A first order theory of the edge-illuminated p
+-n-n
+silicon solar cell under very high injection levels has been derived. The very high injection level illuminated

characteristic is derived for any general base width to diffusion length (

) ratio and it includes the minority carrier reflection by the n-n
+high-low junction. The beneficial effects of the high-low junction are shown to be significant until extremely high injection levels are reached. The theoretical dependencies of J
scand V
ocon temperature, incident intensity, and base resistivity are derived and discussed in detail. Some experimental results are given and these are discussed in relation to the theory.