What is going on when a solar cell goes into reverse bias

[ecvolt]

I would like to understand exactly what happens when a PN doped crystalline silicon cell is shaded. Lets assume we have ten solar cells wired together in a series sting.That there is plenty of sunlight on the first nine cells but cell ten is completely shaded.Lets say that the forward bias of each solar cell is .5 volts lets say the conventional current is moving from anode to cathode and the Electron flow is cathode to anode.This would make the anode more positive {more holes} than the cathode {more electrons}.When current is flowing in the first nine cells at a forward bias how does that tenth cell reverse in bias?Do the other nine cells which are getting plenty of photons from the sun go into reverse bias also?What causes the shaded tenth cell to create extreme amount of heat.Lets asume we have no by pass diodes in this ten celled string .Lets assume this collection of cells is a solar module.Thank you ecvolt