The goal of this problem is to calculate the current from a photovoltaic cell as exactly as possible for a very simple case.

1. a) Explain what τp corresponds to.
2. b) Explain what it means for this solar cell problem to set ∂ ∆ pn = 0.

∂t

c) Assuming that x is measured from the depletion region edge at x = 0 show that

∆pn(x) = Aex/L +Be−x/L +C

is a solution for ∆pn(x) on the n-type side of the junction (to do this just substitute this

solution in and show it works).

1. d) Determine A, B, C, and L in terms of constants and ∆p(0) for the case of a long diode (you need to make some argument concerning A for this long diode).
2. e) Let the boundary condition at x = 0 be the same you used in EE3161, i.e.
3. ∆pn(0) = pno(exp(qV/kT)−1) (1)

1

EE4161

Homework Assignment Due Feb 1

Calculate the minority carrier diffusion current at x = 0 by computing J =−qD d∆p(x)

D pdx

at x = 0.

f) From the last result determine the constants for the diode current to be in the form:

jD=Jo(evD/VT −1)−JL

(note that the current density J=I/A and that Jo is JS in Mertens)