The Experts below are selected from a list of 81075 Experts worldwide ranked by ideXlab platform
Wolfgang Tress - One of the best experts on this subject based on the ideXlab platform.
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Maximum Efficiency and Open-Circuit Voltage of Perovskite Solar Cells
Organic-Inorganic Halide Perovskite Photovoltaics, 2016Co-Authors: Wolfgang TressAbstract:This chapter serves as an introduction to the general working principles of solar cells. It starts from the thermodynamics of terrestrial solar cells and fundamentals of semiconductor-based photovoltaics, where the theoretical limits of efficiency and Open-Circuit Voltage as a function of the bandgap are discussed. The chapter describes the prediction of the Open-Circuit Voltage when the photovoltaic action spectra and the electroluminescence quantum efficiency are known. The role of subgap states and several sources of nonradiative recombination, including interfaces to the charge-transport layers, are investigated at Open-Circuit Voltage and fill factor of state-of-the-art perovskite solar cells. Based on these factors, organic–inorganic perovskite solar cells with different architectures and compositions are compared with other solar cell technologies. Low disorder and weak nonradiative recombination are shown to be responsible for the superior performance of mixed cation mixed halide perovskite solar cells, allowing for Open-Circuit Voltages of 1.2 V to be achieved at a bandgap of 1.6 eV.
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predicting the Open Circuit Voltage of ch3nh3pbi3 perovskite solar cells using electroluminescence and photovoltaic quantum efficiency spectra the role of radiative and non radiative recombination
Advanced Energy Materials, 2015Co-Authors: Wolfgang Tress, Olle Inganas, Nevena Marinova, Mohammad Khaja Nazeeruddin, Shaik M Zakeeruddin, Michael GraetzelAbstract:The remarkably high Open-Circuit Voltage of methylammonium lead iodide perovskite solar cells is investigated. Both the theoretical maximum and the real Open-Circuit Voltage are predicted from electroluminescence and photovoltaic external quantum efficiency spectra. Radiative and non-radiative recombination are quantified, where a source of non-radiative recombination is found in the mesoscopic structure, independent of the Al2O3 or TiO2 scaffold. Without a hole-transport layer, non-radiative recombination is strongly enhanced, which reduces the Open-Circuit Voltage. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Neil C. Greenham - One of the best experts on this subject based on the ideXlab platform.
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Open-Circuit Voltage Characteristics in Polyfluorene Based Photovoltaic Devices
MRS Proceedings, 2011Co-Authors: Catherine Ramsdale, Ana Claudia Arias, J. Devin Mackenzie, Richard H. Friend, Neil C. GreenhamAbstract: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.
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The Origin of Collected Charge and Open‐Circuit Voltage in Blended Polyfluorene Photovoltaic Devices
Advanced Materials, 2004Co-Authors: Henry J. Snaith, Neil C. Greenham, Richard H. FriendAbstract:The transport properties of the blended polyfluorene layers were studied using layered structures containing both pristine and the blended layers. It was shown that for a polymer blend device where there is a fine scale of phase separation, only charges generated close to either electrode can be collected. The Open-Circuit Voltage of a polymer blend device was found to be lower than that of a bi-layer device as a result of direct paths from cathode to anode of each component of the blend. The results show that a charge injection barrier from the electrodes into the polymer film helps to retain a high Open-Circuit Voltage in the blend
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The origin of the Open-Circuit Voltage in polyfluorene-based photovoltaic devices
Journal of Applied Physics, 2002Co-Authors: Catherine Ramsdale, Ana Claudia Arias, J. Devin Mackenzie, Richard H. Friend, J. A. Barker, Neil C. GreenhamAbstract:The influence of device structure on the Open-Circuit Voltage of polyfluorene-based photovoltaic devices has been investigated. Bilayers of hole- and electron-accepting polyfluorenes have been fabricated using an aqueous “float-off” lamination technique and subsequently incorporated into organic photovoltaic devices with a range of cathodes and anodes. A scaling of the Open-Circuit Voltage with electrode work function difference has been observed with an additional intensity- dependent contribution from the active layer within the device. This additional contribution is attributed to photoinduced generation of carriers, whereby accumulation of charge at the polymer–polymer heterojunction results in a dipole across the interface and gives rise to a diffusion current that must be counterbalanced by a drift current at Open Circuit.
Zh S Karazhanov - One of the best experts on this subject based on the ideXlab platform.
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Open Circuit Voltage decay transient in dislocation engineered si p n junction
Journal of Physics D, 2008Co-Authors: A Davletova, Zh S KarazhanovAbstract:This work presents a study of an Open-Circuit Voltage decay transient in dislocation-engineered Si p?n junctions. It is found that upon switching off the illumination the Open-Circuit Voltage decreases with time according to the exponential function, whereas the excess carrier concentration decreases with time according to the double exponential function. This result indicates that the dislocation-engineered Si p?n junctions are sensitive to variations of the band-to-band illumination intensity. It is found that the carrier lifetime and Open-Circuit Voltage can be modulated by ultrasound treatment.
Michael Graetzel - One of the best experts on this subject based on the ideXlab platform.
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predicting the Open Circuit Voltage of ch3nh3pbi3 perovskite solar cells using electroluminescence and photovoltaic quantum efficiency spectra the role of radiative and non radiative recombination
Advanced Energy Materials, 2015Co-Authors: Wolfgang Tress, Olle Inganas, Nevena Marinova, Mohammad Khaja Nazeeruddin, Shaik M Zakeeruddin, Michael GraetzelAbstract:The remarkably high Open-Circuit Voltage of methylammonium lead iodide perovskite solar cells is investigated. Both the theoretical maximum and the real Open-Circuit Voltage are predicted from electroluminescence and photovoltaic external quantum efficiency spectra. Radiative and non-radiative recombination are quantified, where a source of non-radiative recombination is found in the mesoscopic structure, independent of the Al2O3 or TiO2 scaffold. Without a hole-transport layer, non-radiative recombination is strongly enhanced, which reduces the Open-Circuit Voltage. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Michael D. Mcgehee - One of the best experts on this subject based on the ideXlab platform.
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re evaluating the role of sterics and electronic coupling in determining the Open Circuit Voltage of organic solar cells
Advanced Materials, 2013Co-Authors: Kenneth R. Graham, Patrick Erwin, Dennis Nordlund, Koen Vandewal, Guy Olivier Ngongang Ndjawa, Eric T. Hoke, Alberto Salleo, Mark E. Thompson, Michael D. McgeheeAbstract:The effects of sterics and molecular orientation on the Open-Circuit Voltage and absorbance properties of charge-transfer states are explored in model bilayer organic photovoltaics. It is shown that the Open-Circuit Voltage correlates linearly with the charge-transfer state energy and is not significantly influenced by electronic coupling.
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Re‐evaluating the Role of Sterics and Electronic Coupling in Determining the Open‐Circuit Voltage of Organic Solar Cells
Advanced Materials, 2013Co-Authors: Kenneth R. Graham, Patrick Erwin, Dennis Nordlund, Koen Vandewal, Guy Olivier Ngongang Ndjawa, Eric T. Hoke, Alberto Salleo, Mark E. Thompson, Michael D. McgeheeAbstract:The effects of sterics and molecular orientation on the Open-Circuit Voltage and absorbance properties of charge-transfer states are explored in model bilayer organic photovoltaics. It is shown that the Open-Circuit Voltage correlates linearly with the charge-transfer state energy and is not significantly influenced by electronic coupling.
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dependence of band offset and Open Circuit Voltage on the interfacial interaction between tio2 and carboxylated polythiophenes
Journal of Physical Chemistry B, 2006Co-Authors: Shawn R Scully, Michael D. Mcgehee, Christine K Luscombe, Jean M J Frechet, Sean E Shaheen, David S GinleyAbstract:The interface of planar TiO2/polymer photovoltaic cells was modified with two carboxylated polythiophenes having different densities of carboxylic acid groups. Both of the interface modifiers increase the photocurrent of the cells but lower the Open-Circuit Voltage. The work function of the TiO2, measured using a Kelvin probe, increases with increasing density of carboxylic acid groups due to the formation of interfacial dipoles pointing toward the TiO2 surface. The formation of interfacial dipoles results in a shift in the band offset at the TiO2/polymer interface, which explains the decrease in the Open-Circuit Voltage. This work demonstrates that care must be taken when using carboxylic acid side groups to attach polymers to titania surfaces in photovoltaic cells. If the density of attachment groups is just enough to attach the polymer, then the benefits of the interface modifier can be realized without substantially decreasing the Open-Circuit Voltage.
