Stacked organic photoconductive films and thin-film transistor circuits separated by thin silicon nitride for a color image sensor

We develop a color image sensor with three stacked organic photoconductive films (OPFs) sensitive to only one primary color component (red (R), green (G), or blue (B)); each OPF has a signal readout circuit. This type of stacked image sensor enables a small color camera to achieve high picture quality, because color-separation systems, such as color filter arrays, are eliminated. Previously, we demonstrated green, red, and yellow color images reproduced from a sensor with two stacked OPFs sensitive to the R or G component by applying In-Ga-Zn-O thin film transistor (IGZO TFT) circuits separated by a 10-μm-thick epoxy film as an interlayer insulator. In this study, we first improve the configuration of the IGZO TFT to reduce the compressive stress that causes the films to peel off and break the stacked structure. Then, we fabricate a structure with three stacked OPFs sensitive to the R, G, or B component with a thickness of 5.8 μm by using 2-μm-thick silicon nitrides as interlayer insulators.