Open-Circuit Voltage Voc

Variation of Acceptor Strength. Photovoltaic parameters were determined under illumination with 60 mW/cm2 white light from a halogen lamp. 

Experimental results on the variation of the acceptor strength and on the variation of the top electrode work function are summarized in Figs. 5.34a 

The influence of the work function of the negative electrode on the value of Voc for MDMO-PPV/PCBM solar cells is shown in Fig. 5.34b. It is important to note that the x-axis now covers more than 2 eV. Once again, a linear model is fitted to the experimental data and a slope of S2 0.1 is calculated as the best fit. This result shows that the work function of the metal has a considerably weaker effect on the Voc values than the reduction potential. 

In order to understand this behavior, we introduce a concept developed to explain the built-in potential for inorganic semiconductor/metal interfaces and which is based on the index of interface behavior S [121]. This parameter S is defined as the slope in a diagram, where the blockade potential of a semiconductor/metal interface is plotted against the work function of the metal  

In addition, the presence of surface charges leads to band bending at the semiconductor-metal interface. For /(-type semiconductors, these states are acceptor-like and the semiconductor at equilibrium may exhibit upward (negative) band bending as the surface Fermi level moves towards the charged 

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Maximum Power Output (WM) and Open-Circuit Voltage (Voc) for SOFCs with Doped-Ceria Electrolytes... 

The photocurrent density of nanotube array samples fabricated in an electrolyte of 1.2 g of NH4F in a solution of 5 ml deionized water + 95 ml formamide at 35 V is shown in Fig. 5.46(a). The resulting nanotube array samples were 30 pm in length, with an outer diameter of 205 nm. The samples were annealed at 525°C and 580°C for 1 hour in oxygen prior to measurement. The 580°C annealed sample had an open circuit voltage Voc of -0.925 V (vs. Ag/AgCl) the 525°C annealed sample had an open circuit voltage... 

If the photoanode is not connected to the counterelectrode, then current cannot flow, and instead the potential of the photoanode (the Fermi level) rises until balanced by recombination of the photogenerated charges (Fig. 9.6b). The difference between this potential under illumination and the original potential (more correctly, the potential of the counterelectrode, which ideally is equal to that of the nonilluminated photoelectrode) is the open-circuit voltage (Voc) of the cell. 

Under illumination with a light source, a typical solar cell exhibits the current-voltage characteristics shown in Figure 3. The current drawn by the cell when the terminals are connected to each other is the short circuit current (7SC, in mA/cm2). In the presence of an external load with infinite resistance (open circuit condition), the voltage developed is the open-circuit voltage (Voc, in V). 

The overall efficiency, rjsi0bai, of the photovoltaic cell depends on the integral photocurrent density, zph, which represents the overlap between the solar light envelope and the monochromatic current yield, the open-circuit voltage, Voc, the fill factor of the cell iff), and the light intensity, Is, as shown in the following ... 

Fig. 8.2. J/V-curve with description of solar cell parameters efficiency /, fill factor FF, open circuit voltage Voc, and short circuit current density Jsc- The photogenerated current density Jph is indicated by the dotted line. More details of these and all other parameters are given in the text...

Fig. 8.24. Open circuit voltage Voc of a-Si H solar cells prepared using a microcrystalline p-layer only (open squares) or a pc-Si H/a-Si H double p-layer design solid triangles) as function of pc-Si H-p deposition time. The thicknesses of the a-Si H-p-layers were kept constant between 5 and 10 nm [143]...

Fig. 4.8. Efficiency rj, open-circuit voltage Voc, and short-circuit current density jsc as a function of the band gap a of a 2-band system illuminated by blackbody radiation at 5 800 K with an incident energy current density of 1.39 kW/m2...

Open-circuit voltage (Voc)- This is the voltage output when the load impedance is much greater than the device impedance. 

Although reduction occurs spontaneously, most studies were carried out at constant applied potentials at various selected values in order to study the system in a controllable manner. Significant reduction of the (CH)X occurs only at an applied potential less than 1.7V (10). After the onset of reduction, the open circuit voltage, Voc, falls rapidly with increasing reduction up to a reduction level of 1% and then decreases more slowly. 

Figure 1. Open circuit voltage. Voc vs. tine characteristics of a...

When the cell is short circuited (V= 0), the short-circuit photocurrent Ec flows. With monochromatic illumination, one can obtain from it e.g. the spectral dependence of the charge-carrier generation. The voltage at which the current just ceases to flow is called the open-circuit voltage Voc- It is mainly determined by the energy... 

Figure 3.4 Dependences of photocurrent density (J J, open-circuit voltage (Voc). fill factor (FF), and energy conversion efficiency ri) on the amount of Ti02 loading on an ITO-PEN plastic electrode. Photocurrent density is normalized for constant incident...

For solar cells, the efficiency is given under irradiation with a solar spectrum under air mass 1.5 (AM 1.5) [65] in terms of power conversion efficiency or internal photon-to-electron conversion efficiency (ICPE) [66]. Characteristic parameters that are often used are the open circuit voltage Voc, the short circuit current density /sc, and the fill factor, given by... 

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