Achieving the gray to transparent switching electrochromic properties based on the diketopyrrolopyrrole, 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene units

Electrochromic (EC) technology has attracted increasing attentions owing to their numerous advantages and extensive prospects. Here, the classic donor-acceptor (D-A) strategy was employed to design and synthesize three soluble polymers PTPD-1, PTPD-2, and PTPD-3, which was compatible with the current extensive requirements in the fields of EC conjugated polymers. Thereinto, diketopyrrolopyrrole was used as acceptor, 3,4-propylenedioxythiophene and thieno[3,2-b]thiophene were employed as donors. The influence of different feed ratios between donors and acceptors on the electrochemical, optical and EC performance of the three polymers were investigated in detail. The three polymers possess low oxidation potentials and optical band gaps (lower than 1.4 eV), and demonstrate different colors in the p-type doping process including greyish-green/dark gray/transparent color (PTPD-1), dark gray/gray/transparent color (PTPD-2) and green/light gray/transparent color (PTPD-3). Furthermore, all the three polymers show high optical contrasts (beyond 70% in the near infrared region), fast switching time and satisfying coloration efficiency. In conclusion, this study supplies a new structural design for the EC polymers switching between gray and transparent color, and can be beneficial to understand the EC behaviors of the D-A type conjugated polymers based on the DPP units.

Automated summary

Electrochromic technology has gained significant attention due to its advantages and prospects. In this study, three soluble polymers were designed and synthesized using the donor-acceptor strategy, which exhibited favorable electrochemical, optical, and EC performance. The polymers showed the ability to switch between gray and transparent colors, with high optical contrasts and fast switching times.