Small-scale polymer solar cell with a conversion efficiency of 11.5% eclipses previous best

29-Jul-14

A small-scale polymer solar cell with a conversion efficiency of 11.5% has been developed by a research team in USA – eclipsing the previous best of 10.6% set by the same team but lower than the 12% mark with small-molecule organic technology set by Heliatek last year. Yang Yang’s research group at the University of California, Los Angeles (UCLA) improved the performance of its earlier tandem cell by incorporating an additional junction. The new triple-junction design is similar in principle to the high-efficiency multi-junction cells used to power satellites, and is considered by the team to be the best demonstration so far of such technology with organic material. UCLA graduate student Johnny (Chun-Chao) Chen said: “Our work is not the first demonstration of a triple-junction polymer cell, but it should be considered as the first ‘successful’ demonstration.” That is because earlier demonstrations have disregarded important features such as optical interference in triple-junction designs, and the suitability of interconnecting layers. Following detailed analysis of each sub-cell inside the triple-junction polymer cell and extensive optical simulation work, the UCLA team were able to optimize the photocurrent gain with virtually no voltage loss – the key to improving the cell’s efficiency to 11.5%. In terms of potential commercialization, Chen says that the group – which collaborates with Sumitomo Chemical on materials development - is open to other licensing partners. In the meantime, further work will focus on reaching higher efficiencies and introducing the triple-junction concept to developers of other novel solar cells, for example in hybrid cell designs incorporating perovskite and CIGS materials.