Charge Transfer in Mixed-Phase TiO2 Photoelectrodes for Perovskite Solar Cells

Abstract

In mesoscopic perovskite solar cells (PSCs) the recombination processes within the TiO2 photoelectrode and at the TiO2/perovskite interface limit power conversion efficiency. To overcome this challenge, we investigated the effect of TiO2 phase composition on the electronic structure of TiO2 photoelectrodes, as well as on PSCs performance. For this, a set of PSCs based on TiO2 thin films with different content of anatase and rutile particles was fabricated under ambient conditions. X-ray diffraction, optical spectroscopy and scanning electron microscopy were used to study the structural, morphological and optical characteristics of TiO2 powders and TiO2-based thin films. X-ray photoelectron spectroscopy (XPS) analysis of anatase revealed a cliff conduction band alignment of 0.2 eV with respect to the rutile. Energy band alignment at the anatase/rutile/perovskite interfaces deduced from the XPS data provides the possibility for interparticle electron transport from the rutile to anatase phase and the efficient blocking of electron recombination at the TiO2/perovskite interface, leading to efficient electron-hole separation in PSCs based on mixed-phase TiO2 photoelectrodes. PSCs based on TiO2 layers with 60/40 anatase/rutile ratio were characterized by optimized charge extraction and low level of recombination at the perovskite/TiO2 interface and showed the best energy conversion efficiency of 13.4% among the studied PSCs. Obtained results provide a simple and effective approach towards the development of the next generation high efficiency PSCs.

Investigation of UV Dye-Sensitized Solar Cells Based on Water Electrolyte: A New Insight for Wavelength-Selective Greenhouse

“…From the diffuse reflectance spectra, presented in Figure 6, the optical dire gaps of the TiO2 photoelectrode materials were estimated by using the Tauc plot [ intercepting the extrapolated linear fit for the plotted experimental data of (αhν) incident photon energy (hν) near the absorption edge. The obtained values of 3.12 3.09 eV for TiO2_NP and TiO2_LS1, respectively, are comparable to the data rep the literature for anatase and rutile polymorphs of TiO2 structures [24]. The value eV obtained for the TiO2_LS2 sample is much higher than previously reported v mixed anatase-rutile TiO2 nanoparticles [25].…”

Perovskite Solar Cells with an SbX3 (X = Cl, I) Interface Dipole Layer

“…Meanwhile, the cliff-type CBM offset is reduced from 0.32 to 0.19 eV (Δ 3 = 0.13 eV). Given the consistency between Δ 1 , Δ 2 , and Δ 3 , it is safe to claim that adding an SbCl 3 layer produces an interface dipole pointing toward the oxide substrate, enhanced n-type characteristics in the perovskite, and a reduced cliff-type CBM offset. − All of these together suggest an energy-level alignment favoring the enhancement of V bi and V OC .…”

High performance tandem perovskite-silicon solar cells with very large bandgap photoelectrodes

“…ZrO 2 and HfO 2 nanoparticles were obtained by hydrothermal treatment of co-precipitated zirconium and hafnium hydroxides from solutions of the corresponding metal salts [21]. TiO 2 nanoparticles (P25 Aeroxide Degussa) were purchased from Sigma-Aldrich (USA) and were used for fabrication of state-of-the-art TiO 2 photoelectrode [22]. Thick pastes from MO 2 (where M=Ti, Zr or Hf) nanopowders were prepared in organic solvent following the method described in [23].…”