A polymer/fullerene based photodetector with extremely low dark current for x-ray medical imaging applications

Organic photodetectors for use in medical x-ray digital imaging applications are fabricated from poly(3-hexylthiophene) and [6,6]-phenyl $C61$-butyric acid methyl ester using a solution-based, temperature assisted deposition protocol. In comparison to bulk heterojunction structures, the proposed protocol leads to much lower dark currents while still offering useful external quantum efficiency values. Devices made by this protocol lead to dark currents of around $50pA∕cm2$ at $−0.8V$⁠, well within the requirements for x-ray digital imaging. When coupled to a scintillating phosphor screen the device yields a linear response of photocurrent to x-ray exposure (from $0to7mGy∕s$⁠) for a range of operating biases.