Photophysics of Intraband Transitions in n-type Colloidal Quantum Dots

非技术描述：该项目致力于由半导体纳米晶体制成的新材料的制备和研究，这些材料可以探测温暖物体发出的热量。热红外线技术的潜在应用例子包括自动驾驶车辆的快速避让传感器、特定温室气体排放的传感以及通过大气层进行眼睛安全的高带宽光学通信。然而，红外线设备在这些类型的应用中的广泛使用受到当前技术非常高的成本的限制。该项目的重点是半导体量子点。这种新的材料方法可能会彻底改变中红外线技术在我们日常生活中的可及性，用于安全、监测、通信、健康和污染监测。该项目支持对新型量子点的合成和性能测试的研究。此外，该研究还为研究生提供了物理和化学方面的高级培训机会，同时还支持相关的推广活动。技术描述：最近的研究表明，电子掺杂的胶体量子点在3-12微米的中红外波段表现出强烈的光学响应，并具有中红外光电探测器和发射器的功能。红外响应来自两个最低电子态之间的带内光学跃迁，而波长可根据粒子的大小进行调节。该项目通过可调和稳定的掺杂扩大了电子掺杂量子点材料的范围，包括氧化物和硫系化合物。同时，中红外激光研究使测量不同材料的光物理性质成为可能。研究了量子产率随波长、材料、配体、温度和周围基质的变化，以了解和减少非辐射过程。泵浦-探测研究解决了俄歇复合动力学。时间分辨光谱学可以测量声子的耦合和均匀的线宽。这个项目定义了这些n掺杂胶体量子点的可能性质的物理边界，从而揭示了这些新的红外发色团可以在多大程度上改变红外技术。

Nontechnical description: This project addresses the preparation and investigation of new materials made of semiconductor nanocrystals that can detect heat emitted by warm objects. Examples of potential applications of thermal infrared technologies are rapid avoidance sensors of people for self-driving vehicles, sensing of specific greenhouse gas emissions, and eye-safe high-bandwidth optical communications through the atmosphere. However, the widespread use of infrared devices in these types of applications is limited by the very high cost of the current technologies. The focus of the project is on semiconductor quantum dots. The new material approach may completely transform the accessibility of mid-infrared technologies in our daily life for safety, surveillance, communication, health and pollution monitoring. The project supports research on the synthesis of novel quantum dots and the testing of their properties. In addition, the research offers advanced training opportunities for graduate students in physics and chemistry, while also supporting related outreach activities.Technical description: It has been recently shown that electron-doped colloidal quantum dots exhibit strong optical response in the mid-infrared from 3-12 microns and function as mid-infrared photodetectors and emitters. The infrared response arises from the intraband optical transition between the two lowest electron states, while the wavelength is tunable by the size of the particle. The project expands the range of electron-doped quantum dot materials with tunable and stable doping, including oxides and chalcogenides. In parallel, laser studies in the mid-infrared enable the measurements of the photophysical properties of the different materials. Studies of the quantum yield as a function of wavelength, materials, ligands, temperature and surrounding matrix are performed to understand and reduce non-radiative processes. Pump-probe studies address the Auger recombination kinetics. Time-resolved spectroscopy allows measuring the coupling to phonons and the homogeneous linewidths. This project defines the physical boundaries for the possible properties of these n-doped colloidal quantum dots, and therefore informs the degree to which these new infrared chromophores could transform infrared technologies.