A "photoelectrochemical cell" is one of two distinct classes of device. The first produces electrical energy similarly to a dye-sensitized photovoltaic cell, which meets the standard definition of a photovoltaic cell. The second is a photoelectrolytic cell, that is, a device which uses light incident on a photosensitizer, semiconductor, or aqueous metal immersed in an electrolytic solution to directly cause a chemical reaction, for example to produce hydrogen via the electrolysis of water.
Artificial photosynthesis is a chemical process that biomimics the natural process of photosynthesis. The term artificial photosynthesis is used loosely, refer to any scheme for capturing and storing energy from sunlight by producing a fuel, specifically a solar fuel. An advantage of artificial photosynthesis is that the solar energy can be immediately converted and stored. By contrast, using photovoltaic cells, sunlight is converted into electricity and then converted again into chemical energy for storage, with some necessary losses of energy associated with the second conversion. The byproducts of these reactions are environmentally friendly. Artificially photosynthesized fuel would be a carbon-neutral source of energy, which could be used for transportation or homes. The economics of artificial photosynthesis are not competitive.
In chemistry, photocatalysis is the acceleration of a photoreaction in the presence of a photocatalyst, the excited state of which "repeatedly interacts with the reaction partners forming reaction intermediates and regenerates itself after each cycle of such interactions." In many cases, the catalyst is a solid that upon irradiation with UV- or visible light generates electron–hole pairs that generate free radicals. Photocatalysts belong to three main groups; heterogeneous, homogeneous, and plasmonic antenna-reactor catalysts. The use of each catalysts depends on the preferred application and required catalysis reaction.
A dye-sensitized solar cell is a low-cost solar cell belonging to the group of thin film solar cells. It is based on a semiconductor formed between a photo-sensitized anode and an electrolyte, a photoelectrochemical system. The modern version of a dye solar cell, also known as the Grätzel cell, was originally co-invented in 1988 by Brian O'Regan and Michael Grätzel at UC Berkeley and this work was later developed by the aforementioned scientists at the École Polytechnique Fédérale de Lausanne (EPFL) until the publication of the first high efficiency DSSC in 1991. Michael Grätzel has been awarded the 2010 Millennium Technology Prize for this invention.
The photovoltaic effect is the generation of voltage and electric current in a material upon exposure to light. It is a physical phenomenon.
A solar cell or photovoltaic cell is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect. It is a form of photoelectric cell, a device whose electrical characteristics vary when it is exposed to light. Individual solar cell devices are often the electrical building blocks of photovoltaic modules, known colloquially as "solar panels". The common single-junction silicon solar cell can produce a maximum open-circuit voltage of approximately 0.5 to 0.6 volts.
Hybrid solar cells combine advantages of both organic and inorganic semiconductors. Hybrid photovoltaics have organic materials that consist of conjugated polymers that absorb light as the donor and transport holes. Inorganic materials in hybrid cells are used as the acceptor and electron transporter in the structure. The hybrid photovoltaic devices have a potential for not only low-cost by roll-to-roll processing but also for scalable solar power conversion.
A quantum dot solar cell (QDSC) is a solar cell design that uses quantum dots as the captivating photovoltaic material. It attempts to replace bulk materials such as silicon, copper indium gallium selenide (CIGS) or cadmium telluride (CdTe). Quantum dots have bandgaps that are adjustable across a wide range of energy levels by changing their size. In bulk materials, the bandgap is fixed by the choice of material(s). This property makes quantum dots attractive for multi-junction solar cells, where a variety of materials are used to improve efficiency by harvesting multiple portions of the solar spectrum.
Heinz Gerischer was a German chemist who specialized in electrochemistry. He was the thesis advisor of future Nobel laureate Gerhard Ertl.
Organic photovoltaic devices (OPVs) are fabricated from thin films of organic semiconductors, such as polymers and small-molecule compounds, and are typically on the order of 100 nm thick. Because polymer based OPVs can be made using a coating process such as spin coating or inkjet printing, they are an attractive option for inexpensively covering large areas as well as flexible plastic surfaces. A promising low cost alternative to conventional solar cells made of crystalline silicon, there is a large amount of research being dedicated throughout industry and academia towards developing OPVs and increasing their power conversion efficiency.
Photoelectrochemical processes are processes in photoelectrochemistry; they usually involve transforming light into other forms of energy. These processes apply to photochemistry, optically pumped lasers, sensitized solar cells, luminescence, and photochromism.
Nanocrystal solar cells are solar cells based on a substrate with a coating of nanocrystals. The nanocrystals are typically based on silicon, CdTe or CIGS and the substrates are generally silicon or various organic conductors. Quantum dot solar cells are a variant of this approach which take advantage of quantum mechanical effects to extract further performance. Dye-sensitized solar cells are another related approach, but in this case the nano-structuring is a part of the substrate.
Photoelectrochemical reduction of carbon dioxide, also known as photoelectrolysis of carbon dioxide, is a chemical process whereby carbon dioxide is reduced to carbon monoxide or hydrocarbons by the energy of incident light. This process requires catalysts, most of which are semiconducting materials. The feasibility of this chemical reaction was first theorised by Giacomo Luigi Ciamician, an Italian photochemist. Already in 1912 he stated that "[b]y using suitable catalyzers, it should be possible to transform the mixture of water and carbon dioxide into oxygen and methane, or to cause other endo-energetic processes."
A solar fuel is a synthetic chemical fuel produced from solar energy. Solar fuels can be produced through photochemical, photobiological, and electrochemical reactions.
Adam Heller is an Israeli American scientist and engineer. He is Chief Science Officer of SynAgile Corp. of Wilson, Wyoming, consults to Abbott Diabetes Care of Alameda, California, and is Ernest Cockrell Sr. Chair Emeritus of Engineering at The University of Texas at Austin. His 1973 paper with James J. Auborn established the feasibility of high energy density, high-voltage, non-rechargeable lithium batteries. Their 3.6-volt lithium thionyl chloride and 3.7-volt lithium sulfuryl chloride batteries remain in use in applications requiring very high energy density and a shelf life of 20 years or more.
Biological photovoltaics, also called biophotovoltaics or BPV, is an energy-generating technology which uses oxygenic photoautotrophic organisms, or fractions thereof, to harvest light energy and produce electrical power. Biological photovoltaic devices are a type of biological electrochemical system, or microbial fuel cell, and are sometimes also called photo-microbial fuel cells or “living solar cells”. In a biological photovoltaic system, electrons generated by photolysis of water are transferred to an anode. A relatively high-potential reaction takes place at the cathode, and the resulting potential difference drives current through an external circuit to do useful work. It is hoped that using a living organism as the light harvesting material, will make biological photovoltaics a cost-effective alternative to synthetic light-energy-transduction technologies such as silicon-based photovoltaics.
Quantum photoelectrochemistry is the investigation of the quantum mechanical nature of photoelectrochemistry, the subfield of study within physical chemistry concerned with the interaction of light with electrochemical systems, typically through the application of quantum chemical calculations. Quantum photoelectrochemistry provides an expansion of quantum electrochemistry to processes involving also the interaction with light (photons). It therefore also includes essential elements of photochemistry. Key aspects of quantum photoelectrochemistry are calculations of optical excitations, photoinduced electron and energy transfer processes, excited state evolution, as well as interfacial charge separation and charge transport in nanoscale energy conversion systems.
A solaristor is a compact two-terminal self-powered phototransistor. The two-in-one transistor plus solar cell achieves the high-low current modulation by a memresistive effect in the flow of photogenerated carriers. The term was coined by Dr Amador Perez-Tomas working in collaboration with other ICN2 researchers in 2018 when they demonstrated the concept in a ferroelectric-oxide/organic bulk heterojunction solar cell.
In semiconductor physics, the flat band potential of a semiconductor defines the potential at which there is no depletion layer at the junction between a semiconductor and an electrolyte or p-n-junction. This is a consequence of the condition that the redox Fermi level of the electrolyte must be equal to the Fermi level of the semiconductor and therefore preventing any band bending of the conduction and valence band. An application of the flat band potential can be found in the determining the width of the space charge region in a semiconductor-electrolyte junction. Furthermore, it is used in the Mott-Schottky equation to determine the capacitance of the semiconductor-electrolyte junction and plays a role in the photocurrent of a photoelectrochemical cell. The value of the flat band potential depends on many factors, such as the material, pH and crystal structure of the material
Krishnan Rajeshwar is a chemist, researcher and academic. He is a Distinguished University Professor and Founding Director of the Center for Renewable Energy Science & Technology at The University of Texas at Arlington.
Figure 1(a) band diagram of n-type semiconductor/liquid junction
Figure 1(b) band diagram of p-type semiconductor/liquid junction
