Plasmonic Enhancement of Mesoporous Solar Cells with Shape Controlled Nanostructures
Department of Chemical and Biomolecular Engineering,
Vanderbilt University, Nashville, TN 37235
Next generation mesoporous solar cells (MSCs) including dye-sensitized solar cells (DSSCs) and perovskite-sensitized solar cells (PSSCs) have rapidly emerged with efficiencies reported up to 13% for DSSCs and 20% for PSSCs. Current efforts to improve the performance of MSCs are focused on altering the photoanode morphology, and manipulating the sensitizer composition. In contrast to these approaches that often lead to incremental improvement tailored to each MSC system, plasmonic enhancement provides a universal route applicable to the whole family of MSCs that can significantly boost the optical absorption and carrier generation. Through small additions of metal nanoparticles to MSCs (< 2%), the amount of sensitizer required to achieve high efficiency can be drastically reduced enabling thin film architectures compatible with scalable nanomanufacturing routes including roll-to-roll processing and inkjet printing. Here we demonstrate enhanced light harvesting in both DSSCs and PSSCs by embedding shape-controlled Au nanostructures, and Au/Ag core/shell bimetallic nanostructures in the photoanodes. Plasmonic enhancement resulted in 25 – 35 % enhancement in DSSCs and >15% enhancement in PSSCs. Photocurrent and IPCE spectra revealed that device performance in MSCs is controlled by particle density of plasmonic nanostructures and monotonically decreases at high concentrations. Transient absorption pump-probe spectroscopy revealed that presence of metal nanostructures leads to enhanced exciton generation, and faster electron injection into TiO2 conduction band before recombination can occur in the bulk, resulting in shorter exciton lifetime. This work shows that shape-controlled plasmonic nanostructures can be employed as a universal platform for enhanced light-trapping in a range of solar devices.