Organic photoconductive film-stacked active pixel sensor pixel circuits using indium-tin-zinc-oxide thin-film transistors

In this study, we describe the signal readout capabilities of indium-tin-zinc-oxide (ITZO) thin-film transistor (TFT)-based active pixel sensor (APS) pixel circuits combined with organic photoconductive films (OPFs). A pixel circuit was fabricated with a size of 50 mu m containing three ITZO TFTs having a channel length of 2 mu m and a blue-sensitive OPF possessing excellent properties with an external quantum efficiency of similar to 59% and a dark current density of <100 pA cm(-2). Signal readout operation of the pixel circuits in accordance with irradiated light intensity was demonstrated, and sufficient response speeds within the line selection period, assuming a pixel number of 320 x 240 (QVGA) at 60 frames per second (similar to 69.4 mu s), was also confirmed by fabricating pixel line arrays comprising 320 and 240 pixels. Our findings show that the miniaturized ITZO TFTs have potential for use in high-pixel-density TFT-based APS image sensors with improved imaging quality.