Bragg gratings nanostructuring of TiO2 layer in dye sensitized solar cells: an efficient method to enhance light harvesting

In this paper, we report an experimental procedure for active layer nanostructuring in Dye Sensitized Solar Cells (DSCs) to enhance light harvesting. A Bragg grating has been realized on a high performance commercial photoresist by means of the Laser Interference Lithography (LIL) technique. Subsequently this structure has been replicated by a Soft Lithographic process on a polydimethylsiloxane (PDMS) mold, which finally allowed the direct imprinting of the DSC's titania layer under UV illumination. Morphological analysis demonstrated a successful pattern transfer over a large area. Spectroscopic and photovoltaic measurements have been performed on nanostructured and traditional bare DSCs. In the spectral range 500–750 nm the patterned cell showed a lower transmission and reflection indicating that the grating acts efficiently as a light harvesting element. I–V and Incident Photon to Current Efficiency (IPCE) characterization showed an enhancement of 31% of the cell efficiency, confirming the effectiveness of this method.