Optimization of hierarchical light-scattering layers in TiO₂ photoelectrodes of dye-sensitized solar cells

In this report, we demonstrate a novel approach of introducing hierarchically arranged light-scattering layers (LSLs) into the TiO₂ photoelectrodes of dye-sensitized solar cells (DSSCs) to enhance the light-harvesting efficiency (LHE) in the visible region of light. The increase of LHE extended the photocurrent onset from higher wavelength in the incident photon-to-current conversion efficiency (IPCE) spectra of the DSSCs with LSLs. Further, the LHE of the TiO₂ photoelectrode was maximized when the LSLs were hierarchically arranged in the regular TiO₂ photoelectrodes. The optimized hierarchical LSLs enhanced the optical density inside the film by the effect of producing higher wavelength light gradually with an increase in scattering particle size. The IPCE of the cells was increased up to ca. 35% for wavelengths ranging from 550 to 800 nm as compared with cells without LSLs, which contributed to the enhancement of the PCE of the DSSCs from 7.08% to 9.37% with ca. 32% improvement over cells without scattering layers.