Transparent Solar Film Gets Big Efficiency Boost

July 30th, 2013 by James Ayre

This article was first published on sister site Green Building Elements.

A novel, transparent, two-layer solar film — possessing an impressive efficiency conversion of 7.3% — has been created by researchers at the University of California–Los Angeles. This is about double the transparent solar cell efficiency the researchers had previously achieved. The solar film can be placed on windows, buildings, sunroofs, electronics displays, etc; harvesting energy while still at the same time allowing light to pass through and visibility/transparency to be maintained.

The new solar film is essentially an improved form of the “breakthrough photovoltaic cell design” that the same researchers unveiled last year — an improved form with nearly double the efficiency, that is. It consists of two thin polymer solar cells that work together to maximize sunlight collection and conversion to electricity — the two cells absorb more light than single-layer solar devices do because together they absorb light from a wider part of the solar spectrum. There’s also a thin layer of ‘novel materials’ present between the two cells that works to reduce energy loss.

transparent solar cell efficiency boosted

“New solar cells. UCLA researchers have developed photovoltaic cells with twice the energy harvesting capacity of cells developed in 2012. The cells, which can be processed to be transparent or in shades ranging from light green to brown, could be used to make building windows, smartphone screens, car sunroofs and other surfaces into sources of sustainable energy.”
Image Credit: Solar Cell, Yang Yang, 2013

The University of California–Los Angeles has more:

The tandem polymer solar cells are made of a photoactive plastic. A single-cell device absorbs only about 40% of the infrared light that passes through. The tandem device — which includes a cell composed of a new infrared-sensitive polymer developed by UCLA researchers — absorbs up to 80% of infrared light plus a small amount of visible light.

While a tandem-structure transparent organic photovoltaic (TOPV) device developed at UCLA in 2012 converts about 4% of the energy it receives from the sun into electric power, the new tandem device — which uses a combination of transparent and semi-transparent cells — achieves a conversion rate of 7.3%.

Researchers say that the new cells could serve as a power-generating layer on windows and smartphone displays without compromising users’ ability to see through the surface. The cells can be produced so that they appear light gray, green or brown, and so can blend with the color and design features of buildings and surfaces.

“Using two solar cells with the new interfacial materials in between produces close to two times the energy we originally observed,” stated Yang Yang, the Carol and Lawrence E. Tannas, Jr, Professor of Engineering at the UCLA Henry Samueli School of Engineering and Applied Science. “We anticipate this device will offer new directions for solar cells, including the creation of solar windows on homes and office buildings.”

The researchers also note that, thanks to the fact that the materials involved can be processed at low temperatures, they are relatively easy to manufacture, as compared to most other solar cell designs. A fact that should help to keep the cost of producing them relatively low.

It all sounds pretty good. This sort of solar cell sounds like a good fit for dense urban areas, where economy of space is an important factor in decisions concerning solar energy. And as we’ve reported before, solar-skinned buildings are becoming increasingly common and should continue to do so well into the future — leaving lots of room for new transparent solar cell designs.

The new research was funded primarily by the Air Force Office of Scientific Research, the Office of Naval Research, and EFL Tech. The new research was published online July 26th in the Royal Society of Chemistry journal Energy & Environmental Science.

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Tags: see-through solar cells, see-through solar film, tandem-structure transparent organic photovoltaic, TOPV solar energy, transparent solar cells, Transparent solar film, UCLA Henry Samueli School of Engineering and Applied Science, UCLA transparent solar cells doubled efficiency

About the Author

James Ayre 's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.

Steeple

What are the issues involved in having electric current flowing from a disparate sources such as windows, building skins, etc…? Just thinking that there might be some safety issues or even potential corrosion issues from current flowing outside of traditional electric circuitry. Appreciate any insight here.
- Matthew Crane
  
  There should be no issues here. The current is entirely contained in the device, which could be directly contacted by leads, and is likely to be encapsulated (for lifetime issues) in it’s final form. Corrosion on the building simply won’t happen.
  
  In this case the electrodes are made of tin-doped indium oxide (ITO), Ag nanowires, and a conductive polymer (PFN).
  - Steeple
    
    Thanks for that, Matthew
Marion Meads

Let us hope it works very well with diffused light and not require direct sunlight.
- Wayne Williamson
  
  Marion, it looks like to me it would be more in the range of 73 Watts/m2 in full sun…
- Matthew Crane
  
  OPV tends to hold up well in installed conditions: heat (due to thermalization or environment) improves performance, compared with inorganic technologies, where it inhibits efficiencies. In addition, it is strongly capable of high absorption of diffuse light.
  
  Very nice article on costs of OPV technology. This analysis on a 7% efficiency device with ~5 year lifetime suggests a levelized energy cost of between 0.25 and 0.66 $/kW-hr. But, this is only for a single junction cell and assumes a solar field installation size. Interestingly, most of the cost stems from the substrate. If this could be alleviated, a lot of this technology would be close or immediately economically viable.
  
  “Economic assessment of solar electricity production from organic-based photovoltaic modules in a domestic environment”