  A functionally graded Al-doped ZnO structure is presented which combines
conductivity, visible transparency and light scattering with mechanical
flexibility. The nano and meso-architecture, constituted by a hierarchical,
large surface area, mesoporous tree-like structure evolving in a compact layer,
is synthesized at room temperature and is fully compatible with plastic
substrates. Light trapping capability is demonstrated by showing up to 100%
improvement of light absorption of a low bandgap polymer employed as the active
layer.
