News Coatings Technologies
Electrochromic polymers cut building energy demand by up to 25.7 %
Researchers have developed a series of conjugated polymers based on dibenzofuran, dibenzothiophene and carbazole units that switch reversibly from colourless to dark blue. Integrated into smart windows, one variant enables annual building energy savings of up to 25.7 % across diverse Chinese climate zones.
Electrochromic smart windows (ECSWs) are increasingly viewed as a tool for dynamically regulating solar radiation in buildings. Their development, however, has been limited by the difficulty of achieving high optical contrast between colourless and dark states while balancing further performance parameters. A recent study introduces a series of conjugated polymers based on dibenzofuran (DBF) or dibenzothiophene (DBT) combined with carbazole (Cz) units — designated DBT-Cz-6C, DBF-Cz-6C, DBT-Cz-Ph and DBF-Cz-Ph — designed to improve both structural stability and the range of accessible colours.
All four polymers showed strong electrochemical performance, switching reversibly from colourless to dark blue. The DBT-Cz-6C polymer stood out with an initial maximum transmittance of 90 % and only a 5 % transmittance loss after 1,000 switching cycles, indicating good long-term stability.
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Device performance and building energy simulation
DBT-Cz-6C was subsequently integrated into an electrochromic device (ECD) for more detailed characterisation. After 400 test cycles, transmittance decreased by only 2 %. The device exhibited coloration and bleaching times of 4.5 s and 4.9 s, respectively, values compatible with practical use in dynamic glazing systems.
To evaluate the technology’s impact under realistic conditions, the thermal management performance of the DBT-Cz-6C ECD was simulated with EnergyPlus using building models representing 20 cities across a range of climate zones in China. Buildings equipped with DBT-Cz-6C-based ECSWs achieved annual energy savings between 13.1 % and 25.7 %, primarily by reducing the cooling load through dynamic control of solar radiation. The authors conclude that the DBT/DBF-Cz conjugated polymer family holds significant potential for use in low-carbon and green building applications, offering a route to combine electrochromic functionality with meaningful energy savings.
Source: Ma, D. et al., Dibenzofuran/dibenzothiophene and carbazole based conjugated polymers for green building radiative cooling with the color changing from colorless to dark blue. Polym. Chem. 17, 3477–3485 (2026).
