Enhancing light harvesting by hierarchical functionally graded transparent conducting Al-doped ZnO nano- and mesoarchitectures

•Al-doped ZnO structures were engineered at the nano-, meso- and microscale.•Graded architectures combine transparency, conductivity and light scattering.•Room temperature synthesis allows deposition on polymers and bending.•Light harvesting efficiency substantially increases due to light scattering.

A functionally graded Al-doped ZnO structure is presented which combines conductivity, visible transparency and light scattering with mechanical flexibility. The nano- and meso-architectures, constituted by a hierarchical, large surface area, mesoporous tree-like structure evolving in a compact layer, are synthesized at room temperature and are 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.

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