C L A S S N O T E S
Carol Chin ’85
RASPBERRIES, SUNSHINE AND SOLAR CELLS
B Written by STEPHANIE L. GRAHAM
ottom line: The world’s population uses a lot of energy. It’s time to seriously start thinking about alternatives. Let’s think raspberries. In order to understand this line of thinking, one must have
attended chemistry Professor Hal Van Ryswyk’s Alumni Weekend presentation about Creating Your Own Solar Cell. I’ll get to the rasp- berries in a moment. One obvious power alternative is solar energy, which is more in-
cident upon the earth’s surface in one hour than humankind uses in a year. Photovoltaics, a class of solar energy conversion technology producing direct-current electricity from sunlight, is an option, but currently a costly one (Read about PV pioneer Mark Mrohs ’74 on page 22.). Van Ryswyk suggests that the dye-sensitized solar cell (DSSC) is a better, more economical model. They utilize a cheap, rug- ged semiconductor as a lattice upon which low-cost dyes are che- misorbed. A group of about 25 alumni trekked to the chemistry lab to as-
semble their very own solar cell made up of three main components: a semiconductor photoanode lattice that supports the dye and pro- vides a pathway for transport of the high-energy electrons; light-
absorbing dye that injects the high-energy electrons into the semiconductor; and the electrolyte that transports the low-energy electrons from the cathode in the back of the cell to the dye for dye regeneration. Enter the raspberries. Instead of using state-of-the-art DSSC dyes, the
group used anthocyanins–nature’s sunscreen for plants–as the light-absorb- ing dye. This required enthusiastic mashing of raspberries, blackberries and/ or blueberries to extract the juice used on the TiO2
coating. Van Ryswyk described the event as “a typical lab for HMC chemists—ordered
chaos with a lot of fun and some learning mixed in.” Participants–including Ed Fey ’70 (“big blueberry fan”), Carol Chin
’85, Kevin Swartzlander ’08, Robert Luke ’65, Laveille Voss ’85 and Greg Felton ’85–met with varying degrees of success. Van Ryswyk said, “We achieved anywhere from 300 to 400 mV of open
circuit photovoltage (V_oc) and 80 to 300 microamps of short circuit photocur- rent (J_sc). The better overall conversion efficiencies (sunlight to electricity) we saw were 0.15%.” It can be confidently proclaimed that a good time was had by all. Kathy
French ’97 remarked, “It was fascinating, hands-on fun with a practical ap- plication.”
S UMME R 2 0 1 0 H a r v e y Mu d d C o l l e g e
2 9
Ed Fey ’70 and Kevin S
wartzl
Jo and er ’08
hn
Stimson ’94, Prof. Hal Van R
yswyk and Andy Lange ’90
K
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VIN B
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