Design and fabrication of dual electrochromic device with broader color space

Narrow color spectrum is a major limitation of the conventional electrochromic devices (ECDs) having a single electrochromic polymer (ECP) layer. Here, we report the design and fabrication of dual ECD capable of displaying a broader color spectrum at different voltages. The ECD color depends on the energy band gap of the ECP layer. Thus, it is possible to broaden the accessible color space by combining two (or more) ECPs in a single ECD. We have designed and fabricated dual ECD using two ECPs, polyaniline (PANI) and poly(3-hexyl thiophene) (P3HT). The dual ECDs show a wider color spectrum in comparison to the ECD prepared with either PANI or P3HT layer. Experimental measurements show that the complementary dual ECD (gel electrolyte is sandwiched between two ECPs) shows a much broader color range than hybrid dual ECD (both ECP layers on one side of gel electrolyte). The color space of complementary ECD is found to be a function of the viewing side. Moreover, the hybrid arrangement of ECP layers adds a new shade to the color spectrum accessible to complementary dual ECD. A combination of these ECDs may be used to design displays with varying color ranges and color intensity.