The BPW34 is modeled based on its datasheet.
The solar spectrum selectivity is set at 550nm
(near the solar spectrum peak) which is about 38.3%
from the sensor 950nm nominal current at 47uA/mW/cm^2.
Therefore the measured current in BPW34 set at 18uA/10W/m^2.
With 56 ohm resistor, the sensitivity is about 0.1mV / 1W/m^2.
Rodney Tan (2020). BPW34 Photodiode Solar Radiation Sensor (https://www.mathworks.com/matlabcentral/fileexchange/74668-bpw34-photodiode-solar-radiation-sensor), MATLAB Central File Exchange. Retrieved .