Engineering Nanoscale Light-Heat Interactions in 2D Devices: Resolving Photovoltaic/Photothermoelectric Competition for High-Performance Optoelectronics

Abstract Title: Resolving competing light-to-electricity conversion mechanisms in nano-photodetectors for improved optoelectronic device performance Efficient photodetectors, essential components in technologies like telecommunications, medical imaging, and environmental monitoring, often face limitations due to competing electrical and thermal effects at very small scales. At the nanoscale, these two effects—the photovoltaic (PV) effect, where light directly generates electrical current, and the photothermoelectric (PTE) effect, where heat from light generates current—frequently interfere with each other, limiting the performance of devices such as cameras, sensors, and communication systems. This research aims to solve this fundamental problem by developing an advanced imaging method to precisely map and distinguish these effects at scales smaller than the wavelength of visible light. The outcomes of this research will significantly improve photodetector efficiency, enabling faster telecommunications, better medical diagnostics, and improved environmental sensing. Additionally, the project will support education and training for students through hands-on activities, workshops, and research experiences, preparing them for careers in rapidly evolving fields like nanotechnology and photonics. The technical objective of this research is to understand and control the interplay between PV and PTE effects in low-dimensional nanostructures to optimize photodetector performance. The research introduces a novel 3D Near-Field Scanning Photocurrent Microscopy (3D-NF-SPCM) method with sub-5 nm spatial resolution to disentangle these effects. The approach is organized into three synergistic research thrusts: (1) engineering thermal and Seebeck gradients in two-dimensional heterostructures (e.g., graphene/h-BN, carbon nanotube/MoS₂ hybrids) to systematically control PTE effects; (2) using nanoscale defects and strain gradients to decouple and coherently couple PV and PTE mechanisms, optimizing their combined response; and (3) integrating these nanoscale insights into real-world device architectures through plasmonic slot waveguides. The project will address current limitations in characterizing nanoscale optoelectronic properties, provide predictive design rules for high-performance photodetectors, and deepen fundamental understanding of nanoscale light-matter interactions. Results from this work will guide future developments in integrated optoelectronics, quantum sensing technologies, and nanoscale energy conversion systems. 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.