Its not the photodiode or solar cell you choose, but how you bias and load it.
In photovoltaic mode, most silicon devices need a 400-2000 ohm load across them. In photocurrent mode, most photodiodes want 9-15V of reverse bias across them to make them Linear. Some just need a bias voltage and the input of the scanner amp is the transimpedance device.
google "photodiode transimpedance amplifier"
Also overdriving the leds oversaturates the cell. Keep the cell area small if possible.
Also, drive the leds with a constant current source.
Some papers here might help:
www.electrooptical.net Dr Phil Hobbs. In fact if you email Phil he will probably help you.
However do NOT use a phototransistor.
Ask Norm what he uses.
http://www.ctrnd.com/NormLaserShow/LatestNews.htm
Elm chan uses simple RF.
http://elm-chan.org/works/vlp/report_e.html
Good Luck,
Steve
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