Three-Dimensional Integration of Switching and Light-Sensitive Organic Transistors in Solution Processes for Flexible High-Resolution Active-Matrix Optical Imager

A three-dimensional (3D) integration architecture composed of a top-gate organic thin-film transistor (OTFT) as pixel switch and a bottom-gate organic phototransistor (OPT) for photo-sensing is proposed to construct flexible active-matrix optical imager. The two devices in one pixel can be separately optimized for functions of pixel switching and photo-sensing, respectively. Low temperature ( $ < 150 ^{\circ }$ ) solution-based integration processes are developed to achieve high-resolution 3D stacking on plastic substrate. A flexible active-matrix imager of ${100}\times {100}$ pixels (127 ppi) is implemented based on such integration architecture, and demonstrated for fingerprint imaging under ambient light condition.