Nd–Nb Co-doped SnO(2)/α-WO(3) Electrochromic Materials: Enhanced Stability and Switching Properties

[Image: see text] The fabrication of Nd–Nb co-doped SnO(2)/α-WO(3) 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-WO(3) without causing much lattice strain due to the similar ionic radius of Nb(5+) and W(6+). 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 SnO(2), improving the electronic conductivity and easing the insertion and extraction of Li(+) cations from the ECs. The enhanced Nd–Nb co-doped SnO(2)/α-WO(3) 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 SnO(2)/α-WO(3) presented in this work demonstrates an excellent candidate material for smart window applications to be used in green buildings.