Is the SSM2019 an appropriate IC for a optical sound solar cell preamplifier?
For a variable area or variable density (OLD Movies!) track you will have audio riding on a fairly large DC bias, which will need removing before amplification. 

I would suggest a series cap of maybe 47uF into a simple 5532 based amp is usually going to be at least as good as whatever was used originally, but actually a standard mic amp should do just fine, with a few tens of mV out of the cell you should only need ~30 - 40dB of gain to get to the usual sort of volt or so of line level.

Have you considered the need for de-emphasis in the playback processing (Either the "Academy" curve for mono sound tracks or the "X Curve" for Stereo variable area? It will likely sound severely odd without these, and that is before we consider Dolby.

One other gotcha is the existence of modern 'Cyan dye' prints which have replaced the silver halide with a dye which is transmissive to IR from the exciter lamp, to get optical sound to work with these films you need to replace the exciter with a laser source. 

Sounds like a fun project.