Robust and stable dual-band electrochromic smart window with multicolor tunability

Dual-band electrochromic smart windows (DESWs) can selectively control the transmittance of near-infrared (NIR) and visible (VIS) light, which can significantly reduce building energy consumption. However, almost all the reported DESW colors switch between clear colorless and dark blue. The single color combined with the dazzling visual experience of blue will undoubtedly limit the application scene of DESWs. Herein, for the first time, we report a robust and stable DESW with multicolor conversion capabilities based on the single-component organic polymer polyaniline (PANI). The results show that the progressive electrochemical reaction enabled PANI film to deliver not only efficient and independent control of NIR and VIS light transmittance but also impressive electrochromic performance-rich color conversion (yellow-green-black), good optical modulation (65% at 633 nm and 59% at 1600 nm), high coloration efficiency (367.1 cm² C^-1 at 633 nm and 299.6 cm² C^-1 at 1600 nm), and excellent cycling stability (optical modulation losses of 6% at 633 nm, and 4% at 1600 nm after 10 000 cycles). Thereby, we demonstrated a prototype PANI-based DESW device (10 × 5 cm²), which delivered a multicolor electrochromism together with independent control and modulation of the VIS (sunlight) and NIR (solar heat) transmittance.