Nano-Mesh Boosts Organic Solar Cell Efficiency

Princeton University researchers have discovered a cheap and easy way to substantially boost the efficiency of organic solar cells by creating a 'black hole for light'.

Princeton University researchers have discovered a cheap and easy way to substantially boost the efficiency of organic solar cells by creating a ‘black hole for light’, a development that may also have applications for silicon-based solar cells.
   
While cheap to produce and non-toxic, organic solar cells have continued to lag behind their silicon based counterparts in terms of efficiency – but Princeton’s development may be a game-changer.
   
The researchers created a nanostructured “sandwich” of metal and plastic that collects and traps light. In direct sunlight, the souped-up cells only reflect around 4 percent of light and absorb as much as 96 percent. In indirect or diffuse sunlight performance is even better; leading to an overall 175 percent total increase in efficiency.
   
The top layer uses a fine metal mesh just 30 nanometers thick, with apertures 175 nanometers in diameter and 25 nanometers apart. A nanometer is around one hundred-thousandth the width of a human hair. This mesh overlays the semiconducting material and beneath that is the same metal film used in conventional solar cells.
  
The team, led by electrical engineer Stephen Chou, calls the system a “plasmonic cavity with subwavelength hole array” (PlaCSH) and it can be manufactured in wallpaper-sized sheets using a nanoimprint process; a low-cost nanofabrication technique developed by Chou 16 years ago.
   
As well as substantially improving cell efficiency,  PlaCSH also does away with ITO (Indium Tin Oxide) electrodes – the most expensive part of most current organic solar cells.
   
The technology could also reduce the thickness of the silicon used in traditional solar panels by a thousand-fold, substantially reducing manufacturing costs and allowing silicon solar panels to become more flexible.
  
The team is continuing the research, supported in part by the Defense Advanced Research Projects Agency, the Office of Naval Research and the National Science Foundation.
   
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