Co(II)-Based Metallo-Supramolecular Polymer with Thiazolo[5,4-d]Thiazole Spacer: Dual Band Vis-to-NIR Electrochromic Smart Window for Solar Irradiance Modulation

Visible-to-NIR dual-band electrochromism has been widely applied in smart windows to reduce energy consumption for indoor cooling, contributing to green building development. In this context, we have designed and synthesized a Co(II)-based metallo-supramolecular polymer (Co-TPYTZTPY) incorporating a conductive thiazolo[5,4-d]thiazole spacer. The polymer was comprehensively characterized using various spectroscopic techniques, morphological analyses, and electrochemical studies. The Co-TPYTZTPY film exhibited reversible yellow to deep blackish-brown electrochromism in the NIR region in both aqueous and nonaqueous electrolytes. Notably, the film demonstrated superior durability and electrochromic performance in nonaqueous media, attributed to the absence of competing catalytic hydrogen evolution reactions. Furthermore, we fabricated, for the first time, a quasi-solid-state electrochromic device with dimensions of 6.5 × 2.5 cm², based on a Co(II)-metallo-supramolecular polymer. This device exhibited robust electrochromic stability over 1000 cycles, faster response times, and lower energy consumption compared to conventional display devices. In its reduced blackish-brown state, the device effectively blocked 68% of total solar irradiance. A prototype demonstration for solar heat modulation showed a ∼10 °C temperature difference between the neutral and reduced states, highlighting the potential of Co-TPYTZTPY for smart window applications.