Photocurrent power point

The fill factor is obtained by dividing the product of current and voltage measured at the power point by the product of short-circuit current and the open-circuit voltage. The power point is the maximum product of the cell voltage and the photocurrent obtained on the I V plot (see Section 9.16.4.5). The open-circuit voltage is the potential of the illuminated electrode, where the short-circuit current (7SC) is zero. 

Figure 5. Output characteristics and photocurrent density at maximum power point against time (inset) for an intrinsic a-Si H photoanode-based cell. (Reproduced from Ref. 5.)...

Figure 8. Hypothetical photocurrent-voltage curve measured in a two-electrode arrangement. The short circuit photocurrent, isc, open circuit photovoltage, Vqc. and power point are indicated.

From Fig. 7 the calculation of the power conversion efficiency rj can be derived only the fourth quadrant of the I-V curve represents deliverable power from the device. One point on the curve, denoted as maximum power point (MPP), corresponds to the maximum of the product of photocurrent and voltage and therefore power. The ratio between Vmpp mpp (or the maximum power) and Vqc he is called the fill factor (FF), and therefore the power output is written in the form Pmax = oc fsc FF- Division of the output power by the incident light power res ults in the power conversion efficiency rj ... 

Fig. n.78 A current-voltage characteristic l(V) from a photovoltaic cell without and with illumination (dark and light characteristics). Uc is the short-circuit photocurrent, Voc the open-circuit voltage, and MPP the maximum-power point, where the power is Pmax-... 

The maximum power point of efficient solar cells is located close to the open circuit voltage (see Figures 2.12 and 2.89). For p-type semiconductors, the open circuit condition is the most anodic potential at which the photocathode is operated and anodic dark currents compensate the cathodic photocurrent at this potential. 

Figure 12.3 Typical photocurrent-voltage characteristics in a solar cell.Jsc is the short-circuit current density, Voc is the open-circuit voltage, and /mpp and Vmpp are the current and voltage at the maximum power point, respectively.

Semiconductor-Liquid Junction From Fundamentals to Solar Fuel Generating Structures, Fig. 18 Photocurrent and photovoltage relationships in a tandem structure for water splitting MPP, maximum power point energy gap of photoanode (a) and... 

Suspended semiconductor nanoparticles also differ from high-aspect-ratio semiconductor photoelectrodes in another aspect. High-aspect-ratio nanowire/macroporous photoelectrodes in low-level injection are connected to current collectors and are thus intended to operate at a specific power point (i.e., at a particular combination of current-potential values that maximizes the product of the quasi-Fermi-level splitting and the net photocurrent). In contrast, a suspended semiconductor nanoparticle functions without any external contacts at precisely open-circuit conditions. That is, at the operational conditions, photoexcited semiconductor nanoparticles suspended in a solution pass no net current, that is, 0=0, and their quasi-Fermi levels are offset by the maximum value possible under the operative illumination and recombination conditions. 

Figure 3.77 Evolution of open-circuit photovoltage, short-circuit photocurrent and the normalised product of these two representing conversion efficiency, for three monolithic DSCCs under xenon lamp illumination of 800 W m with cut-off below 435 nm. Each cell was connected to a 100 resistor for operation near the maximum power point dye, N3 electrolyte, 1 M TBAI and 0.1 M I2 in acetonitrile. Reprinted with permission from Kay and Gratzel, 1996 . Copyright (1996) Elsevier...

This equation holds only for an optical electric field which is Gaussian and which possesses an exponential autocorrelatitxi function, i.e., Eq. (66). If the field is non-Gaussian there is no simple relation between the optical spectrum lio)) and the power spectrum. Eq. (69) has three components (1) a shot noise term e(S ln which is independoit of the frequency (Le., white noise), (2) a d.a photocurrent 6(m) which is essentially infinite at extremely low fiequendes (i.e., d.c.) and a light beating spectrum which for an exponential autocorrelation function and Gaussian optical field is a Lorentzian of half width, IF. Fig. 4 shows the experimental data of Benedek et al with calculated points and observed line shape. What is not shown is the infinite d.c. photocurrent at ft)=0. These measurements were obtained by use of a spectrum analyzer which measures directly the power scattered at each frequency. 

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