The BPW34 is a very common photodiode. It has a wide spectral response and can be used as a light sensor.   

The BPW34 is a very common photodiode. It has a wide spectral response (visible and near infrared)and very high speed.   

'''Spec Sheet:''' http://sccatalog.honeywell.com/pdbdownload/images/ss5.series.chart.1.pdf

'''Spec Sheet:''' http://www.vishay.com/docs/81521/bpw34.pdf

''Voltage In:'' 3.8 V ~ 30 V

''Spectral Bandwidth:'' 430nm to 1100nm

''Supply Current:'' 6mA

''Highlights:'' It is an ideal replacement for photocells however it is a current device and requires an amplifier circuit as the one shown below to function properly. Also it's reponse is much faster than that of a photocell (100ns compared to 10ms).