Direct Chiro-Optical Detectors Based on Organic Semiconductors

University Of California-San Diego, La Jolla CA

Investigators

Abstract

Direct Chiro-Optical Detectors Based on Organic Semiconductors Detecting the polarization of light provides critical information for biological studies, quantum optics, environmental monitoring and navigation. However, current methods for sensing circularly polarized light (CPL) require bulky filters or complex plasmonic nanostructures that preclude miniaturization and scalable fabrication of CPL detectors. To overcome these shortcomings, this project aims to create novel devices using chiral organic semiconductors that provide the transformative capability to directly capture CPL characteristics. The research will clarify fundamental mechanisms that dictate polarization response in chiral semiconductors and use the new insights to realize compact, low-cost devices that can vastly expand implementations of polarization-sensitive detectors. The rich polarization information will empower new analyses in scientific, medical, industrial, and defense applications. This project will incorporate outreach activities, including the development of new workshop materials for summer programs and science kits for K-12 students. This project will study new device architectures to determine design guidelines for amplifying the chiro-optical response of organic semiconductors. While chiral organic semiconductors have shown strong chiro-optical response, the origins of the dissymmetric interactions with CPL are still not fully understood, particularly with respect to the contributions from mesoscopic designs. Thus the goal of this proposal is to explain the fundamental effects of mesoscopic ordering on chiro-optical response and increase the semiconductor sensitivity and selectivity to a target CPL handedness. Here the proposed approach is to use a bilayer junction which decouples the photogeneration and charge transport processes so that the chiral absorber and the transport layer can be independently optimized. In the first project objective, (1) the electronic interactions between the organic chiral absorber and the oxide transport semiconductors will be manipulated to facilitate charge injection and trigger photomultiplication to significantly raise sensor detectivity. Next, (2) the sensor selectivity to the CPL handedness will be enhanced by assembling chiral mesoscopic structures for the absorber layer. Through custom electrospinning techniques, the structural parameters can be modified precisely to identify factors that hinder the device performance from reaching the theoretical dissymmetry limit. For the third objective, (3) the integration of linearly and circularly polarized devices into a super-pixel will provide complementary signals that are crucial for extracting sub-surface features and improving depth resolution of back-scattered light measurements. The expected project outcome is to gain foundational knowledge clarifying the structure-property-processing relations for chiral organic semiconductors, so this class of materials can be engineered into portable, affordable CPL detectors to harness the rich opportunities in polarization-sensitive applications. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.