Nd-Nb Co-doped SnO2/α-WO3 Electrochromic Materials: Enhanced Stability and Switching Properties

Ronn Goei; Amanda Jiamin Ong; Jun Hao Tan; Jie Yi Loke; Shun Kuang Lua; Daniel Mandler; Shlomo Magdassi; Alfred Iing Yoong Tok

doi:10.1021/acsomega.1c03260

Nd-Nb Co-doped SnO₂/α-WO₃ Electrochromic Materials: Enhanced Stability and Switching Properties

ACS Omega. 2021 Sep 28;6(40):26251-26261. doi: 10.1021/acsomega.1c03260. eCollection 2021 Oct 12.

Authors

Ronn Goei^{1

2}, Amanda Jiamin Ong^{1

2}, Jun Hao Tan¹, Jie Yi Loke¹, Shun Kuang Lua¹, Daniel Mandler^{2

3}, Shlomo Magdassi^{2

3}, Alfred Iing Yoong Tok^{1

2}

Affiliations

¹ School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
² Singapore-HUJ Alliance for Research and Enterprise, NEW-CREATE Phase II, Campus for Research Excellence and Technological Enterprise (CREATE), Singapore 138602, Singapore.
³ Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.

Abstract

The fabrication of Nd-Nb co-doped SnO₂/α-WO₃ electrochromic (EC) materials for smart window applications is presented in the present paper. Nb is a good dopant candidate for ECs owing to its ability to introduce active sites on the surface of α-WO₃ without causing much lattice strain due to the similar ionic radius of Nb⁵⁺ and W⁶⁺. These active sites introduce more channels for charge insertion or removal during redox reactions, improving the overall EC performance. However, Nb suffers from prolonged utilization due to the Li⁺ ions trapped within the ECs. By coupling Nd with Nb, the co-dopants would transfer their excess electrons to SnO₂, improving the electronic conductivity and easing the insertion and extraction of Li⁺ cations from the ECs. The enhanced Nd-Nb co-doped SnO₂/α-WO₃ exhibited excellent visible light transmission (90% transmittance), high near-infrared (NIR) contrast (60% NIR modulation), rapid switching time (∼1 s), and excellent stability (>65% of NIR modulation was retained after repeated electrochemical cycles). The mechanism of enhanced EC performance was also investigated. The novel combination of Nd-Nb co-doped SnO₂/α-WO₃ presented in this work demonstrates an excellent candidate material for smart window applications to be used in green buildings.