I think that's a bit beside the point. A photomultiplier has a pre-charged state where a photon triggers an avalanche -- not really relevant for photovoltaic a

I think that's a bit beside the point. A photomultiplier has a pre-charged state where a photon triggers an avalanche -- not really relevant for photovoltaic applications. The question was more if you can lift three electrons trough the band gap, triggered by a single photon, which would increase the solar cell's output current without dropping the voltage.