Plasmonic colloidal Nb-doped TiO2 nanocrystals with improved electrochromism in visible-infrared region

Abstract

Dual-band electrochromic materials can achieve separate modulate of visible and near-infrared (NIR) transmittance, which are important components of smart windows. A promising colloidal Nb-doped TiO2 anatase nanocrystals (NCs) was prepared via the fluoride-assisted synthesis technique. The dual-band electrochromic properties of the NCs are closely related to the localized surface plasmon resonance (LSPR) absorption intensity. With the assistance of fluoride anions, TiO2 NCs can be easily doped with Nb, which is an important discovery. The product is a highly uniform Nb-doped TiO2 colloidal solution. Spectral analysis clarified that the Nb5+ replaced Ti4+, resulting in free carrier generation in the TiO2 conduction band, thereby exciting LSPR. Moreover, Nb-doped TiO2 NCs exhibited outstanding dual-band electrochromic properties including a wide modulation range for visible and NIR region (92.8 % at 620 nm and 75.2 % at 1800 nm) and a high electrochemical cycling stability (83.1 % at 620 nm and 70.3 % at 1800 nm after 1800 cycles). As a novel kind of electrochromic materials, the Nb-doped TiO2 NCs have great potential application for the smart windows.