Enhancing the Optical Response Speed of Thermochromic Paper Displays by Heat Exchange Manipulation of Invisible Heaters

Developing invisible heaters is critical to thermochromic paper displays for convenient and low power use. Maintaining high transmittance as well as uniform and widely adjustable resistance remains a challenge for quick and efficient heat exchange in paper displays. Here, through optimizing the spraying process parameters and the dynamic spraying path design on paper, highly uniform and continuously varied film sheet resistance is achieved. Through silver nanowire percolation control, the heat-transfer coefficient is manipulated from 20 to 40 W m^–2 K^–1. By directly printing high-resolution thermochromic patterns on the invisible heater side, fast and efficient heat transfer is achieved under a voltage lower than 9 V and benefits paper displays with a second-level optical response time and a power consumption below 30 mW cm^–2. Large chromatic aberration and discoloration speed are demonstrated from quantitative analysis of both static and dynamic reflection spectra. Guidance for designing thermochromic paper displays with fast response is provided.