Panasonic
Solar Cells Handbook, Page 4
August 1998
THIN-FILM SOLAR CELLS (SUNCERAM II) - CONTINUED
3. Easily accommodated by high-voltage equipment
A printing method is used for the entire film-forming
process of the Sunceram II, with the result that solar
cells with the desired high voltage can be formed very
densely and thinly on a single substrate. This, in turn,
fulfills the need for cells with various voltages.
4. Easy increase in surface area
The
printing and sintering methods used enable a
uniform film to be produced, which means that it is
easier to
increase the surface area of each cell than with
crystalline silicon. It also means that it is possible to
produce any shape of cell with relative ease.
1.5.
Output characteristics of solar cells
The output characteristics of solar cells are expressed in
the form of an I - V curve. An I - V curve test circuit and
typical I - V curve produced by the circuit are shown
below.
•
The I-V curve is produced by varying R
L
(load
resistance) from zero to infinity and measuring the
current and voltage along the way. The point at
which the I-V curve and resistance (R
L
) intersect is
the operating point of the solar cell. The current and
voltage at this point are Ip and Vp, respectively. The
largest operating point in the square area is the
maximum output of the solar cell.
1.6.
Dependence of cells on series
connection
When single solar cells are connected in series, the
voltage increases in proportion to the number of solar
cells which have been connected, as with ordinary
batteries. (Single cell voltage x number of cells)
1.7.
Light-sensing area and dependence
on light intensity
Increasing the light-sensing area or light intensity per
single solar cell produces a proportionate increase in the
short-circuit current. The open-circuit voltage remains
constant regardless of the light-sensing surface area, and
is hardly changed at all even by the intensity of light.
(However, it will drop drastically if the intensity of light
is reduced in the extreme.)
A
Test circuit
Light
Ammeter
Solar cell
V
R
L
Voltmeter
I-V curve
Operating point
Isc
Ip
Ip
1
2
Current
RL
Pmax
RL
Vp
Vp
2
2
1
1
Voc
Voltage
Isc
Voc
Ip
Vp
R
Pmax
: Short-circuit current
: Open-circuit voltage
: Operating current
: Operating voltage
: Load resistance
: Maximum output
L
0
0 Voc1 Voc2 Voc3
Voltage from
one cell
2 cells
connected
in series
3 cells
connected
in series
Current
Isc
Voltage
Voltage
Current
Light-sensing surface area
Intensity of light
Increase in light-sensing
surgace area
Increase in intensity of light
Decrease in light-sensing
surgace area
Decrease in intensity of light
Isc
Isc
Isc
1
2
3
Isc
4
0 Voc
