Editing Photodiode (section)

===Photovoltaic mode===

[[File:Photodiode operation-en.svg|thumb|350px|I-V characteristic of a photodiode. The linear [[Load line (electronics)|load lines]] represent the response of the external circuit: I=(Applied bias voltage-Diode voltage)/Total resistance. The points of intersection with the curves represent the actual current and voltage for a given bias, resistance and illumination.]]

In photovoltaic mode (zero [[bias (electrical engineering)|bias]]), photocurrent flows into the anode through a short circuit to the cathode.  If the circuit is opened or has a load impedance, restricting the photocurrent out of the device, a voltage builds up in the direction that forward biases the diode, that is, anode positive with respect to cathode.  If the circuit is shorted or the impedance is low, a forward current will consume all or some of the photocurrent. This mode exploits the [[photovoltaic effect]], which is the basis for [[solar cell]]s – a traditional solar cell is just a large area photodiode.  For optimum power output, the photovoltaic cell will be operated at a voltage that causes only a small forward current compared to the photocurrent.<ref name=haberlin/>