Bhattacharjee, Saheli and Kundu, Susmita and Ghosh, Srabanti and Pramanik, Jishu (2025) Polymorphic Phase Junction Engineering in WO(3-x) for High Performance Electrochromic Smart Windows. In: Materials Research Society of India (Kolkata Chapter), 8 Aug 2025, Indian Association for the Cultivation of Science.

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Abstract

The building sector is responsible for about 15% of global CO2 emissions and nearly a third of the world's energy use, mainly because of heating and cooling systems. Tungsten oxide based electrochromic smart windows offer a clever way to cut this energy demand, as they can change color and control light transmission with a small external voltage [1.2]. Yet, practical use has been limited by the material's inherent shortcomings, such as, suboptimal optical modulation and compromised electrochemical stability due to solid electrolyte interface (SEI) formation. To overcome these challenges, we have developed a unique hexagonal-monoclinic WO(3-x) phase junction by carefully adjusting the dwelling time during hydrothermal synthesis. Our analysis showed that keeping the material at the optimal dwelling time of 12 hours created a balanced mix of both phases (m/h = 0.71). This mixed-phase material demonstrated impressive electrochromic performance: an optical modulation of 88±3%, fast switching speeds (coloration in about 0.49 s and bleaching in 0.39 s), and excellent cycling stability retaining performance Over 5000 redox cycles with only ~7% loss in reversibility. Remarkably, this is the first time such stable coexistence of hexagonal and monoclinic phases has been achieved in sub-stoichiometric WO(3-x), adding a new dimension to electrochromic research. Further tests revealed the mixed-phase material had a much higher donor density. enabling stronger redox reactions. By engineering this phase junction, we unlocked better charge transfer and electrochemical robustness, paving the way for advanced smart windows. These could help buildings to manage heat and light more efficiently, ultimately reducing energy consumption and supporting a greener, low-carbon future.

Item Type:	Conference or Workshop Item (Poster)
Subjects:	Engineering Materials
Divisions:	Sensor and Actuator
Depositing User:	Ms Upasana Sahu
Date Deposited:	12 May 2026 16:50
Last Modified:	12 May 2026 16:50
URI:	https://cgcri.csircentral.net/id/eprint/5785

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