Pixel-less and Pixel-lated Inorganic/Organic Hybrid Infrared Imaging Upconversion Devices

Abstract

Nowadays, the industrial standard for infrared imaging systems is to interconnect an infrared photodetector array with a silicon-based read-out-integrated circuit pixel by pixel through existing indium bumping technology for infrared scene detection and then the signal is output optically through a LCD or other imaging devices. Motivated by the high-cost and low-resolution of such configurations, technology that up-converts infrared light to visible light and in particular, an inorganic/organic hybrid imaging upconverter has been developed. The end goal was to provide a high-efficiency and high-resolution alternative for infrared imaging. The inorganic/organic hybrid architecture takes advantage of both the high quantum efficiency of photo-detection for inorganic semiconductors, and the low-cost processing and the topologically perfect structure of organic semiconductors that does not require lattice matching for materials. Based on previous single-element hybrid infrared upconverter designs, both pixel-less and pixel-lated hybrid infrared imaging devices are presented, with experimental results, in this thesis. The pixel-less hybrid infrared imaging upconverter suppresses the lateral carrier diffusion by using a hybrid Schottky junction with an intrinsic interconnection layer between the inorganic and organic parts. The device was fabricated in one large-area mesa and proved that the emitting light spatially correlated with the infrared imaging shone at its back. This device is the first-ever hybrid pixel-less infrared upconverter to successfully demonstrate the imaging of infrared patterns. In contrast, the pixel-lated device consisted of 128 by 128 pixels, and each pixel was an individually working infrared upconverter that integrated a heterojunction phototransistor (HPT) and an organic light emitting diode (OLED). The HPT provides not only the photoresponse upon incoming infrared light but also an amplification of the photocurrent. The pixel-lated device also successfully demonstrated the first-ever upconversion of infrared light, up-converting a light with a wavelength of 1.5 μm to 520 nm.