With large interstitial space volumes and fast ion diffusion pathways, amorphous metal oxides as cathodic intercalation materials for electrochromic devices have attracted attention. However, these incompact thin films normally suffer from two inevitable imperfections: self-deintercalation of guest ions and poor stability of the structure, which constitute a big obstacle toward the development of high-stable commercial applications. Here, we present a low-cost, eco-friendly hybrid cation 1,2-PG-AlCl3·6H2O electrolyte, in which the sputter-deposited a-WO3–x thin film can exhibit both the long-desired excellent open-circuit memory (>100 h, with zero optical loss) and super-long cycling lifetime (∼20,000 cycles, with 80% optical modulation), benefiting from the formation of unique Al-hydroxide-based solid electrolyte interphase during electrochromic operations. In addition, the optical absorption behaviors in a-WO3–x caused by host–guest interactions were elaborated. We demonstrated that the intervalence transfers are primarily via the “corner-sharing” related path (W5+ ↔ W6+) but not the “edge-sharing” related paths (W4+ ↔ W6+ and/or W4+ ↔ W5+), and the small polaron/electron transfers taking place at the W–O bond-breaking positions are not allowed. Our findings might provide in-depth insights into the nature of electrochromism and provide a significant step in the realization of more stable, more excellent electrochromic applications based on amorphous metal oxides.

The nanocrystal-in-glass (nanocrystals embedded amorphous matrix) tungsten oxide (WO 3 ) thin films with a nanoporous characteristic were prepared via an electron beam evaporation technique. The e-beam evaporated WO 3 thin films present a fast colored/bleached time of 16/11, 16/ 14, and 12/12 s, a large optical modulation of 92, 91, and 87% at 633 nm, and a high coloration efficiency of 61.78, 62.04, and 67.59 cm 2 C −1 in Li + , Na + , and Al 3+ electrolytes, respectively. On one hand, the improved electrochromic performance is mainly attributed to the short diffusion distance and buffering effect in the host matrix, which facilitates the ion insertion/ extraction and alleviates the structural collapse of the framework. On the other, owing to the strong electrostatic interactions between the trivalent cations and the host, the WO 3 thin films in Al 3+ possess a shallow diffusion depth and long cycle life. The individual contribution from the capacitance-or diffusion-controlled process is comprehensively demonstrated. Pseudocapacitive behavior in the nanocrystal-in-glass WO 3 thin films is in favor of fast kinetics response and sound cycling stability. Our work offers an in-depth insight of the electrochromic mechanism for nanocrystal-in-glass WO 3 thin films in various electrolytes and sheds light on the fundamental principle in the electrochromic devices.

As a kind of biocompatible material with long history, silk fibroin is one of the ideal platforms for on-skin and implantable electronic devices, especially for self-powered systems. In this work, to solve the intrinsic brittleness as well as poor chemical stability of pure silk fibroin film, mesoscopic doping of regenerated silk fibroin is introduced to promote the secondary structure transformation, resulting in huge improvement in mechanical flexibility (∼250% stretchable and 1000 bending cycles) and chemical stability (endure 100 °C and 3–11 pH). Based on such doped silk film (SF), a flexible, stretchable and fully bioabsorbable triboelectric nanogenerator (TENG) is developed to harvest biomechanical energy in vitro or in vivo for intelligent wireless communication, for example, such TENG can be attached on the fingers to intelligently control the electrochromic function of rearview mirrors, in which the transmittance can be easily adjusted by changing contact force or area. This robust TENG shows great potential application in intelligent vehicle, smart home and health care systems.