Researchers from North Carolina State University and Hong Kong University of Science and Technology have found that temperature-controlled aggregation in a family of new semi-conducting polymers is the key to creating highly efficient organic solar cells that can be mass produced more cheaply. Their findings also open the door to experimentation with different chemical mixtures that comprise the active layers of the cells.
Polymer solar cells are a delicately controlled mixture of a polymer donor and a fullerene acceptor. The cell is created by adding a solvent to the polymer and fullerene until the mixture becomes a liquid, then spreading the liquid thinly onto a surface.
As the solvent evaporates, the thin layer solidifies, with the donor material hardening into tiny, highly ordered “clumps” that are connected by other, disordered donor molecules, and the acceptor weaving around them. Currently the most efficient organic solar cells are manufactured using one of only two different fullerenes.
NC State physicist Harald Ade and postdoctoral researcher Wei Ma had previously studied the morphology of solar cells and found that the size scale of the clumps within the donor layer and the aggregation – or interaction between neighboring molecules within the layers – were the main drivers of solar cell efficiency.
In a paper published today in Nature Communications, Ade, Ma and a team of chemists from the Hong Kong University of Science and Technology led by He Yan show that size scale and aggregation within these devices are strongly temperature dependent.
They also show that record efficiencies of up to 10.8 percent – as opposed to the currently published 9.8 percent – are achievable with the substitution of numerous fullerenes. Additionally, this performance can be achieved in thick film devices.
“Once we saw how temperature affected the aggregation and morphology of these solar cells, it allowed the chemists more freedom to play with different chemical compositions in the active layer,” Ade says. “Yan’s team demonstrated 10 percent efficiency with 10different mixtures, and in thicker films.
So these solar cells could be compatible with existing methods of mass production, like slot die casting and roll-to-roll processing similar to newspaper printing, rather than the more expensive production methods currently in use that are required for thickness control.
“We hope that these findings will allow others to experiment with different polymer:fullerene blends, further increasing the efficiency of solar cells, decreasing their production costs and leading to a commercially viable alternative source of energy.”
Note to editors: The abstract of the paper follows.
“Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells”
Authors: Yuhang Liu, Jingbo Zhao, Zhengke Li, Cheng Mu, Huawei Hu, Kui Jiang, Haoran Lin, and He Yan, Hong Kong University of Science and Technology; Harald Ade and Wei Ma, North Carolina State University
Published: Online in Nature Communications
Abstract: Although the field of polymer solar cell has seen much progress in device performance in the past few years, several limitations are holding back its further development. For instance, current high-efficiency (>9.0%) cells are restricted to material combinations that are based on limited donor polymers and only one specific fullerene acceptor. Here we report the achievement of high-performance (efficiencies up to 10.8%, fill factors up to 77%) thick-film polymer solar cells for multiple polymer:fullerene combinations via the formation of a near-ideal polymer:fullerene morphology that contains highly crystalline yet reasonably small polymer domains. This morphology is controlled by the temperature-dependent aggregation behavior of the donor polymers and is insensitive to the choice of fullerenes. The uncovered aggregation and design rules yield three high-efficiency (>10%) donor polymers and will allow further synthetic advances and matching of both the polymer and fullerene materials, potentially leading to significantly improved performance and increased design flexibility.
Dr. Harald Ade | EurekAlert!
Additive manufacturing reflects fundamental metallurgical principles to create materials
18.01.2019 | University of Sheffield
Brilliant glow of paint-on semiconductors comes from ornate quantum physics
17.01.2019 | Georgia Institute of Technology
The scientific and political community alike stress the importance of German Antarctic research
Joint Press Release from the BMBF and AWI
The Antarctic is a frigid continent south of the Antarctic Circle, where researchers are the only inhabitants. Despite the hostile conditions, here the Alfred...
World first experiments on sensor that may revolutionise everything from medical devices to unmanned vehicles
The new sensor - capable of detecting vibrations of living cells - may revolutionise everything from medical devices to unmanned vehicles.
Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state.
In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken...
Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing.
It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains:
The phenomenon of so-called superlubricity is known, but so far the explanation at the atomic level has been missing: for example, how does extremely low friction occur in bearings? Researchers from the Fraunhofer Institutes IWM and IWS jointly deciphered a universal mechanism of superlubricity for certain diamond-like carbon layers in combination with organic lubricants. Based on this knowledge, it is now possible to formulate design rules for supra lubricating layer-lubricant combinations. The results are presented in an article in Nature Communications, volume 10.
One of the most important prerequisites for sustainable and environmentally friendly mobility is minimizing friction. Research and industry have been dedicated...
16.01.2019 | Event News
14.01.2019 | Event News
12.12.2018 | Event News
18.01.2019 | Materials Sciences
18.01.2019 | Life Sciences
18.01.2019 | Health and Medicine