Self-assembled synthetic opals are suitable for integration into solution-processed thin film solar cells. In this work, finite-difference time-domain simulations are carried out to tailor optical properties of monolayer and multilayers of semiconductor spheres to trap light when these structures are incorporated into thin film solar cells. In particular, architectures in which spheres are filled with a photoactive material and embedded in a lower refractive index medium are examined. Based on spectra and field intensity maps, this study demonstrates that opal-like photonic crystals obtained from colloidal templates and filled with light-absorbing material can significantly harvest light by exploiting photonic band resonances.