  Angular-resolved photoemission data on half-filled doped cuprate materials
are compared with an exact-diagonalization analysis of the three-band Hubbard
model, which is extended to the infinite lattice by means of a perturbation in
the intercluster hopping (cluster perturbation theory). A study of the band
dispersion and spectral weight of the insulating cuprate Sr$_2$CuO$_2$Cl$_2$
allows us to fix a consistent parameter set, which turns out to be appropriate
at finite dopings as well. In the overdoped regime, our results for the
spectral weight and for the Fermi surface give a good description of the
experimental data on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. In particular, the
Fermi surface is hole-like and centered around $k=(\pi,\pi)$. Finally, we
introduce a hopping between two layers and address the issue of bilayer
splitting.
