Solution-processed image sensors on flexible substrates

Abstract

Image sensors are ubiquitous and used in a wide variety of applications ranging from consumer products to healthcare and industrial applications. The signal-to-noise ratio (SNR) of an image increases with larger pixels, which is costly to scale using silicon and wafer-based microfabrication. On the other hand, the performance of solution-processed photodetectors and transistors is advancing considerably. The printability of these devices on plastic substrates can enable low-cost scaling of large-pixel, high SNR image sensors. In addition, the flexibility of the substrates can enable new imaging systems never possible with the rigidity of conventional sensors. In this work we review the progress made towards solution-processed image sensors on flexible substrates. The fundamental operation of image sensors using intra-pixel charge integration is first explained to introduce the figures of merit for these systems. The physics, figures of merit, and state of the art for solution-processed photodiodes and phototransistors is also overviewed. A literature survey is done on solution-processed passive and active pixel image sensors with emphasis on active-switching for intra-pixel charge integration. Finally, optics compliant with large area and flexible image sensors are reviewed.