Open-circuit Voltage Of Device Research Articles

Acid versus base peptization of mesoporous nanocrystalline TiO2 films: functional studies in dye sensitized solar cells

We report an analysis of the influence of acid/base conditions employed in the synthesis of TiO2 nanoparticles upon the performance of dye sensitised photoelectrochemical solar cells fabricated from these particles. The functional properties of the TiO2 nanoparticles in these devices are investigated by potential step chronoamperometry, transient laser spectroscopy, and photovoltaic device characterisation. We find that base peptization conditions employed in the sol–gel fabrication of the TiO2 nanoparticles result in a reduction in film electron density under negative applied bias, correlated with slower interfacial recombination losses and a higher device open circuit voltage.

Characterization of Organic p/n Junction Photodiodes Based on Poly(alkylthiophene)/Perylene Diimide Bilayers

Photoconduction of bilayer organic p/n junction photocells can be finely tuned through the alteration of either the side chain orientation (regiorandom vs regioregular) or main chain structure in poly(3-alkylthiophene)s (P3ATs), where the incorporation of an electron-donating group (EDOT) appears to be an excellent method for enhancing the photoconduction. Moreover, doping of P3ATs proved to be an equally viable route for tuning the device characteristics. These polymers were used to fabricate bilayer organic photocells with the polymer as the p-type layer and 1,2-diaminobenzene perylene-3,4,9,10-tetracarboxylic acid diimide (PV) as the n-type layer. Action spectra at steady-state illumination demonstrated that all the interfaces (organic−organic p/n junction and organic−electrode) are actively involved in the photogeneration of carriers. Experiments showed that critical device properties, for example, open-circuit voltage (Voc) and short-circuit current (Isc), are not only dependent on the selection of electrodes and organic materials but also greatly affected by the illumination wavelength and intensity.

Open-Circuit Voltage Characteristics in Polyfluorene Based Photovoltaic Devices

AbstractIn this work the origin of the open-circuit voltage is studied in bi-layer devices based on polyfluorenes. The devices were fabricated using a lamination technique, which avoids the problems that usually arise when making well-defined bi-layers from soluble polymers. Often the open-circuit voltage in devices is attributed to the difference in the workfunctions of the electrodes. Whilst a cathode dependence of the open-circuit voltage was observed here, an additional constant voltage of ∼1V was also present in the devices investigated. We conclude that this additional open-circuit voltage is largely a result of a photo-induced dipole at the donoracceptor interface. This dipole is formed by charges that are separated as a result of exciton dissociation when the device is illuminated. Devices where the order of the polymer layers was reversed showed very different open-circuit voltages which confirms that the open-circuit voltage is heavily dependent on the structure of the active layer in the device. The effects of device thickness and excitation intensity on open-circuit voltage are also discussed.

The role of boron profiling in enhancing the performance of amorphous silicon-based alloy p-i-n solar cells

We have carried out a theoretical investigation of the effect of boron profiling on the performance of amorphous silicon-based alloy p-i-n solar cells. We show that the improvement in carrier collection is primarily caused by a rearrangement of the electric field distribution within the cell as well as by a relatively less important increase in the hole lifetime. It is also shown that boron profiling can increase the open-circuit voltage of devices with low built-in potentials.

Vertical multijunction solar-cell one-dimensional analysis

The vertical multijunction solar cell is a photovoltaic device which may allow conversion efficiencies higher than conventional planar devices. A one-dimensional model of the device is presented here which allows a simple and straightforward analysis of device performance to be conducted. The analysis covers the derivation of device short-circuit current, saturation current, open-circuit voltage, and maximum power as a function of illumination spectra, device geometry, and device material properties.

Comparison of Exact and Measured Open Circuit Photoconductor Voltages

It is necessary to determine the open circuit voltage of a photoconductor in order to find its responsivity and detectivity. The ideal case of a photodetector in series with an ideal current source is analyzed and an expression for the open circuit device voltage is given. Since this case is almost impossible to obtain in the laboratory with devices of 10x Ω internal impedance where x>7 and a bias of several hundred volts across the device is needed, the realistic nonideal current source case is treated. It is shown that what is believed to be the actual open circuit device voltage can be incorrect by as much as 10% in certain cases. The conditions necessary for accuracy are given along with curves enabling one to determine accurately the device open circuit voltage if these conditions are not met.