Electrochromic devices (ECDs) modulate their optical properties under the action of an electrical voltage [1]. While researchers have traditionally focused on improving reversibility, there is an emerging market for the development of visually irreversible ECDs. When integrated with appropriate sensors and probes, irreversible ECDs have potential applications in a broad range of commercial sectors, including monitoring, logistics, and transportation.

Herein, we present the development of a visually irreversible electrochromic indicator, based on the in-situ electrodeposition of 3,4-ethylenedioxythiophene in a flexible PET-ITO device. A ΔT > 80 % can be achieved with voltages as low as 2.5 V with coloration efficiencies greater than 20 cm2 C-1. Furthermore, the indicators are functional over a wide range of temperature from -20 ᵒC to 60 ᵒC, making them promising candidates for use in the cold chain market space.