Highly Transparent ITO/HfO₂/ITO Device for Visible-Light Sensing

Transparent visible-light sensors are of critical importance in invisible optoelectronic circuits as the interface between the optical and electrical domains. However, devices designed based on photocarrier generation for light sensing limit the transparency of the device in the visible region, as the optically active layer also passively absorbs light continuously. In this work, we present an all-transparent ITO/HfO2/ITO device with the wide bandgap HfO2 functioning as the resistive switching and the light sensing element. Electrically switching the resistive state of the device to a low-resistance soft-breakdown state is demonstrated to cause the wide-bandgap visible-light blind HfO2 to become photoresponsive. This allows us to optically functionalize the device for an optical response by electrical breakdown in the oxide and can be triggered on-demand. Apart from the on-demand optical response in the device, the inherent resistive switching properties of the HfO2 device allow for integration of memory and optical sensing capabilities, presenting a novel phenomenon for optical sensing in invisible optoelectronics.