- Solar Cell Definition: A solar cell (also known as a photovoltaic cell) is defined as a device that converts light energy into electrical energy using the photovoltaic effect.
- Working Principle: Solar cells generate electricity when light creates electron-hole pairs, leading to a flow of current.
- Short Circuit Current: This is the highest current a solar cell can provide under optimal conditions without being damaged.
- Open Circuit Voltage: The voltage across the solar cell’s terminals when there is no load connected, typically around 0.5 to 0.6 volts.
- Efficiency: The efficiency of a solar cell is the ratio of its maximum electrical power output to the input solar radiation power, indicating how well it converts light to electricity.
A Solar cell, or photovoltaic cell, is the basic device in a solar energy generation system that converts absorbed light directly into electrical energy. Its operation relies on the photovoltaic effect, which is why it is also called a photovoltaic cell. Most cells use a semiconductor absorber with contacts that collect photogenerated charge. The terminal potential difference and current depend on the cell technology, irradiance, spectrum, temperature, area and connected load. Unlike battery cells, solar cells do not store their own fuel. They produce direct current while illuminated, and their front and rear contact arrangement varies by design.
When light reaches the solar cell, photons with enough energy can be absorbed and create electron-hole pairs. The cell’s internal electric field and selective contacts separate and collect these carriers before they recombine. In a conventional silicon cell, a p-n junction helps form that field. Charge collection establishes a terminal potential difference; connecting a load allows conventional current to flow through the external circuit from the positive terminal to the negative terminal. Engineers compare a solar or photovoltaic cell through its measured current-voltage curve. The main parameters are short-circuit current, open-circuit voltage, maximum power, fill factor and conversion efficiency. Each rating is meaningful only with its stated test conditions.
Short Circuit Current of Solar Cell
The short-circuit current of a solar cell, Isc, is measured when its terminals are connected so that terminal voltage is zero. Device safety limits come from separate ratings. Its value changes with irradiance, spectrum, temperature and active area. Current density, Jsc, divides short-circuit current by the illuminated active area A, which makes cells of different sizes easier to compare when they are measured under the same conditions.
Here, Isc is short-circuit current, Jsc is short-circuit current density and A is the active area of the solar cell.
Open Circuit Voltage of Solar Cell
Open-circuit voltage, Voc, is measured across the cell terminals when current is zero. It depends on the semiconductor technology, irradiance and cell temperature. Many crystalline-silicon cells produce roughly 0.5 to 0.7 V under common rating conditions, but this range does not apply to every cell technology or operating condition.
Maximum Power Point of Solar Cell
The maximum-power point is the operating point on the current-voltage curve where a cell delivers its greatest electrical power for the stated test conditions. The power equals current multiplied by voltage. On the solar cell curve, it occurs near the bend and is labelled Pm. Both its position and value change with irradiance and temperature.
Current at Maximum Power Point
Im is the cell current at the maximum-power point on its current-voltage curve.
Voltage at Maximum Power Point
Vm is the cell voltage at the maximum-power point on its current-voltage curve.
Fill Factor of Solar Cell
Fill factor compares the maximum-power rectangle with the rectangle defined by the short-circuit current and open-circuit voltage of the solar cell. It equals maximum power divided by the product of short-circuit current and open-circuit voltage. A larger fill factor indicates a squarer current-voltage curve, but comparisons still require the same measurement conditions.
Efficiency of Solar Cell
Solar-cell efficiency is the maximum electrical output power divided by the incident optical power, expressed as a percentage. The incident power equals irradiance multiplied by the illuminated active area. Terrestrial standard test measurements commonly use a reference irradiance of 1000 W/m². Actual sunlight varies by place, time and weather. For active area A under that reference irradiance, the input power is 1000 A watts.
