Towards the design of ideal electrochromic materials with low driving voltage based on phthalate derivatives

Small molecular organic electrochromic materials have gradually attracted the attention from academia. Although ester organic electrochromic materials show unique advantages such as significant color change, wide color adjustment range and low cost, their electrochromic mechanisms are still unclear, keeping their driving voltage and stability issues unsolved. In this article, the absorption spectra of phthalate derivatives under different conditions are calculated with time-dependent density functional theory to understand the influences on the electrochromic properties by the electronic and steric effects. By the increased conjugation and reduced steric hindrance, carbonyl linking group is found capable to enhance the absorption in the visible region and exhibit low driving voltages. Further, a new electrochromic compound is designed to improve the luminous effect and lower the driving voltage.