively.

For the triple junction a Si device, the top cell was assumed to be current limiting. It was assumed that the other two junctions (middle and bottom) had sufficient current producing crqiacity to match the increase in the top cell current caused by the additional photons. External quantum efficiency measurements of the device showed that the top junction absorbs at 470 nm with an external quantum efficiency of 0.78 without significant absorption fi om the middle and bottom junctions. Therefore, a wavelength of470 nm was assumed for emission of the shifted photons. The calculated results based on these assumptions are presented in Table II. 

However, the quantum efficiency measured there was much lower than that measured in Shanghai even with the same pot of wheat(Tab.4). 

Quantum Efficiency Measure of the percentage of photons hitting a device that will produce electrons. 

Margulis GY, Hardin BE, Ding IK, Hoke ET, McGehee MD (2013) Parasitic absorption and internal quantum efficiency measurements of solid-state dye sensitized solar cells. Adv Energ Mater 3(7) 959-966... 

Nevertheless, quantum efficiency, measured by the integrated sphere technique, was 32%, not yet good enough for the luminescent collection application, which requires near 60% conversion of absorbed to luminescent energy. Also optical scattering should be lower. 

Recently, Baumann et al.(43) have measured time-resolved photoconductivity in PDA-TS-6 crystals as well as polyacetylene excited by 25 ps pulses of a Nd YAG laser (ftU) = 2.3 eV). The response time of the detector was 200 ps. The transient signal shown in fig.5 reveals a fast initial peak with instrument-limited pulse-shape followed by a slower decaying tail. The field dependence of the peak height (fig.6) parallels that of the carrier generation process and is in accord with what Donovan and Wilson have found on a 20 ns time resolution. The quantum efficiency associated with the fast photocurrent peak is 1.5x10 times the dc-quantum efficiency measured at hu) = 2.7 eV. 

FIGURE 15. Schematic of apparatus for potential modulation quantum efficiency measurements. Central inset illustrates potential waveform. 

H) Photovoltaic external quantum efficiency Measurements of the current-voltage characteristics of an OPV cell in the dark and under the illumination, as shown in Figure 10, allow the determination of its fundamental photovoltaic parameters. ... 

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