High‐Performance Reflective Electrochromic Device by Integrating White Reflector and High Optical Density Electrochromic System

Abstract This paper reports an efficient reflective electrochromic device (ECD) by integrating a highly reflective micro‐porous titanium dioxide–based white reflector film and an optimized transparent to black convertible electrochromic (EC) system. This reflective ECD can reflect almost 58.5% of light in the white state and 4.7% in the dark black state at 550 nm. Similarly, it also exhibits a very high ambient contrast ratio of 38:1 under office ambient light condition and good driving stability of about 83% in the white state (0 V) and 98% in the black state (1.7 V) after 10 000 driving cycles. In addition, the EC system is optimized by selecting good proton generator and suitable solvent for better coloration property as well as a low driving voltage via lactone ring opening reaction of leuco dye and supporting polymer for high optical density through suppressing the movement of oxidized leuco dye to the electrode. An ECD with the optimized EC system shows significant improvement in average optical density from 0.62 to 1.9 (at 400 to 700 nm) and faster switching speeds of about 1.6 s.