Fig. 2: Detailed working principles of dark-current-shunting (DCS) X-ray detector.

a Working principle at the dark condition and with DCS electrode disabled. The electrons emitted from the source transport through the conduction channel, and are collected by the drain, the DCS detector is working in a two-terminal mode similar as a photoconductive detector. b Working principle at the dark condition and with DCS electrode applied with a small bias. Some electrons emitted from the source are attracted by the DCS electrode, and the drain collects fewer electrons than the case described in Fig. 2a, leading to a smaller dark current. c Working principle at the dark condition and with DCS electrode applied with a CV. The electrons emitted from the source are all attracted by the DCS electrode, and the drain will not receive any electrons, leading to zero dark current in principle. d Working principle at the dark condition and with DCS electrode applied with a bias larger than CV. Some electrons are extracted from the drain and collected by the DCS electrode, leading to a negative dark current. e Working principle at X-ray illumination and with DCS electrode disabled. The DCS detector is working in a two-terminal mode similarly as the photoconduction detector. f Working principle at X-ray illumination and with DCS electrode applied with a CV. In order to minimize the dark current, the DCS electrode should be biased with a CV. Under X-ray excitation, the photo-generated excess carriers are transported through the transport layer (ETL) and sensitize the conduction channel, eventually producing photocurrent at the drain (Source electrode is always contacted to the ground, drain electrode is applied with a working voltage. Working voltage and CV here are positive).