Incident-photon-to-current efficiencies

Quite differently, Pleux et al. tested a series of three different organic dyads comprising a perylene monoimide (PMI) dye linked to a naphthalene diimide (NDI) or C60 for application in NiO-based DSSCs (Fig. 18.7) [117]. They corroborated a cascade electron flow from the valance band of NiO to PMI and, finally, to C60. Transient absorption measurements in the nanosecond time regime revealed that the presence of C60 extends the charge-separated state lifetime compared to just PMI. This fact enhanced the device efficiencies up to values of 0.04 and 0.06% when CoII/m and P/Ij electrolytes were utilized, respectively. More striking than the efficiencies is the remarkable incident photon-to-current efficiency spectrum, which features values of around 57% associated to photocurrent densities of 1.88 mA/cm2. 

Fig. 3.24 Incident photon to current efficiency (IPCE) spectrum of a titania nanotube array photoelectrode.

Steady-state wavelength-specific photocurrents were measured for the Ti-Fe-0 films in a two-electrode arrangement at different applied voltages. Incident photon-to-current efficiencies (IPCE) are calculated using the following equation ... 

The performance of the cell can be quantified on a macroscopic level with parameters such as incident photon to current efficiency (IPCE), open-circuit photo voltage (Voc), and the overall efficiency of the photovoltaic cell (i7ceM). 

D. Incident Photon to Current Efficiency and Open-Circuit Photovoltage... 

Fig. 4. Dependence of incident photon to current efficiency (IPCE) on excitation wavelength and presence of current-doubling agent. ITO electrodes were covered with P25 (squares) or 3% [PtCl4]/P25 (circles) and biased at a constant potential of 0.7 V vs. Ag/AgCl in 0.1 M NaOH solution (a)). After addition of 0.1 M HCOONa the IPCE values increased (open circles, (b)). The inserts show the zoomed visible region.

Under steady-state conditions, that is, under constant irradiation, the incident photon-to-current efficiency (IPCE) as a function of the wavelength k can then be given in terms of these reactions as follows ... 

The spectral response, or action spectrum, of a phototodiode is obtained by measuring the electrical response of the device upon monochromatic illumination over a wide range of wavelengths. The external quantum efficiency ij, often also called the incident photon-to-current efficiency (IPCE) of the device, is the ratio of the measured photocurrent (in electrons per unit area and time) to the intensity of incoming monochromatic light in photons per unit area and time. Explicitly,... 

Figure 3.2.3 Incident photon-to-current efficiency (left, circles) and UV-visible absorption spectrum (right, solid line) of 1 ym thick Sn02 film modified with 1c...

Figure 20 (a) Absorption spectrum of (a) 17 adsorbed on TiOj particulate film and (b) action spectrum of incident photon to current efficiency of OTE/TiOj/l . Inset shows linear dependence of short circuit current on the incident light intensity. (From Ref. 64.)... 

Figure 32. Photocurrent spectra of the electrodes of Figure 31. IPCE, incident photon to current efficiency, sulfide electrolyte.

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... 

Incident Photon-to-Current Efficiency (IPCE)/External Quantum Efficiency (EQE)... 

Enhancing the catalysis at the surface of PEC electrodes results in a lower kinetic overpotential and an increase in photocurrent. The effectiveness of the catalysts after surface treatment can be determined by utilizing three-electrode j-V measurements (see Section Three-Electrode j-V and Photocurrent Onset ) as well as IPCE measurements (see Chapter Incident Photon-to-Current Efficiency and Photocurrent Spectroscopy ). It may also useful to perform Mott-Schottky (see Section Mott-Schottky ) to determine any impacts these catalysts may have on the band structure (e.g., due to Eermi level pinning). 

The incident photon-to-current efficiency (IPCE) is a measure of the ratio of the photocurrent (converted to an electron transfer rate) versus the rate of incident photons (converted from the calibrated power of a light source) as a function of wavelength. IPCE takes into consideration the efficiencies for photon absorption/... 

Incident Photon to Current Efficiency IPCE, also called external quantum efficiency, is the ratio of electrons collected at the terminals to incident... 

Fig. 4.9 Photoelectrochemical characterization of Si-doped Fc203 electrodes prepared by the APCVD technique. The left graph shows the current-voltage characteristics in darkness and under simulated sunlight (100 mW/cm ) at a scan rate of 50 mV/s. (a) Unmodified Fe203 (b) the same electrode after cobalt treatment. The right graph shows the incident photon-to-current efficiency (IPCE) spectrum of the same electrode at different conditions, (a) Unmodified Fc203 at 1.23 Yrhe (b) after cobalt deposition, at 1.23 Vrhe> (c) at 1.43 Vrhe, (d) at 1.03 Vrhe, (e) at 1.23 Vrhe but illuminated through the Sn02 substrate (f) absorption spectrum of this electrode. From [105] used with permission...

In calculations of efficiency, Xt is to be compared with the carrier lifetime in the space charge layer, Tr. From a qualitative standpoint, if Xi > Tr, a sizable proportion of minority carriers generated inside space charge layer will recombine before making it to the semiconductor/electrolyte interface. Taking a quantitative approach, Jarrett solved the diffusion equation for an illuminated planar semiconductor/electrolyte interface and calculated incident photon-to-current efficiency (IPCE) for systems with varying xJxb. [8]. One series of calculations used as... 

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