ABSTRACT
The first observation of the photovoltaic effect was made by
Alexander-Edmund Becquerel in 1839. The effect was observed
later in many different forms with different materials. However
the conversion of solar energy into electrical energy with these
structures and devices never got above 1% until the 1950s. John
Shive of the Bell Telephone Laboratories (BTL) in 1952 reported on
a grown p-n junction photocell of silicon that used the very small
area of the region where the junction came to the surface of the
crystal. It was not thought of as a power device but as a sensor. In
1953, Daryl Chapin (an electrical engineer) was looking for a power
source to replace batteries that operated remote communication
systems. Once such source was a thermopile heated by burning a gas
such as propane. At the same time Gerald Pearson (a physicist) and
Calvin Fuller (a chemist) were investigation large area p-n junction
structures for power rectifiers. Fuller studied the diffusion of lithium
at moderate temperatures (∼500◦C) into silicon to form a large area junction and Pearson would contact the two sides of the diffused
wafer and observed that the resulting device was very sensitive to
light. However this device changed its electrical characteristics in
time due to the rapid diffusion of lithium into the silicon even at
room temperature. Fuller then initiated the study of boron diffusion
into n-type silicon, which required a much higher temperature
(∼1000◦C) and the resulting p-n junction was stable at room temperature. When Pearson made the measurements in sunlight
and observed the photovoltaic effect, he calledme into his laboratory
towitness this observation (in December 1953). Pearson recognized
the importance of this development and three of them (Chapin,
Fuller and Pearson) worked together to improve the characteristics
of the device for solar energy conversion and published their
important letter in the Journal of Applied Physics in May 1954, where they reported a conversion efficiency of approximately 6%.
In February 1954, I was asked to take that boron-diffused device,
optimize it and make it reproducible so that it could be used for
some demonstrations. Twomonths later, I and my technologists had
assembled sufficient cells to demonstrate these Bell Solar Batteries
(as they were called) at Murray Hill New Jersey (the location of
the BTL) and a couple of days later at the National Academy of
Sciences in Washington, DC. in a public announcement. During the
next few months I performed some calculations and analysis of
experimental data that I had accumulated and submitted a paper
that was published in the Journal of Applied Physics in May 1955, pointing out that the series resistance of the device was the most
important parameter to control as well as showing that the energy
band-gap of the semiconductor material determines the maximum
efficiency that might be expected from such materials. Silicon was
near the maximum of this curve. Carl Frosch and his team improved
upon Fuller’s diffusion technique, which permitted us to diffuse
several large slices of silicon simultaneously. By mid-1955, we were
able to make 8% to 9% efficient cells, which we reported at the
Conference on the Use of Solar Energy held in Tucson and Phoenix,
Arizona in November 1955. Later that year, Ed Stansbury of the BTL
was able to make an 11% efficient small cell. The first application
of these silicon solar cells was their use in a telephone application in
Americus, Georgia, where a trial was held for sixmonths in late 1955
and early 1956. Even though the results of the trial were successful
from a technology point of view, no further use was made in the Bell
system at that time due to cost considerations.
