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Principle Behind Stained Glass Colors Solar Future Bright

Century old stained glass window in Barcelona, Catalonia, Spain
Century old stained glass window in Barcelona, Catalonia, Spain

Researchers from the FOM Institute AMOLF in the Netherlands and Caltech recently made a breakthrough in solar power, by drawing inspiration from stained glass.

For centuries, cathedrals and castles were adorned with stained glass windows whose colors mesmerized worshippers and adorers with their vivid hues that did not fade with time.  These works of art were created back in the late Medieval period when they had no access to dyed plastic.  The dyes of their time evaporated in the thousand degree temperatures needed to form silica into glass.  So the question is, how did they color the glass?  The glass was infused with metallic powder while the glass was still molten.

Metal you say?  Metals have an electronic “fluid” on their surface, composed of plasmons, that interacts with light.  It reflects some of the light, but allows some light to pass through.  That is why fine particles of gold in glass gives the glass a wine red color, because it allows red to pass through.  As a side benefit, some of the light is captured and turned into electricity.  But since the metal particles in stained glass were encased in non-conducting glass, the effect was not realized until recently.  It was examined by scientists at the Lawrence Livermore National Laboratory and the University of California in Davis which tried placing nanoscale “pillars” on the surface of the metal to take advantage of the plasmonic effect.

The scientists from AMOLF and Caltech took a different approach.  Instead of trying to make pillars, they instead made a circuit made out of a film of gold through which they drilled nano sized holes.  Also, they found that by passing light of a particular wavelength through the circuit, electricity could be generated and the charge depended on the wavelength of the light.  In layman’s terms, if they passed blue light through the circuit, they got a negative charge and when red light was shone on it, they got a positive charge.  By varying the spacing between the holes in the circuit, they could get a part that will be charged positively and another that is charged negatively.

But then the material begs the question, if you use gold, isn’t it bound to be expensive?

The foundational research done at Caltech and AMOLF is setting the stage for research in other metals that could do better than gold if not on cost, at least on efficiency.  For example, modern stained glass masters are using copper over gold to get their ruby red glass.

Combining the plasmoelectric effects with current photovoltaic technology can allow us to maximize photovoltaic efficiency of future solar cells.   If so, I can say that the future for solar power is getting beautifully brighter, so much so that it is mesmerizing.

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