Research Partners Develop Semitransparent Organic Solar Cells

Semitransparent organic solar cells could be used to transform regular window glazing into a window that generates electrical power while retaining its basic functionality.

GPEC, a developer of Organic Photovoltaic (OPV) technology for ultra-low cost, high power solar cells, says this latest achievement is part of its overall R&D efforts to increase the operating performance of its OPV technology and develop insight into application areas. The company's partner researchers detailed their work in the June 5, 2006 issue of Applied Physics Letters.

Traditionally, PV or "solar" cells have been constructed of an inorganic semiconductor like silicon. Efficient silicon-based devices, especially of large surface area, are difficult and expensive to produce. Silicon cells are fragile, heavy and opaque -- limiting applications and potential uses. Cost is a critical factor in the solar cell industry as solar-generated power is still four to six times more expensive to consumers than coal-generated power, states the release.

Recent efforts have focused on the use of "organic" semiconductor materials. Organic semiconductors contain the ubiquitous element Carbon and have the potential to achieve ultra-low-cost production costs and high power output in solar cells. Organic solar cells are ultra-thin, flexible and can be applied to large areas including curved or spherical surfaces. Because the organic layers are so thin, semitransparent solar cells can be fabricated creating power-generating windows that retain a significant portion of their basic transparency.

GPEC sponsored researchers at USC, Princeton and Michigan, led by Professor Stephen R. Forrest at Michigan and Professor Mark E. Thompson at USC, have focused on organic "small-molecule" devices that are assembled literally a molecule at a time in highly efficient nanostructures.

Solar cells manufacturers typically use various techniques for trapping incoming light inside the device so that power output can be improved. The typical silicon solar cell is more than 200 microns thick and opaque to visible light. Reflective back contacts are used in thinner thin-film solar cells to increase the absorption of incoming light in the device. Semitransparent cells, because they let some light pass through them, have reduced power output.

In this recent work, GPEC partner researchers at USC, Princeton and Michigan developed semitransparent organic solar cells that leverage the superior absorption capabilities of organic semiconductor materials and nanometer-scale films to achieve high levels of visible light transparency while at the same time minimizing power loss.

"This demonstrates one of the exciting capabilities of organic solar cells," said Aaron L. Wadell, Chief Operating Officer of Global Photonic Energy Corporation. "Because of their strong absorption characteristics and very thin layers, we can build windows that generate electricity while retaining their basic functionality -- that is, they are still windows."