  We report on combined photoconductivity and annealing experiments in
whisker-like crystals of the Bi-Sr-Ca-Cu-O (BSCCO) high-Tc superconductor. Both
single-phase Bi2Sr2CaCu2O8+\delta (Bi-2212) samples and crystals of the mixed
phases Bi2Sr2Ca2Cu3O10+x (Bi-2223)/Bi-2212 have been subjected to annealing
treatments at 90{\deg}C in air in a few hours steps, up to a maximum total
annealing time of 47 h. At every step, samples have been characterized by means
of electrical resistance vs temperature (R vs T) and resistance vs time at
fixed temperature (R vs t) measurements, both in the dark and under
illumination with a UV-VIS halogen arc lamp. A careful comparison of the
results from the two techniques has shown that, while for single-phase samples
no effect is recorded, for mixed-phase samples an enhancement in the
conductivity that increases with increasing the annealing time is induced by
the light at the nominal temperature T = 100 K, i.e. at an intermediate
temperature between the critical temperatures of the two phases. A simple
pseudo-1D model based on the Kudinov's scheme [Kudinov et al., Phys. Rev. B 47,
9017-28, (1993)] has been developed to account for the observed effects, which
is based on the existence of Bi-2223 filaments embedded in the Bi-2212 matrix
and on the presence of electronically active defects at their interfaces. This
model reproduces fairly well the photoconductive experimental results and shows
that the length of the Bi-2223 filaments decreases and the number of defects
increases with increasing the annealing time.
