I want to measure Photosynthetically Active Radiation (PAR) of an LED light source.
Do I need a particular photodiode for measuring PAR of a LED light source?
Anyone know of a high quality photodiode? or a high quality supplier?
You will need a suitable bandpass filter for the illumination wavelengths of interest and a photodiode that has useful response in that range.
Good quality bandpass filters are not cheap. Edmund Scientific is a good source.
The photodetector (doesn't have to be a photodiode) must be sensitive in the 400-700nm range. One example is this here: SCD110 Photopic Light Detector
How accurate does this sensor have to be? What do you need it for?
For most LED lamps that are used for plant growing you usually detailed information about the color spectrum. So you could calculate the estimated PAR from a simple intensity measurement. I don't know if that's suitable for you.