From: howard.smith@spacebbs.com (Howard Smith) 
Newsgroups: sci.energy
Subject: New Solar cell
Date: 30 Sep 92 10:34:00 GMT
Distribution: na
Organization: SPACE BBS - Menlo Park, CA - 10 Lines + 4gB - 415-323-4193
Reply-To: howard.smith@spacebbs.com (Howard Smith) 

This message was written by John Gotthold, sysop of the  Hydrogen
BBS,  1-408-738-4014,  2400 baud, 8N1, sponsored by  the  Silicon
Valley chapter of the American Hydrogen Association.

                    LOW COST SOLAR CELL
Last year at Hydrogen 91 in Independence Missouri, An engineer by
the name of Shiller presented a paper on "A Low cost, high  effi-
ciency  solar cell based on  Dye--Sensitized  Colloidal  Titanium
Dioxide  Films.". So here is an update from Electronics  Now  and
Solar Mind.

The  cell uses liquids and is related to a wet cell  battery.  An
electrolyte  of  lithium salt or something similar is  used.  The
upper terminal is a conductive metal film under a layer of  clear
glass. The bottom terminal is also a conductive metal film.  Onto
the  bottom film a very rough and very thin layer of  a  titanium
dioxide semiconductor is deposited. Together they form the  metal
barrier diode. The semiconductor film is made as rough as  possi-
ble to greately increase  its surface area. The present effective
areas are in the 2000/1 range.

A one-molecule thin monolayer of trimetric ruthenium dye then  is
deposited on the semiconductor surface. The single-dye  molecules
can act as both an antenna and a rectifier. An existing  electron
in the electrolyte solution will have its energy level  increased
by the incoming optical photons. These enhanced energy  electrons
jump the semiconductor junction, go through the load,  delivering
useful power, and return via the top electrode, creating a  self-
rectifying  and  light-induced photocurrent.

So  far  the actual efficiencies are only  slightly  better  than
polysilicon  cells.  But  all of the materials  are  far  cheaper
(titanium  dioxide  is used to make white house paint  and  white
toothpaste).  and only small amounts of the dye are  used.  These
cells  also lend themselves to larger area, high volume  process-
ing. {Shiller said you could make a workable cell on your kitchen
table}

There are several remarkable similarities between dye-based solar
and  photosynthesis. In fact the biggest difference is that  dye-
based  photosynthesis stops with its generated  electrons,  while
plant  photosyn- thesis will go on and use the high energy  elec-
trons  to  drive the intermediate chemical reactions,  which  can
ultimately create sugars, cellulose, and other tastey stuff. Dye-
based solar-energy conversion is already more efficient than  the
most  efficient plants known today. On the other hand plants  can
create  and repair themselves. The dye based cells can be  tinted
at the oxide level.

Picture a sky scraper with gold tinted windows shimmering in  the
sun. Every window a solar cell providing all the power the build-
ing  needs  and electrolyzing hydrogen for storage when  the  sun
don't  shine.  This  was invented by a Swiss  professor  and  the
Germans are trying to produce it. Happy Solar Cell windows!!!!
---
 . SLMR 2.1a . We all live in a yellow subroutine.
                                                                                                    
Newsgroups: sci.energy