Solar Cell Energy Conversion Efficiency
This photo of Bell Telephone Labs' three scientists, G.L. Pearson, D.M. Chapin,
and C.S. Fuller, inventors of the "Bell Solar Battery," reminds me of the very
familiar shot of John Bardeen, Walter Brattain, and William Shockley huddled over
point contact transistor in December of 1948. The "battery" terminology is an
interesting choice since we normally think of a battery as a charge storage device,
but in fact a battery is fundamentally a charge creation device. A
may be recharged by reversing the depleted chemical (or other) process that generated
the initial charge, but it first created the potential via a basic charge separation
process. What we today refer to as a solar cell is a form of
primary battery that is
not rechargeable. Just as some chemical batteries (cells) are reactivated by replenishing
the electrolyte, the solar cell is replenished by photons giving up their energy
to the semiconductor substrate. At the time of this advertisement (1954), a 6% efficiency
for silicon solar cells was considered to be breakthrough compared to the germanium
type used previously. Today's solar cells whose substrates are complex compounds
of various elements, have yielded as high as nearly 50% energy conversion efficiency.
We've come a long
Bell Telephone Laboratories Solar Battery Ad
The Bell Solar Battery. A square yard of
the small silicon wafers turns sunshine into 50 watts of electricity. The battery's
6% efficiency approaches that of gasoline and steam engines and will be increased.
Theoretically the battery will never wear out. It is still in the early experimental
Bell Solar Battery
Bell Laboratories scientists have created the Bell Solar Battery. It marks a
big step forward in converting the sun's energy directly and efficiently into usable
amounts of electricity. It is made of highly purified silicon, which comes from
sand, one of the commonest materials on earth.
The battery grew out of the same long-range research at Bell Laboratories that
created the transistor - a pea-sized amplifier originally made of the semiconductor
germanium. Research into semiconductors pointed to silicon as a solar energy converter.
Transistor-inspired techniques developed a silicon wafer with unique properties.
The silicon wafers can turn sunlight into electricity to operate low-power mobile
telephones, and charge storage batteries in remote places for rural telephone service.
These are but two of the many applications foreseen for telephony.
Thus, again fundamental research at Bell Telephone Laboratories paves the way
for still better low-cost telephone service.
Inventors of the Bell Solar Battery, left to right, C. L. Pearson, D. M. Chapin
and C. S. Fuller - checking silicon wafers on which a layer of boron less than 1/10,000
of an inch thick has been deposited. The boron forms a "p-n junction" in the silicon.
Action of light on junction excites current flow.
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Posted June 9, 2020