Ultrathin SnO₂ Scaffolds for TiO₂‐Based Heterojunction Photoanodes in Dye‐Sensitized Solar Cells: Oriented Charge Transport and Improved Light Scattering

Abstract

In this paper, band-structure matching strategy of a TiO2-based heterojunction within which electrons can be collected from TiO2 nanoparticles and transported rapidly in the bulk structure is reported. On the basis of the band-structure analysis of different TiO2-based heterostructures, focus was directed to the SnO2 nanosheet because of its appropriate band position and high electrical conductivity. Through a systematic investigation of the incorporation of ultrathin SnO2 nanosheet scaffolds for TiO2-based photoanodes in dye-sensitized solar cells (DSCs), we propose an anisotropy "constrained random walk" model to describe the controlled electron transit process. In this system, electrons are transferred orientedly overall, as well as randomly locally, leading to a significant reduction in the charge diffusion route compared to the conventional isotropic "random walk" model. In brief, the 2D ultrathin nanosheets provide rapid transit pathways and improved light-scattering centers, which can ensure a sufficient amount of dye loading and slow recombination. An overall light-to-electricity conversion efficiency as high as 8.25% is achieved by embedding the appropriate amount of SnO2 scaffold in a TiO2-based photoanode.

Graphene below the percolation threshold in TiO2for dye-sensitized solar cells

“…[25][26][27][28][29][30][31] Another recently exploited strategy relies on the addition of tin oxide nanosheets to TiO 2 anatase nanopowder, 32 featuring quite a high PCE (8.25%).…”

Hierarchically Structured ZnO Nanorods as an Efficient Photoanode for Dye‐Sensitized Solar Cells

“…Thus, the increased J SC for the nanorod photoanode relative to the nanoparticle electrode should be caused by the light scattering of the hierarchical nanorods. SEM and TEM images show that the hierarchical nanorods have submicrometer sizes, which are comparable to the wavelengths of visible light and thus expected to promote light scattering 21–23. The reflectance spectra of the films were measured to estimate the light‐scattering properties.…”

“…SEM and TEM images show that the hierarchical nanorods have submicrometer sizes, which are comparable to the wavelengths of visible light and thus expected to promote light scattering. [21][22][23] The reflectance spectra of the films were measured to estimate the light-scattering properties. Figure 6 compares the UV/Vis reflectance spectra of the nanorod and nanoparticle films.…”

Controlled Oriented Attachment of Bipyramidal‐Shaped Anatase TiO2 and Their Enhanced Performance in Dye‐Sensitized Solar Cells

“…[10] In spite of the short electron diffusion length, anatase TiO 2 still plays acrucial role in DSCs as ar esult of its appropriate electronic band gap and remarkable chemical stability. [11][12][13][14][15] Therefore, it is highly desirable to develop an ew synthetic method of preparing anataseT iO 2 that leads to low electrical resistance without sacrificing surfacea rea.It is known that adjacent particles can be spontaneously self-organized by an "oriented attachment" mechanism;a s ac onsequence the particles can share ac ommon crystallographic orientation, followed by the union of these particles at ap lanar interface. [16][17][18] Thism echanism shed light on the assembly of bipyramidal-shaped anatase TiO 2 enabling both large surface area and high electron conductivity.O fs ignificant importance is the goal to further tune the extent of oriented attachment, which would result in considerable improvement of the performance of TiO 2 in variousd evices,p articularly for DSCs.Herein, we developed an ew synthetic strategy to produce bipyramidal-shapeda natase TiO 2 and more importantly,t hese crystalsc an be further attached along the [001]d irection to form connected nanorods through tuning the reaction condition.…”

“…[10] In spite of the short electron diffusion length, anatase TiO 2 still plays acrucial role in DSCs as ar esult of its appropriate electronic band gap and remarkable chemical stability. [11][12][13][14][15] Therefore, it is highly desirable to develop an ew synthetic method of preparing anataseT iO 2 that leads to low electrical resistance without sacrificing surfacea rea.…”