Spontaneous Synthesis of Highly Crystalline TiO2 Compact/Mesoporous Stacked Films by a Low-Temperature Steam-Annealing Method for Efficient Perovskite Solar Cells

Yoshitaka Sanehira; Youhei Numata; Masashi Ikegami; Tsutomu Miyasaka

doi:10.1021/acsami.8b03532

Spontaneous Synthesis of Highly Crystalline TiO₂ Compact/Mesoporous Stacked Films by a Low-Temperature Steam-Annealing Method for Efficient Perovskite Solar Cells

ACS Appl Mater Interfaces. 2018 May 23;10(20):17195-17202. doi: 10.1021/acsami.8b03532. Epub 2018 May 14.

Authors

Yoshitaka Sanehira¹, Youhei Numata², Masashi Ikegami¹, Tsutomu Miyasaka¹

Affiliations

¹ Graduate School of Engineering , Toin University of Yokohama , 1614 Kurogane-cho , Aoba, Yokohama , Kanagawa 225-8503 , Japan.
² Research Center for Advanced Science and Technology (RCAST) , The University of Tokyo , 4-6-1 Komaba , Meguro, Tokyo 153-8904 , Japan.

PMID: 29727154
DOI: 10.1021/acsami.8b03532

Abstract

Highly crystalline TiO₂ nanostructured films were synthesized by a simple steam treatment of a TiCl₄ precursor film under a saturated water vapor atmosphere at 125 °C, here referred to as the steam-annealing method. In a single TiO₂ film preparation step, a bilayer structure comprising a compact bottom layer and a mesoporous surface layer was formed. The mesoporous layer was occupied by bipyramidal nanoparticles, with a composite phase of anatase and brookite crystals. Despite the low-temperature treatment process, the crystallinity of the TiO₂ film was high, comparable with that of the TiO₂ film sintered at 500 °C. The compact double-layered TiO₂ film was applied to perovskite solar cells (PSCs) as an electron-collecting layer. The PSC exhibited a maximum power conversion efficiency (PCE) of 18.9% with an open-circuit voltage ( V_OC) of 1.15 V. The PCE and V_OC were higher than those of PSCs using a TiO₂ film formed by 500 °C sintering.

Keywords: TiO2; electron transport layer; low-temperature process; perovskite solar cell; solvent-free hydrothermal synthesis; steam-annealing method.