I'm trying to measure solar radiation. Unfortunately I currently live in Bolivia, so I cannot get a solar cell. Instead I wanted to use a photodiode, but I wasn't able to find that either. Do you think that it is possible to measure solar radiation using a LDR? What about a phototransistor? An LDR's peak is around 550 nm, and the solar radiation comprehends a range from 500 to 2000nm. Plus bright sunlight implies around 30,000 lux while the cell's resistance for a LDR varies between 100 a 1000 lux.