A team of researchers from MIT (with support the from Eni-MIT Alliance Solar Frontiers Program and the National Science Foundation) has recently developed a process that prints solar cells onto a fabric or paper substrate. The Youtube video ("Dynamic Folding of a Paper Solar Cell Circuit") looks like something out of a sci-fi movie and is nothing short of impressive (ooh, shiny!). The video demonstrates that the cell is flexible and can be folded without loss of conductivity.
The full research article was published on June 8th, 2011 in Advanced Materials. The abstract description is: “Organic photovoltaic circuits are monolithically fabricated directly on a variety of common paper substrates using oxidative chemical vapor deposition to vapor print conformal conductive polymer electrodes. The paper photovoltaic arrays produce >50 V, power common electronic displays in ambient indoor lighting, and can be tortuously flexed and folded without loss of function".
The Solar Cell Printing Process
The MIT news article, titled “While You're Up, Print Me a Solar Cell” describes the deceptively simple solar cell printing process in more depth.
This process requires five layers of material to be deposited on the same sheet. A paper mask creates the pattern. The team was able to successfully imprint the “ink” on ordinary untreated paper including copy paper, tracing paper, tissue paper and newsprint. They even successfully printed a cell on a sheet of PET plastic (to demonstrate exceptional durability).
Most photovoltaic manufacturing processes require liquids or higher temperatures. This printing process is unique because it occurs in a relatively cold (less than 120°C) vacuum chamber and uses vapors to create the cells.
Costs of Printed Solar Cells
While the solar cell printing process sounds complicated, it's actually a relatively inexpensive process that is commonly used on the commercial scale to produce things like silver potato chip bag liners.
In addition, there is a significant cost benefit because of the materials used in printable solar cells. For conventional solar cells, substrate material and installation costs are typically greater than the cost of the active films of the cells themselves. Since these printed solar cells use paper as a substrate instead of glass, cost savings could be material.
Efficiency of Printed Solar Cells
Currently the cells have an efficiency of only one percent, but the research team believes this would increase significantly with fine-tuning of the materials. While the team did not divulge its efficiency goal for the cells, the current power generation is enough to power something small.
Functions of Printed Solar Cells
While these printed solar cells could function as an “on-chip” for other paper electronics, the most exciting potential for these cells could be integration with items like window shades, awnings, wall coverings, apparel and documents. Who wouldn't want a t-shirt that charges your phone? For outdoor uses, the researchers demonstrated that the paper could be coated with standard lamination materials to protect it from the elements.