Review on S12SD 200-370nm UV Detection Sensor Module Light Sensor for Arduino - Optimize Your Search! by Jayme Newitt

Amplifier gain saturates the output (5V supply) with less than 20nA from the photodiode. The diode specs show that 1mW/cm^2 should produce about 110 nanoamps. This makes the maximum value of the sensor about 1/6 mW/cm^2 (if the diode output is reasonably linear). With the calculated gain of the current amplifier and the transconductance amplifier, the dark current is actually about 1 nanoamp as shown in the datasheet. The sales figures also imply that the amplifier can be used as a UV index meter. This is only possible by swapping the feedback resistor on the current amplifier. The way it's constructed, the performance saturates in direct sunlight.