Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing

• Published in: Science (American Association for the Advancement of Science) Vol. 317; no. 5835; pp. 222 - 225
• Main Authors: Kim, Jin Young, Lee, Kwanghee, Coates, Nelson E, Moses, Daniel, Nguyen, Thuc-Quyen, Dante, Mark, Heeger, Alan J
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 13.07.2007; The American Association for the Advancement of Science
• Subjects: Absorption spectra; Applied sciences; Architecture; Banded structure; Composite materials; Conversion; Derivatives; Electric current; Energy; Exact sciences and technology; Heterojunctions; Illumination; Luminous intensity; Materials; Materials science; Natural energy; Photovoltaic cells; Photovoltaic conversion; Polymers; Power efficiency; Solar cells; Solar cells. Photoelectrochemical cells; Solar energy; Titanium oxides; Tandem solar cell; Semiconductor materials; Voltage current curve; Transition element compounds; Charge separation; Polymer; Composite material; Absorption spectrum; Inorganic compound; Illumination; Titanium oxide; Current density; Heterostructures
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1141711

Tandem solar cells, in which two solar cells with different absorption characteristics are linked to use a wider range of the solar spectrum, were fabricated with each layer processed from solution with the use of bulk heterojunction materials comprising semiconducting polymers and fullerene derivatives. A transparent titanium oxide (TiOx) layer separates and connects the front cell and the back cell. The TiOx layer serves as an electron transport and collecting layer for the first cell and as a stable foundation that enables the fabrication of the second cell to complete the tandem cell architecture. We use an inverted structure with the low band-gap polymer-fullerene composite as the charge-separating layer in the front cell and the high band-gap polymer composite as that in the back cell. Power-conversion efficiencies of more than 6% were achieved at illuminations of 200 milliwatts per square centimeter.