In optoelectronic devices such as solar cells and photodetectors, a portion of electron-hole pairs is generated as so-called hot carriers with an excess kinetic energy that is typically lost as heat. The long-standing aim to harvest this excess energy to enhance device performance has proven to be very challenging, largely due to the extremely short-lived nature of hot carriers. Efforts thus focus on increasing the hot carrier relaxation time and on tailoring heterostructures that allow for hot-carrier extraction on short time and length scales. Recently, semiconductor nanowires have emerged as a promising system to achieve these aims, because they offer unique opportunities for heterostructure engineering as well as for potentially modified phononic properties that can lead to increased relaxation times. In this review we assess the current state of theory and experiments relating to hot-carrier dynamics in nanowires, with a focus on hot-carrier photovoltaics. To provide a foundation, we begin with a brief overview of the fundamental processes involved in hot-carrier relaxation and how these can be tailored and characterized in nanowires. We then analyze the advantages offered by nanowires as a system for hot-carrier devices and review the status of proof-of-principle experiments related to hot-carrier photovoltaics. To help interpret existing experiments on photocurrent extraction in nanowires we provide modeling based on non-equilibrium Green's functions. Finally, we identify open research questions that need to be answered in order to fully evaluate the potential nanowires offer toward achieving more efficient, hot-carrier based, optoelectronic devices.

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基于半导体纳米线的热载流子光电器件

在诸如太阳能电池和光电探测器之类的光电器件中，一部分电子-空穴对作为所谓的热载流子产生，其动能通常以热量的形式损失。长期的目标是收集这种多余的能量以提高设备性能，这已被证明是非常具有挑战性的，这主要是由于热载流子的寿命极短。因此，努力集中在增加热载流子弛豫时间和定制异质结构上，以允许在短时间内和长度尺度上提取热载流子。最近，半导体纳米线已成为实现这些目标的有前途的系统，因为它们为异质结构工程以及可能导致弛豫时间增加的潜在改进声子特性提供了独特的机会。在这篇综述中，我们评估了与纳米线中热载流子动力学相关的理论和实验的当前状态，重点是热载流子光伏。为了提供基础，我们首先简要概述热载流子弛豫涉及的基本过程，以及如何在纳米线中定制和表征这些过程。然后，我们分析了纳米线作为热载流子器件系统所提供的优势，并回顾了与热载流子光伏相关的原理验证实验的状态。为了帮助解释纳米线中光电流提取的现有实验，我们提供了基于非平衡格林函数的建模。最后，我们确定了需要回答的开放性研究问题，以便全面评估纳米线为实现更高效、基于热载流子、