where
k = Boltzmann’s constant = 8.62 × 10–5 eV/K = 1.38 × 10–23 joules/kelvin
T = the absolute temperature in kelvins = 273 + temperature in °C
q = the magnitude of electronic charge = 1.60 × 10–19 coulomb
Substituting k = 8.62 × 10–5 eV/K into Eq. (4.2) gives