The BPW34 is a very common photodiode. It has a wide spectral response (visible and near infrared)and very high speed.
Spec Sheet: http://www.vishay.com/docs/81521/bpw34.pdf
Spectral Bandwidth: 430nm to 1100nm
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).
- 1 Op Amp
- 1 Resistor