Collaborative Research: Nanostructured Conductive Tin Oxide for High-Efficiency Light Trapping in Thin Films and Photonic Devices

该项目由材料研究部(DMR)的电子和光子材料计划(EPM)和电气、通信和网络系统(ECCS)的电子、光子学和磁性设备计划(EPMD)共同资助。非技术描述：本项目研究纳米导电二氧化锡作为自组装电极在基于薄膜和二维(2D)材料的光子器件中的高效捕光。这些纳米结构将入射光散射到有源吸收材料的平面上，从而将光捕获到超薄吸收材料中，从而大大增强了光的吸收。与基于晶片的光电子器件相比，这项技术可以大幅降低材料消耗和成本。它具有广泛的潜在应用，从红外传感/成像到能量采集，包括直接将热能转化为电能。超薄吸收体中的光陷阱还使一组新的灵活、高效的光子器件能够安装在曲面上。该项目为研究生和本科生提供了广泛的尖端研究经验。该团队还参加了波士顿科学博物馆的“共享科学工作坊和实践”，以演示捕光效果，使参观者能够用肉眼观察原子薄的石墨烯层。PI(刘)将这个研究项目产生的新概念整合到达特茅斯学院为高三和高年级学生举办的夏季工程研讨会中。Co-Pi(Kong)参与麻省理工学院埃杰顿中心，鼓励K-12年级的学生使用研究中生产的纳米结构材料。技术描述：该项目研究高效率、低损耗的光子器件中的光捕获。目的是研究纳米导电氧化锡SnOx(X2)作为一种低温(250摄氏度)自组装电极，用于薄膜和基于2D材料的光子器件中的有效光捕获，从而大大提高其量子效率。由于非化学计量比，过剩的锡在退火时偏析，并导致纳米砖/纳米针的形成。为了实现高的光捕获效率，该团队研究了SnOx和薄膜/2D吸收材料之间的纳米结构形成、双极电导和纳米级光学耦合的基本原理。基于通过该项目获得的新知识，可以针对不同的应用优化器件结构和制造工艺。两个例子是(A)用于热光电池和红外传感器的Ge和GeSn薄膜中SnOx增强的光陷阱，以及(B)用于光子器件的SnOx/2D材料异质结。这项研究可能会导致一种新的低损耗、纳米结构的导电氧化物，用于在厚度从单原子层到几微米的薄型有源吸收体中高效捕光。与传统的表面织构透明导电氧化物相比，这种新技术提高了超薄吸收材料的捕光效率，同时最大限度地降低了表面泄漏电流。

This project is jointly funded by the Electronic and Photonic Materials Program (EPM) in the Division of Materials Research (DMR), and by the Electronics, Photonics, and Magnetic Devices Program (EPMD) in the Division of Electrical, Communications and Cyber Systems (ECCS). Nontechnical Description: This project investigates nanostructured conductive tin oxide as a self-assembled electrode for high-efficiency light trapping in photonic devices based on thin films and two-dimensional (2D) materials. These nanostructures scatter the incident light into the plane of the active absorber materials, thereby "trapping" the light for strongly enhanced optical absorption in ultrathin absorbers. This technology enables a drastic reduction in materials consumption and cost compared to wafer-based optoelectronic devices. It has broad potential applications from infrared sensing/imaging to energy harvesting, including direct conversion of heat into electricity. The light trapping in ultrathin absorbers also enables a new group of flexible, high-efficiency photonic devices that can be installed on curved surfaces. The project provides a broad range of cutting-edge research experiences for graduate and undergraduate students. The team also participates in the "sharing science workshop and practicum" at the Museum of Science in Boston to make demos on the light trapping effect that allows visitors to observe an atomically thin graphene layer with naked eyes. The PI (Liu) integrates the new concepts generated from this research project into the Summer Engineering Workshop at Dartmouth College for high-school juniors and seniors. The Co-PI (Kong) participates in the MIT Edgerton Center to inspire K-12 students using the nanostructured materials produced in the research.Technical Description: This project studies high-efficiency, low-loss light trapping in photonic devices. The goal is to investigate nanostructured conductive tin oxide SnOx (x2) as a low-temperature (250 degrees Celsius) self-assembled electrode for efficient light trapping in thin-film and 2D-materials based photonic devices, thereby greatly enhancing their quantum efficiencies. Due to the non-stoichiometry, the excess Sn segregates upon annealing and induces nanobrick/nanoneedle formation. In order to achieve high light trapping efficiency, the team studies the fundamentals of the nanostructure formation, ambipolar electrical conduction, and nanoscale optical coupling between SnOx and thin film/2D absorbers. Based on the new knowledge gained through this project, the device structure and fabrication process can be optimized for different applications. Two examples are (a) SnOx enhanced light trapping in Ge and GeSn thin films for thermo photovoltaic cells and infrared sensors, and (b) SnOx/2D material heterostructures for photonic devices. The research can potentially lead to a new class of low-loss, nanostructured conductive oxides for high efficiency light trapping in thin active absorbers with thicknesses ranging from a single atomic layer to a few micrometers. Compared to conventional surface-textured transparent conductive oxides, this new technology enhances light trapping efficiency for ultrathin absorbers and minimizes the surface leakage current simultaneously.