The PiN photodiode SFH206 from the vendor Osram was tested and characterised in the lab to obtain the power curve.
Photodiodes are fabricated with another uses and not for produce energy. But with the emerge of a new ultralow power devices or sensor nodes, this tiny photodiodes start to make sense in term of energy scavenging.
The output voltage circuit of the photodiode is much lower in comparison with a regular solar cells due to
physic properties of the photodiode. The open voltage circuit is for this SFH206 only 365 mV (from Datasheet).
The unit price is around 1.5€.
Another drawback is the huge package used for this part. The 5 mm LED package is large in comparison with the effective solar area, which is 2.65×2.65 mm. The special package form restrains to put
many of them together to obtain a bigger effective area.
Varying the load and the light conditions, the full power curve of the SFH-photodiode was obtained. As the lab LED was less powerful than the direct sunlight (obviously), the last “direct sun” curve has to be extrapolated with the open circuit voltage measured under the direct midday sun (480mV).