Combined Strategy to Realize Efficient Photoelectrodes for Low Temperature Fabrication of Dye Solar Cells

Abstract

We implemented a low-temperature approach to fabricate efficient photoanodes for dye-sensitized solar cells, which combines three different nanoarchitectures, namely, a highly conductive and highly transparent AZO film, a thin TiO2-blocking layer, and a mesoporous TiO2 nanorod-based working electrode. All the components were processed at T≤200°C. Both the AZO and the TiO2 blocking layers were deposited by reactive sputtering, whereas the TiO2 nanorods were synthesized by surfactant-assisted wet-chemical routes and processed into photoelectrodes in which the native geometric features assured uniform mesoporous structure with effective nanocrystal interconnectivity suitable to maximize light harvesting and electron diffusion. Because of the optimized structure of the TiO2-blocking/AZO bilayer, and thanks to the good adhesion of the TiO2 nanorods over it, a significant enhancement of the charge recombination resistance was demonstrated, this laying on the basis of the outstanding power conversion efficiency achievable through the use of this photoanode's architecture: a value of 4.6% (N719) was achieved with a 4-μm-thick electrode processed at T=200°C. This value noticeably overcomes the current literature limit got on AZO-based cells (N719), which instead use Nb-doped and thicker blocking layers, and thicker nanostructured photoanodes, which have been even sintered at higher temperatures (450-500°C).

Multi-Scale-Porosity TiO2 scaffolds grown by innovative sputtering methods for high throughput hybrid photovoltaics

“…More recently, hybrid solar cells replacing the dye with hybrid Perovskites (PSC) materials1819202122 as sensitizer allowed getting efficiency values as high as 22.1% using advanced mixed perovskites2324. In the standard scheme of the photo-anode of a DSC4 or PSC18, a mesoporous thin film of nanosized TiO 2 crystals is deposited on a Transparent Conductive Oxide (TCO), annealed for grains sintering and anatase crystallization (typically at 500 °C), and subsequently imbued with a photoactive dye2526272829 or infiltrated with perovskite30. In both cases, mesoporous TiO 2 in the anatase polymorphism has emerged as the most appropriate choice for cell scaffold15212331.…”

Structural Transitions in Nanosized Zn0.97Al0.03O Powders under High Pressure Analyzed by in Situ Angle-Dispersive X-ray Diffraction

“…AZO is a transparent conducting oxide (TCO) with reasonable electrical resistivity (~10 −4 Ω cm) and large transmittance (~92%), making it an attractive candidate for transparent conducting electrode in photoelectric devices. It has been demonstrated that an accompanying free electron is paired with the process when a Zn 2+ cation is replaced by an Al 3+ cation, which is responsible for the increased conductivity [39,40,41]. Furthermore, Figure 3c shows the SEM image for the A 3 ZO-NPs obtained by the present chemical precipitation and 500 °C calcination processes.…”

Controlled Al3+ Incorporation in the ZnO Lattice at 188 °C by Soft Reactive Co-Sputtering for Transparent Conductive Oxides

“…Spatial disuniformities in the layer thickness or in its surface roughness, with the eventual presence of deleterious protrusions, would affect the series resistance or generate parasitic currents (respectively) [10,22,23]. In situ EDX analyses provided an average atomic percentage of Al 3+ inside the ZnO lattice of ~2%, (inset of Figure 2).…”