Operating principles of zero-bias retinomorphic sensors

Abstract

Zero bias retinomorphic sensors (ZBRSs) are a new type of optical sensor which produce a signal in response to changes in light intensity, but not to constant illumination. For this reason, they are hoped to enable much faster identification of moving objects than conventional sensing strategies. While recent proof-of-principle experimental demonstrations are significant, there does not yet exist a robust quantitative model for their behaviour, which represents an impediment for effective progress to be made in this field. Here I report a mathematical framework to quantify and predict the behaviour of ZRBSs. A simple device-level model and a more detailed carrier-dynamics model are derived. Both models are tested computationally, yielding equivalent behaviour consistent with experimental observations. A figure of merit, Λ_0, was identified which is hoped to enable facile comparison of devices between different research groups. This work is hoped to serve as the foundation for a consistent description of ZBRSs.

Transient On/Off Photocurrent Response of Halide Perovskite Photodetectors

“…This model gives insight into the dominant features of the transient signals of voltage and current, and it enables a classification of responses in terms of a few key parameters. More detailed models based on specific polarization and charge collection mechanisms can be applied to understand each of the main capacitive, transport, and inductive properties …”

“…More detailed models based on specific polarization and charge collection mechanisms can be applied to understand each of the main capacitive, transport, and inductive properties. 49…”

“…Recent works on PDs explain the origin of the initial peak well in terms of capacitive effects. These photocharging features can be due, for example, to the separation of electron and hole distributions in organic semiconductors. ,− It is well-known that the capacitance in halide perovskite measured by impedance spectroscopy is a strong function of incident light and shows very large values. − As mentioned before, in perovskite PDs, it has been observed that the large capacitance has a predominant effect. , For simplicity, we describe the capacitive effect with a simple constant capacitor C m that represents the low-frequency capacitance of the device. The transient dependence of the capacitance on light is ignored in the first approximation.…”

Retinomorphic Motion Detector Fabricated with Organic Infrared Semiconductors

“…In summary, this work has offered key design guidelines to improve the exciting retinomorphic technology. While there are questions remaining such as the asymmetric response [12] of the sensor during switching, it may be a powerful combination in the future to integrate organic retinomorphic sensors with a neuromorphic processor, to finally meet the requirements for implementing real-time machine learning in navigation and imaging diagnostic applications. The acceptor [6,6]-phenyl-C71-butyric acid methyl ester (PC 70 BM) was purchased from Ossila Ltd.…”

“…A class of thin‐film retinomorphic sensors with a capacitor‐resistor design [ 7 , 8 ] allows a simpler, higher density implementation than prior silicon‐based circuits [ 9 ] and makes them well suited for low‐power, high‐speed identification of moving objects, complementary to other bioinspired phototransistor structures. [ 10 , 11 ] While a series of insightful papers by Labram [ 12 , 13 , 14 , 15 ] have discussed device models and basic operating principles, the development of thin‐film retinomorphic devices is nascent and many critical aspects have yet to be explored.…”