It's confusing. The first e is just the base of the natural logarithms (2.718...), but the e in the exponent is the charge on the electron. I prefer to write it as:
[tex]e^\frac{qV}{kT}[/tex] to eliminate this confusion. Note that if you measure kT in electron volts (eV), then the electron charges cancel, and you can just use the voltage V directly. Note that at room temperature, kT is .026 eV, so you can write:
[tex]I = I_0 e^\frac{V}{.026}[/tex]