The analysis of internal quantum efficiency data is extended by a new
graphical evaluation scheme. On the one hand, our method allows one to
estimate the minority carrier diffusion length L and the back surface
recombination velocity S. On the other hand the limitations of the in
ternal quantum efficiency method are studied. A mathematical treatment
of the equations describing internal quantum efficiency demonstrates
that already a single measurement of either the effective diffusion le
ngth L(eff) measured in the near infrared, or the collection efficienc
y eta(c) measured in the near bandgap wavelength range, yields limits
for L and S. More precise values can be obtained in specific cases, if
the analysis of L(eff) and eta(c) are combined. In those cases, infor
mation about the accuracy of L and S is obtained. We present a graphic
al solution for the evaluation and illustrate our method using quantum
efficiency data from both thick and thin silicon solar cells.