Polymer matrix-mediated nanowire networks and photonic structures for high-sensitivity near-infrared phototransistors

High-sensitivity near-infrared (NIR) photodetectors are crucial for applications in thermal imaging, night-vision and wellness monitoring. In comparison to the conventional technology based on inorganic semiconductors, organic phototransistors (OPTs) offer a promising alternative due to their low cost, flexible design, adaptability to various fabrications, and large area manufacturability. However, several key issues remain to be addressed, namely, the low field-effect mobility and limited NIR light absorption. One way to circumvent this hurdle is to create an organic channel film with ordered structure for mobility enhancement and a special device design to increase its NIR light absorption. Various approaches have taken this route, such as incorporating metal nanoparticles, surface plasmonic structures and a bulk heterojunction in the channel layer in OPTs. Yet all had only limited success due to technical challenges. In this application, we propose two novel approaches to alleviate this barrier: (1) to achieve high charge transport efficiency by controlling the crystalline order of the organic channel layer, (2) to incorporate photonic structures in OPTs to realize NIR light absorption enhancement by coupling with the waveguide modes in the organic channel layer. Comprehensive and systematic research on NIR OPTs, based on matrix-mediated nanowire networks of NIR-absorbing conjugate polymers and integration with organic photonic structures, is rather rare. This project utilizes a synergistic approach of theoretical simulation, experimental optimization as well as nanostructure analysis and process integration. The objective is to realize high-sensitivity, solution-processed NIR OPTs through controlling the nanostructures of the polymer channel film with improved charge transport and enhanced NIR light absorption