Photovoltaics continues to be an expensive technology. Dye-based solar cells may represent a more cost-effective alternative to traditional solar cells. In these cells, a dye is used in place of a semiconductor to trap the light.
Tandem cells consisting of both a conventional n-type and an “inverse” p-type dye-sensitized solar cell seem to be especially promising. In the journal Angewandte Chemie, a team of Australian and German scientists has now reported a significant increase in the degree of efficiency of p-type dye-sensitized solar cells through use of an electrolyte based on a cobalt complex.
Conventional n-type dye-sensitized solar cells use a photoanode, a positive electrode coated with an n-type semiconductor, such as titanium dioxide, and a dye. When light strikes the electrode, the dye molecules become excited and release electrons—negative charges, hence the n in n-type—and “inject” them into the n-type semiconductor.
The redox mediator, a component of the electrolyte that can move freely between the electrodes, regenerates the dye by resupplying it with electrons from the counter electrode. In a p-type cell, the process is reversed: a special dye and a p-type semiconductor are located on a photocathode.
The light-activated dye “sucks” electrons out of the valence band of a p-type semiconductor such as nickel oxide. This effectively transfers “electron holes”—positive charges, hence the p in p-type—from the dye. The redox mediator takes the electrons from the dye and hands them over to the counter electrode.
A very promising approach for increasing the performance of photovoltaic cells is to combine both an n-type and a p-type dye-sensitized solar cell to make a tandem cell. However, despite some progress, the performance of the p-type cells still significantly lags behind that of their n-type counterparts. An international team of researchers from Monash University and the Commonwealth Scientific and Industrial Research Organization (Australia), as well as the University of Ulm (Germany), have now achieved a considerable improvement in the efficiency of p-type cells by choosing a different redox mediator.
Researchers working with Udo Bach and Leone Spiccia replaced the previous, commonly used iodide and triiodide system with a well-known cobalt complex, tris(ethylenediamine)cobalt(II)/(III), in which the cobalt can switch between the +2 and +3 oxidation states. The advantage of this system is that the redox potential is significantly lower. As a result, the open-circuit voltage, a critical parameter for solar cells, is doubled and there is still a high enough driving force to ensure rapid and efficient regeneration of the spent dye.These devices achieve an energy-conversion efficiency of 1.3 %, while previous systems attained a maximum of only 0.41 %. The p-type dye-sensitized solar cell with the cobalt-based redox mediator even gave promising performance data under diffuse sunlight experienced on cloudy days.
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201206219
Udo Bach | Angewandte Chemie
Staying in Shape
16.08.2018 | Max-Planck-Institut für molekulare Zellbiologie und Genetik
Chips, light and coding moves the front line in beating bacteria
16.08.2018 | Okinawa Institute of Science and Technology (OIST) Graduate University
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur
What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...
08.08.2018 | Event News
27.07.2018 | Event News
25.07.2018 | Event News
16.08.2018 | Life Sciences
16.08.2018 | Earth Sciences
16.08.2018 | Life Sciences