A photodiode is a transducer that functions by converting light into electrical energy. Light absorbed through the active area of a photodiode forms an electron-hole pair, which generates current through the photovoltaic effect. Photodiodes generate current that is proportionate the amount of light exposure they receive.
Photodiodes are essentially light detecting electronic components that are able to convert light energy into usable electrical power. Similar to semiconductor diodes in many respects, photodiodes must be either exposed to light or make use of an optical fiber connection in order to function. These components are commonly found in smoke detectors and infrared remote control devices. Silicon photodiodes are usually constructed from a single silicon crystal wafer that is of higher purity than the wafers used to manufacture integrated circuits.
Photodiodes will typically operate in either photovoltaic mode or photoconductive mode. In photovoltaic mode, the flow of current from the diode is restricted and voltage within the diode accumulates while in photoconductice mode the inverse is true. The amount of current photodiodes are able to produce is limited by their overall size and diodes need to be made larger in order to provide the surface area required to generate higher levels of current that may be needed by some circuits and devices.