The biggest obstacle to making use of solar energy has been the excessively high price of solar cells made of inorganic semiconductors. In contrast, solar cells based on semiconducting polymers are affordable, light, thin, and flexible—but their performance has been lacking.
A team led by Chain-Shu Hsu at the National Chaio Tung University and Yuh-Lin Wang at Academia Sinica in Taiwan has now developed a new approach that uses fullerene nanorods to significantly increase the effectiveness of polymer-based solar cells. They introduce their work in the journal Angewandte Chemie.
In the photoactive layer of a solar cell, light energy sets electrons free. This leaves behind positively charged gaps or “holes”. Electrons and holes must be separated quickly and efficiently, or they recombine and reduce the power of the solar cell. The efficiency of a solar cell thus depends on how well the resulting charge is directed away and transported to the electrodes.
In polymer solar cells, it is possible to attain more efficient charge separation through the addition of acceptors, such as fullerenes, which take up electrons. One highly promising concept is to embed the acceptor molecules in a disordered matrix made of photoactive polymer chains. The boundary surface between the two components is thus spread over the entire layer. This construct is known as a “bulk-hetero contact”. After charge separation, the electrons and holes are located in different molecular systems, which transport them selectively to opposite electrodes.
The problem is that the two materials are not evenly distributed. The travel pathways for the charges are thus disordered, allowing holes and electrons to encounter each other easily. In addition, charge-separated islands can occur. The solution would be an “ordered bulk-hetero contact”, a periodic structure of vertically directed, interpenetrating regions of both materials. Electrons and holes would then have straight pathways that do not cross. However, it has previously not been possible to produce any effective photolayer using this principle, because the components are not molecularly intermixed, making the electron pathways too long to produce effective charge separation.
The Taiwanese researchers decided to combine the two structural principles. By using a nano-casting process, they produced a layer of vertically oriented nanorods from a cross-linking polymeric fullerene material. The spaces between the rods were filled with a mixture made from a photoactive polymer and a fullerene. This layer ensures effective charge separation, and the interpenetration of the fullerene nanorods ensures ordered – and thus effective—charge transport. Solar cells made with this novel combined photolayer are stable and achieve amazingly high performance.
Angewandte Chemie International Edition, Permalink to the article: http://dx.doi.org/10.1002/anie.201103782
Chain-Shu Hsu | Angewandte Chemie
Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction