Absorbed photon-to-current efficiency

Fig. 5.60 Absorbed-photon-to-current-efficiency APCE) of Ti-Fe-0 nanotube array samples at (a) 0.5 V bias, and (b) 0.7 V bias.

Another common and scientifically more relevant parameter is the quantum yield, x or APCEx (absorbed photon to current efficiency) where the optical absorption (A ) of the film is taken into account ... 

Ultrafast injection of carriers into the UO2 substrate suggests that overall cell efficiency is not limited by this process but by intervening transfer mechanisms (e.g., trapped state populations reducing quantum yield) or longer time scale electron-dye recombination rates (typically taking microseconds). For example, it was found that the absorbed photon to current efficiency (APCE) is considerably reduced for V compared to IV under identical cell conditions (27,55). While V has a 350 mV lower electrochemical reduction potential than IV (and hence a red-shifted absorption spectrum), it is unclear why the redder absorbing dye (V) does not inject as efficiently (56). Recent visible excitation with broadband... 

Absorbed Photon-to-Current Efficiency (APCE)/ Internal Quantum Efficiency (IQE)... 

PEC device efficiencies as measured by IPCE/EQE or STH implicitly include losses from impinging photons that are reflected or transmitted. To understand the inherent performance of a material, it is often helpful to subtract these losses and measure efficiency based only on photons absorbed. This is known as the absorbed photon-to-current efficiency (APCE), which describes the photocurrent collected per incident photon absorbed. APCE is synonymous with internal quantum efficiency (IQE). This is a particularly useful quantity to measure when studying thin films, since it helps to determine the optimum balance between maximal path-length for photon absorption versus minimal effective e /h" transport distance within the material. 

This required an exact determination of the quantum yield per absorbed photon. Since the absorption of a single QD layer is small, Eq. (9.34) is not useful. The authors defined instead an absorbed photon-to-current efficiency (APCE) determined by... 

The external quantiun yield or I PC E (incident photon to current efficiency) is defined as the quotient of the number of incident photons and the number of charge carriers output to the external circuit. It is smaller than the internal quantum yield for conversion of the absorbed photons into charge carriers within the cell, because it takes into account losses due to reflection, recombination, and scattering. In contrast to the internal quantum yield, which can attain values of nearly 100% (see above), the value of the external quantum yield can be measured directly from the short-circuit current density jsc. with jsc = Isc/A where A is the active area of the cell, and the incident light intensity is lo- At a given wavelength k, we have... 

Absorbed photon-to-current conversion efficiency. A term describing the photocurrent collected per incident photon actually absorbed. It is the IPCE normalized to the IQE. 

IPCE values in excess of 80% for the photo-oxidation of water have been reported for, e.g., WO3 [78] and for Ti02 under UV illumination [79], Another useful parameter is the APCE, or absorbed photon-to-current conversion efficiency. In contrast to the IPCE, the APCE also corrects for reflection losses. Often referred to as the internal quantum efficiency, it is related to the IPCE via... 

APCE Absorbed photon-to-current conversion efficiency... 

Another useful measurement is the spectral response of the cell, the Incident Photon-to-current Conversion Efficiency s (IPCE), given in Equation 3.13, or the Absorbed Photon-to-current Conversion Efficiency (APCE), given in Equation 3.14. 

In addition to being bound to T1O2 by carboxylate groups, this triruthenium(II) complex can be bound by peripheral sulfonate groups. These complexes absorb over a very broad range in the visible region of the spectrum, and monochromatic incident photon-to-current conversion efficiencies of over 80% have been observed... 

The key ingredient for new ways to harness sunlight is the solar cell, or photovoltaic (PV) cell, a device that absorbs photons from sunlight (or artificial sunlight) and generates an electrical current [9]. Figure 10.6 shows the evolution over time of photovoltaic cells since 1975 [4]. The first photovoltaic cell was a pn junction based on Si and had an efficiency of 5% to 6% [3] at present, Si pn junctions have overall power efficiencies of about 22% (maybe 10% in commerce) at the moment, Si solar cells are expensive but durable. 

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