Thin-film image sensors with a pinned photodiode structure

Abstract

Organic semiconductor and colloidal quantum-dot-based thin-film image sensors show reduced noise, dark current and image lag when a pinned photodiode pixel structure, similar to those in silicon-based image sensors, is used. Image sensors made using silicon complementary metal-oxide-semiconductor technology can be found in numerous electronic devices and typically rely on pinned photodiode structures. Photodiodes based on thin films can have a high absorption coefficient and a wider wavelength range than silicon devices. However, their use in image sensors has been limited by high kTC noise, dark current and image lag. Here we show that thin-film-based image sensors with a pinned photodiode structure can have comparable noise performance to a silicon pinned photodiode pixel. We integrate either a visible-to-near-infrared organic photodiode or a short-wave infrared colloidal quantum dot photodiode with a thin-film transistor and silicon readout circuitry. The thin-film pinned photodiode structures exhibit low kTC noise, suppressed dark current, high full-well capacity and high electron-to-voltage conversion gain, as well as preserving the benefits of the thin-film materials. An image sensor based on the organic absorber has a quantum efficiency of 54% at 940 nm and read noise of 6.1e(-).