Sustainable dual-response optical modulation: WO3-based transparent cellulose composite membrane for photo- and electro-responsive chromatic devices

Abstract

Photo- and electro-chromic devices can facilitate the realization of a wide set of future applications, ranging from transparent displays, dynamic windows, optical switches, and variable optical attenuators. Tungsten oxide (WO₃) has always been the most studied material in the field of photo- and electro-chromic, although it has some bottlenecks. Here, we report a flexible transparent wood membrane for photo- and electro-chromic applications. The photochromic membrane (PCM) shows excellent photochromic properties, including high optical modulation (ΔT_{1030 nm} = 68.8%), ultraviolet (UV) shielding (>92%) and dynamic light regulation. Meanwhile, the electrochromic membrane (ECM, active area: 1 cm × 2.5 cm) and assembled complementary devices (active area: 3.4 cm × 3.4 cm) produce high optical modulation (ΔT_{1030 nm} = 78.2%) at 1030 nm, and the transmittance in colored state of below 10%. Noteworthy, the ECM (active area: 3.4 cm × 3.4 cm) comprised of WO₃/Ag nanowires (NWs)/flexible wood-derived transparent cellulose membranes, reveals enhanced optical modulation (60.7%) and rapid response time (coloring/bleaching time: 7.6 s/10.8 s). Moreover, the electrode also presents good cycling stability (96.2% after 120 cycles). The design of these chromic devices introduces an innovative strategy, which is expected to open up a new way for the development of photo- and electro-chromic devices. Crucially, the inherent flexibility and scalability of the transparent wooden substrate enable it to maintain relatively stable performance across different device dimensions, thereby resolving practical challenges in real-world applications.