## AIM: To plot the I – V characteristics of solar cell and determine fill factor.

In this post, practical of I – V characteristics of solar cell and determination of fill factor method is given.

### Theory

The relation between solar cell voltage and current is given by

Id = Io ( eqv/kT – 1 )

Where

Id = diode current

q = Electron charge = 1.602 × 10 – 19 Coulomb

k = Boltzmann’s constant = 1.381 × 10 – 23 Joule / Kelvin

T = Junction Temperature in Kelvin

Id = Diode current

Io = Reverse saturation current

V = Voltage across diode terminal

At standard room temperature of 25 0C = 273.15 + 25 = 298.15 K

q/kT = (1.602 × 10 – 19 )/(1.381 × 10 – 23 )(298.15)

= 38.90

Id = Io ( e38.90v – 1 )

### Solar cell: Open circuit and short circuit

Actual solar cell in its equivalent circuit under two conditions are given here. When the solar cell terminals are short circuited, the current flows through lead or wire are ISC (short circuit current). When the leads of the solar cell are shorted together, no current flows through diode as voltage across solar cell Vd = 0. Similarly when load is open circuited and measure voltage across solar cell, no current flow through load and it is open circuited VOC (open circuited voltage).

### Instruments / Equipment Required

• Solar cell / Solar panel
• DC milli ammeter
• Voltmeter
• Multimeter
• Patch cords
• Light source

### Procedure

• Place the light source and solar cell in the opposite direction
• Switch on the light source.
• Make the light intensity to some fixed value.
• Make the connection as shown in the figure.

Short circuit condition

• Short the load resistance or make the load resistor is equal to zero and measure the current passing through load resistor.
• It is short circuit current ISC = _____________

Open circuit condition

• Make the ammeter circuit open circuited and measure voltage across solar cell
• It is open circuit voltage Voc = ____________
• Again, the circuit connection is done as per diagram.
• Vary the load resistor in step from low value to large value / large value to low value and note down the reading of voltmeter and ammeter.
• Plot graph between output voltage and current, taking voltage on x axis and current on y axis.
• In the I – V characteristics of solar cell, Voc and Isc are the end point of the solar cell characteristics in x axis and y axis respectively. Note down the reading of Vm and Im from the readings and show on the graph. The point corresponding to Vm and Im on I – V curve is known as maximum power point.

### Observation table

 Sr. No. Resistor Voltage Current 1 2 3 4 5 6

### Graph of IV Characteristics of solar cell

The I – V characteristics of solar cell is similar to that shown in the figure.

### Calculation

From the graph, Vm = ______ V & Im = _________ mA

Maximum useful power = Vm × Im

Ideal Power = Voc × Isc = _________ mW

Fill Factor = (Vm × Im) / (Voc × Isc)

### Conclusion

The fill factor is determined by I – V characteristics of solar cell. The fill factor is an important parameter to determine the efficiency of solar cell. Higher the fill factor, more rectangular the I – V curve.

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