Solar Cell
AIM: To study the current-voltage output using a solar cell
THEORY:
A solar cell is basically a p-n junction diode which converts solar energy into electrical energy.
This conversion of optical energy into electrical energy is known as ‘Photo voltaic effect’.
When a solar cell is illuminated, the photons incident on the cell generate electron hole pairs.
By diffusion in the material the electrons and holes reach the junction. At the junction, the barrier
field separates the positive and the negative charge carriers. Under the action of the electric field,
the electrons from the p-region are swept into the n-region. Similarly, the holes from the n-region
are swept into the p-region. This accumulation of charges on two sides of the junction produces
an emf called the photo emf. This photo emf is proportional to the illumination (expressed in
mW/cm2 or lumen/cm2) and on the size of the illuminated area.
When an external circuit is connected across the solar cell terminals, the minority carriers
return to their original sides through the external circuit, causing a current to flow through the
circuit. Thus the solar cell behaves as a battery with n-side as the negative terminal and p-side as
the positive terminal. The photo emf is thus measured with a voltmeter.
EXPERIMENTAL OBSERVATION:
Table 1: Current-Voltage relationship
No. of Filament Load Current(mA) Voltage Power P=V.I
obs. voltage range resistance(ohm) (Volt) (mW)
0
Intensity is low
Intensity is
medium
Table 2: Area characteristics
Light intensity = max
Resistance: …….
Chopper area(cm2) Voltage(V) Current(mA) Power(mW)
Table 3: Frequency characteristics
Light intensity = max
Resistance: ……
Colour of the Frequency of the filter(1015 Voltage Current(mA) Power(mW)
filter Hz) (V)
0.450
0.511
0.598
0.678
GRAPH:
(No marks for showing calculations)
PERCENTAGE ERROR:
= = .01 Volt
I = .01 mA
Percentage error = 100%
EXPECTED NATURE OF THE GRAPHS:
PROCEDURE:
1. Illumination characteristics: Set the load resistance to zero. Vary the voltage across the light
bulb. Record the photo current. Draw a graph.
2. Current-voltage characteristics:
● keep the intensity of the lamp at a low value. Note the open circuit voltage . short the
output of the solar cell and note the short circuit current.
● Change the load resistance in steps of 100 ohm. Record the corresponding current and
voltage. Draw a graph with v in the x axis and current in the y-axis.
● This step can be repeated with other values of the filament voltage.
3. Power-load characteristics: calculate power from the current-voltage data obtained in the
previous step and plot against the load resistance. Find out the optimum value of the load for
which the power dissipation is the maximum.
4. Area characteristics: Set the load at the optimum value obtained from the previous step. Set
the chopper in the slot provided in front of the solar cell in different settings and measure the
current and voltage. Calculate the power. Draw a graph of the power vs. the area of the chopper
settings.
5. Frequency characteristics: Keeping the load at its optimum value put several filters and take
the current-voltage data to get the power. Plot a graph of power vs. frequency of the filter.
DISCUSSION:
