Light Trapping Color Filters for Semitransparent Solar Cells

Semitransparent colorful solar cells equipped with photonically tailored Fabry-Perot (FP) cavities as the back electrode have garnered attention for their prospective application in building integrated photovoltaics (BIPVs). These cells transmit colored light at the FP resonance while reflecting nonresonant light back into the cell, a significant portion of which is also lost into air. Herein, we present a method to enhance light trapping in colorful semitransparent solar cells using closely packed Ag-coated silica particles on a thin Ag layer. This structure simultaneously acts as an effective FP cavity and color filter, scattering off-resonant light to high angles while transmitting the targeted colors. We show that the high-angle scattering originates from antiparallel out-of-plane electric dipoles unique to our design, which promote light trapping. When applied onto a dye-sensitized solar cell (DSSC), our effective Fabry-Perot (EFP) color filters provided a maximum of ∼7% more short-circuit current density (J_sc) than those from DSSCs equipped with planar filters. Furthermore, compared to bare DSSCs and DSSCs including conventional scattering layers, DSSCs equipped with EFP filters showed a maximum of 14.6 and 5.9% higher cell efficiencies (η), respectively. The ability to filter color and improve light trapping suggests alternative pathways for engineering colorful semitransparent solar cells.