Multicolor and multistable transparent electrochromic materials and displays

Electrochromic (EC) displays attract growing interest as promising candidates for next-generation transparent displays due to their intrinsic high transmittance and excellent eye-friendly properties. However, achieving simultaneous high transparency and vivid multicolor switching remains challenging. Here, we present a single-molecule design strategy that integrates a rhodamine moiety with a ProDOT (3,4-propylenedioxythiophene) unit. Following systematic screening of molecular dopants, these systems demonstrate well-matched electrochemical potential windows and compatible redox behaviors, thereby effectively eliminating color interference. The as-prepared PTRh-B devices achieve high optical transmittance with three distinct optical states—colorless, magenta, and blue—and multiple stable states (colorless and blue states >5 h; magenta state >30 days). The devices also show excellent cycling stability of over 5,200 cycles for the colorless-to-magenta and 8,400 cycles for magenta-to-blue transitions, coupled with fast switching times of 0.13 s and 1.8 s, respectively. Moreover, functional pixel-level display is successfully realized, underscoring the significant potential for developing advanced transparent and energy-efficient display and electronic erasable memory systems. To achieve simultaneous transparency and vivid multicolor switching in electrochromics is desirable owing to their potential as next-generation transparent displays. Here, the authors show a single-molecule design strategy that integrates a rhodamine moiety with a propylenedioxythiophene unit and incorporates molecular doping to achieve high optical transmittance with three distinct optical states.