What is Photodiode responsivity ?
Definition: The responsivity of silicon photodiode is a measure of sensitivity to light. It is defined as ratio of photocurrent (Ip) to incident light power P at given wavelength.
Responsivity, Rλ = Ip/P
In other words, it is measure of the effectiveness of conversion of light power into electric current. It varies with the wavelength of incident light, applied reverse bias and temperature.