The material is an organic photovoltaic semiconductor (called rr-P3HT) which, unlike the metal or silicon-based materials used until now for such biotechnological interfaces, is soft, light, flexible and highly biocompatible and naturally sensitive to visible light.
Other research projects in the field of artificial retinas are currently focusing on carbon-based materials like nanocrystalline diamond and graphene, but those are intended for replacing silicon electrodes, like the Argus 2.
To be sure, increasingly capacious chemistry and materials are used to improve the capabilities of batteries such as switching from carbon-based anodes to silicon-based ones.