Wrinkled silica/titania nanoparticles with tunable interwrinkle distances for efficient utilization of photons in dye-sensitized solar cells

Abstract

Efficient light harvesting is essential for the realization of high energy conversion efficiency in dye-sensitized solar cells (DSCs). State-of-the-art mesoporous TiO2 photoanodes fall short for collection of long-wavelength visible light photons, and thus there have been efforts on introduction of scattering nanoparticles. Herein, we report the synthesis of wrinkled silica/titania nanoparticles with tunable interwrinkle distances as scattering materials for enhanced light harvesting in DSCs. These particles with more than 20 times larger specific surface area (>400 m(2)/g) compared to the spherical scattering particles (<20 m(2)/g) of the similar sizes gave rise to the dye-loading amounts, causing significant improvements in photocurrent density and efficiency. Moreover, dependence of spectral scattering properties of wrinkled particles on interwrinkle distances, which was originated from difference in overall refractive indices, was observed.

Figure 1

Schematic image displaying the synthesis of silica/titania nanoparticles and their photovoltaic application.

Figure 2

SEM images of wrinkled silica nanoparticles with different interwrinkle distances controlled by the amount of added co-solvent (1-pentanol); (a) 0.16 mL, (b) 0.33 mL, (c) 0.65 mL, and (d) 1.30 mL.

Figure 3

SEM images of scattering particles before (a,c,e,g) and after (b,d,f,h) heat treatment at 500 °C in air; (a,b) SSTNs, (c,d) STNs, (e,f) NWSTNs, and (g,h) WWSTNs.

Figure 4

TEM images of (a) NWSNs, (b) WWSNs, (c,e) NWSTNs, and (d,f) WWSTNs (c,d) before and (e,f) after heat treatment at 500 °C in air.

Figure 5

STEM images and corresponding elemental O, Si, and Ti EDS maps of (a) SSTNs, (b) NWSTNs, and (c) WWSTNs.

Figure 6

XRD patterns of WWSTNs, NWSTNs, SSTNs, and STNs after 500 °C heat treatment in air.

Figure 7

Absorbance spectra of N719 dye molecules detached from P25 and various scattering particles in 1 M NaOH solution.

Figure 8

Diffuse reflectance spectra of (a) silica nanoparticles and (b) silica/titania and titania nanoparticles measured by using an integrating sphere.

Figure 9

(a) J-V characteristics and (b) IPCE spectra of reference DSC and DSCs employing spherical or wrinkled scattering nanoparticles.

Figure 10

(a) OCVD curves of DSC and DSCs employing spherical or wrinkled scattering nanoparticles. The electron lifetimes calculated from the OCVD results are displayed in the inset. (b) Electrochemical impedance spectra of reference DSCs with or without scattering particles.