Perovskite capacitors offer change-sensitive retinomorpic sensors

Our eyes are more sensitive to movement than static imagery. By preprocessing visual stimuli to prioritize information about movement, the eye creates denser signals that can be processed more quickly by the brain. Cinthya Trujillo Herrera and John Labram propose a simple photosensitive capacitor inspired by this process.

Using a photosensitive perovskite, the researchers built a capacitor that changes capacitance in response to changes in illumination but not constant illumination. They characterized several sensors built with this design and simulated how arrays of these sensors would respond to optical stimuli.

“Most conventional optical sensors are designed to produce a signal when light is incident on them,” said Labram. “Our sensor is designed to operate in a fundamentally different way: it will only produce a signal upon changes in light intensity.”

In the capacitor, the perovskite semiconductor methylammonium lead iodide serves as a dielectric along with insulating silicon dioxide. Under constant illumination, the voltage across the capacitor is steady. However, when the level of illumination changes, the capacitance of the perovskite changes and causes a temporary spike in voltage across the capacitor.

The researchers characterize several fabricated capacitors to arrive at a general model, which they use to simulate an array of many sensors.

“Going from a brand-new device paradigm to a working array is almost certainly going to expose challenges we haven’t yet considered,” said Labram. Looking ahead, they plan to more precisely characterize their sensors, investigate other photosensitive dielectric materials, and implement a physical array of sensors.

Source: “A perovskite retinomorphic sensor,” by Cinthya Trujillo Herrera and John G. Labram, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0030097 .