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Research and Innovation

New Materials Yield Record Efficiency Polymer Solar Cells

For Immediate Release

Harald Ade

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.

Temperature-controlled aggregation in a family of new semi-conducting polymers appear to be the  key to creating highly efficient organic solar cells that can be mass produced more cheaply.
Temperature-controlled aggregation in a family of new semi-conducting polymers appears to be the key to creating highly efficient organic solar cells that can be mass produced more cheaply.

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

DOI:  10.1038/ncomms6293

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.

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  1. Hello sir
    I am planning to work on organic solar cells. Please suggest me some new organic material for that.
    Thank you

  2. Sir..

    I am Dennish Babu from India.

    I am started my work on Polymer based solar cells.

    How can i find the either n-type or p-type polymer conductor ? In which method i have to use for it?.

    Can you tell me sir?.

    Dennish Babu

    1. Hi, P3HT (Poly (3-Hexylthiophene)) is a famous donor, and PCBM (Phenyl-C61-butyric acid a kind of fullerene) is a famous acceptor. you should solve them like the report says “then spreading the liquid thinly onto a surface. As the solvent evaporates, the thin layer solidifies” on a surface that already has some layers, put other layers on them and there’s a lot of other stuff that I don’t know. good luck

  3. That’s a nice piece of work BUT this press release gives the impression that efficiencies had been achieved on the solar cells shown on the photograph.
    –> This whole story is therefore misleading <–

    The scientific publication does not even mention any performed R2R fabrication with these materials or measurements of cells shown in the photograph. All results have been been achieved on spin coated devices with evaporated electrodes on glass. The area is tiny with around 5 square millimeter.

    !!! NO results are given for the R2R device !!! (why? are they simply too bad or would they not attract media feedback) Please report real data on actual useful device sizes.