Explanation of 5 Parameter Model for Solar Cells
Well, this is silly. The answer I was looking for was in a Wikipedia post on the Theory of Solar Cells. Basically these types of equations are solved using the Lambert W function.

The original equation

\$I = I_{ph} - I_o[\exp(\frac{V + R_sI}{nV_t})-1] - (\frac{V+R_sI}{R_{sh}})\$

becomes

\$I=\frac{(I_{ph}+I_o)-V/R_{sh}}{1+R_s/R_{sh}}-\frac{nV_t}{R_s}W(\frac{I_oR_s}{nV_t(1+R_s/R_{sh})}\exp(\frac{V}{nV_t}(1-\frac{R_s}{R_s+R_{sh}})+\frac{(I_{ph}+I_o)R_s}{nV_t(1+R_s/R_{sh})}))\$

Now its very simple to calculate the current and power.