Semiconductors are certain type of metals which allow only partial current to pass through them in one direction only.
The conductivity of a semiconductor increases when light falls on them. Their conductivity also increases if certain impurities are added to them. Materials like silicon, selenium, cadmium sulphide or copper sulphide act as semiconductors.
In a solar cell, the pieces (wafers) of semi conducting materials containing impurities are so arranged that a potential difference develops between two regions of the semiconductors when light falls on it.
Image Source: colorado-solar.org
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Thus when solar radiations fall in a solar cell, it converts solar energy into electrical energy. A lead storage battery is connected in the circuit which gets charged and can be used as and when desired.
The power generated by a single solar cell is very low. A single solar cell with an area of 4 cm2 has an output voltage of about 0.4-0.5 volts at 60 mill amperes of current.
Therefore, a large number of solar cells are mounted together to generate appreciable electrical power. The solar cells are arranged in series to form solar panels.
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Solar panel cells are mostly used in space satellites which remain in outer space for many years.
The space satellite contains solar panels which convert sunlight energy into electrical energy and thus electrical energy is used by satellite to operate various functions.