High performance inorganic all-solid-state electrochromic devices based on Si3N4 ion conducting layer

In electrochromic devices (ECDs), ion conducting layer has the vital function of conducting ions and blocking electrons. However, the limited electron blocking ability and preparation technology of conventional ion con-ducting materials hinder the commercial application of all-solid-state ECDs. In this work, a novel ion conducting material Si3N4 film was deposited by pulsed direct current (p-DC) reactive magnetron sputtering with a Si target, and shows promising potential due to its ultrahigh transparency, anti-reflection effect and remarkable electron blocking ability. An ECD with the structure of glass/ITO/WO3/Li/Si3N4/NiO/ITO has been fabricated by magnetron sputtering, in which Si3N4 film was used as ion conducting layer for the first time. The ECD presents much less leakage current density (<35 mu A cm-2), large optical transmittance modulation (72.3% at 625 nm), fast response (1.3 s for bleaching and 13.1 s for coloring), high coloration efficiency (94.46 cm2 C-1) and excellent cycle stability (91.4% retention of the maximum optical modulation after 10,000 cycles). This work not only demonstrates the great prospect of Si3N4 film as an ion conducting layer in ECDs, but also provides a new idea in the selection of ion conducting materials for developing high-performance inorganic all-solid-state ECDs.