What is the difference between a solar cell and a photodiode, in operation and as well as in construction?
All colleagues gave a satisfactory answer to the question of Ananth.
I would like to express the difference between the solar cell and the photodiode in few sentences and sum up what ha been said by the colleagues. Both are illuminated pn junction diodes but the the construction for the photodiode is to maximize the photo current , minimize the dark current ,minimize the noise generated by the diode , and making it sufficiently fast to work as a good photo sensor. While for solar cell,it is optimized to have the maximum conversion efficiency of the incident light to electrical energy. This is achieved by maximizing the photocurrent and the maximum output voltage. To work properly the photdiode operates in the third quadrant and the solar cell operates in the forth quadrant of the I-V characteristics.
emf is generated is a solar cell when light is incident upon it. however in a photodiode there is only reduction in resistance. One can measure the intensity of light by measuring the emf generated by a solar cell, and one can do the same by measuring current through a circuit with a photodiode and an external voltage source in a circuit.
Construction of photodiodes and solar cells are basically same as both of them have p-n junction which is used for charge creation and separation. That's why solar cells are also known as large area photodiodes. But one difference is that in photodiodes, response time to detect light signal is important whereas in solar cells ability to collect charges across the junction is important. Therefore, photodiodes are mainly designed to be operated in reverse bias whereas solar cells are designed to be operated in forward bias.
A photodiode is a semiconductor device that converts light into current. The current is generated when photons are absorbed in the photodiode. A small amount of current is also produced when no light is present. Photodiodes may contain optical filters, built-in lenses, and may have large or small surface areas. Photodiodes usually have a slower response time as its surface area increases. The common, traditional solar cell used to generate electric solar power is a large area photodiode.
Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacuum UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the device. Many diodes designed for use specifically as a photodiode use a PIN junction rather than a p-n junction, to increase the speed of response. A photodiode is designed to operate in reverse bias.
All colleagues gave a satisfactory answer to the question of Ananth.
I would like to express the difference between the solar cell and the photodiode in few sentences and sum up what ha been said by the colleagues. Both are illuminated pn junction diodes but the the construction for the photodiode is to maximize the photo current , minimize the dark current ,minimize the noise generated by the diode , and making it sufficiently fast to work as a good photo sensor. While for solar cell,it is optimized to have the maximum conversion efficiency of the incident light to electrical energy. This is achieved by maximizing the photocurrent and the maximum output voltage. To work properly the photdiode operates in the third quadrant and the solar cell operates in the forth quadrant of the I-V characteristics.
A photo diode is made to detect light quickly whereas a solar cell is made to collect energy from light. Both photo diode & solar cell are typically silicon diodes, but modified to meet their different requirements. A photo diode operates under Reverse biasing whereas a solar cell don't require any biasing. A photo diode has to be fast, which means low capacitance, which means small area of silicon. Therefore, it is not very sensitive, and cannot generate much power from light. On the other hand,a solar cell has as large an area as you can afford to buy, getting watts per square inch.
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