SPEAKER:
Dr He Yan (Henry) obtained his PhD in Chemistry from Northwestern University with Professor Tobin Marks. Dr Yan then spent most of his research career at Polyera Corporation, a leading company in the Organic Electronics industry. Between 2006 to 2012, Dr Yan led Polyera’s research projects in organic semiconductor and solar cell materials. In 2009, Dr Yan and his team published the first high-mobility n-type semiconducting polymer in Nature and the work was referred to as the “new transistor age” on the cover page of Nature.
With these achievements, Dr Yan was invited to receive the IdTechEx Printed Electronics “Best Organic Material” award in Dresden, Germany in 2010. In 2012, Dr Yan joined Hong Kong University of Science and Technology and started a new research group focusing on organic solar cells. Recently, Dr Yan’s group achieved multiple cases of polymer solar cells efficiencies between 10-11.5%. The achievement of a record efficiency of 11.5% has been officially certified and is noted as a technological breakthrough in the renowned NREL chart of “best research-cell efficiencies.”
ABSTRACT:
Polymer solar cell (PSC) technology has attracted much attention due to its promise as low-cost conversion of solar energy. Despite recent progress, several limitations are holding back PSC development. For instance, current high-efficiency (>9.0%) PSCs{Liao, 2013 #103} are restricted to materials combinations that are based on limited donor polymers and only one specific fullerene acceptor, PC71BM. Furthermore, best-efficiency PSCs are mostly based on relatively thin (100 nm) active layers. Thick-film PSCs generally exhibit lower fill factors and efficiencies compared to the best thin-film PSCs. Here we report multiple cases of high-performance thick-film (300 nm) PSCs (efficiencies up to 10.8%, fill factors up to 77%) based on conventional PCBM and many non-PCBM fullerenes. Our simple aggregation control and materials design rules allowed us to develop, within a short time, three new donor polymer, six fullerenes (including C60-based fullerenes), and over ten polymer:fullerene combinations, all of which yielded higher efficiency than previous state of art devices (~9.5%).
The common structural feature of the three new donor polymers, the 2-octyldodecyl (2OD) alkyl chains sitting on quaterthiophene, causes a temperature-dependent aggregation behavior that allows for the processing of the polymer solutions at moderately elevated temperature, and more importantly, controlled aggregation and strong crystallization of the polymer during the film cooling and drying process. This results in a well-controlled and near-ideal polymer:fullerene morphology (containing highly crystalline, preferentially orientated, yet small polymer domains) that is controlled by polymer aggregation during warm casting and thus insensitive to the choice of fullerenes. Following this strategy, a new record PSC efficiency of 11.5% (certified by Newport) was recently achieved in our group, which has been included as a major milestone for organic solar cells in the “best research efficiency chart” by NREL.
Reference:
- Liu, Y., Zhao, J., Li, Z., Mu, C., Ma, W., Hu, H., Jiang, K., Lin, H., Ade, H. and Yan, H., “Aggregation and morphology control enables multiple cases of high-efficiency polymer solar cells.” Nat. Commun., 5, 5293, (2014).
- Yan, H.; Chen, Z.; Zheng, Y.; Newman, C.; Quinn, J.; Dotz, F.; Kastler, M.; Facchetti, A. “A high-mobility electron-transporting polymer for printed transistors.” Nature，(2009), 457(7230), 679-686.