Polythieno[3,4-b]thiophene as an Optically Transparent Ion-Storage Layer

Ion storage layers have been employed in the construction of electrochromic devices to enhance device lifetimes through balanced ion shuttling. This has led to a search for a material which has a high charge capacity as well as optical transparency. Poly(thieno[3,4-b]thiophene) (PT34bT) exhibits high transparency in the visible region in both its neutral and oxidized states, in addition to having a high charge capacity, making it an ideal candidate for an ion storage layer. Herein we report devices fabricated by electrodeposition of several common chromophores, such as PEDOT, PDiBz-ProDOT, and PProDOT-Me-2. Devices were made with and without a balanced layer of PT34bT on the counter electrode and were probed for coloration and contrast. It was found that the addition of the ion storage layer did not alter the color of any of the devices and resulted in a minimal, predicted loss of contrast corresponding to the thickness of the ion storage layer.