Photo-electrochromic thin films based on charge trapping and release mechanism

Stimuli-responsive or "smart" materials change their physical or chemical properties when an external stimulus is applied, including stress, moisture, pH, magnetic field, light etc. These class of materials are the core technology of a wide range of applications, from sensors to novel optoelectronic devices.

Photo-electrochromic materials change their optical properties in response to light and electric field. In our research, we explore the electron transport behavior of metallo-organic films on transparent conductive oxides. In particular, we study charge trapping and release facilitated both by light and electrochemistry.¹ The amount of charge stored in the films is directlty correlated with the intensity of the color of the material.

Our molecular assemblies consist of two redox-active layers of ruthenium and iron complexes. The layers of ruthenium complexes are bound to the metal oxide electrode and mediate the electron transport between the electrode and the distant layer of iron complexes. Photoexcitation of the ruthenium complexes changes their redox properties and allows the release of the charge stored in the layer of iron complexes.