Investigating the Competition Between Exciton Delocalization and Radiative Recombination in 1D Semiconductor Quantum Wires

非技术描述：长度超过微米的一维半导体导线可以有效地吸收光，进而在半导体中产生移动载流子。当这些材料的直径变小时，从纳米到几十纳米的数量级，优先被吸收的光的颜色和半导体材料内载流子的能量都可以被操纵。这些一维材料被称为半导体纳米线，它们代表了能够有效地产生电荷并沿特定方向传输电荷的最小结构。这一跨学科研究项目的主要目标是从电荷载流子的产生和传输的角度来表征半导体纳米线的效率。重点是优化半导体纳米线的化学和物理性质，以便评估其在应用设计中的可行性。这项研究同时使用了传统的光学光谱学和先进的激光技术来探测纳米线内载流子的能量，并表征这些载流子的命运随时间和沿单根纳米线的位置的函数。特别注意测量载流子沿纳米线长度的传输情况。该项目的另一个重点是培训下一代科学家，特别是那些来自代表性不足的背景、具有不同材料科学、化学和物理专业知识的科学家。技术说明：本研究致力于优化溶液-液-固三相法合成的半导体量子线的性能，特别是对碲化镉和硒化镉量子线进行优化。研究小组正在进行吸光度和光致发光光谱实验，以表征它们内部光生载流子的能量，以及这些纳米结构的光致发光量子产率。通过光致发光寿命和瞬时吸收光谱实验表征了量子线中电子、空穴和激子的动力学。具体目标包括：1)表征激子寿命与光致发光量子产率、表面钝化和量子线结构质量的关系；2)测量激子沿单根量子线的扩散长度及其与光致发光量子产率、表面钝化和量子线结构质量的关系；以及3)研究有效激子扩散与量子线内辐射复合几率之间的明显竞争。

Nontechnical Description: One-dimensional semiconductor wires with lengths longer than micrometers can efficiently absorb light that in turn generates mobile charge carriers within the semiconductor. When the diameters of these materials become small, on the order of nanometers to tens of nanometers, both the colors of the light that are preferentially absorbed and the energies of the charge carriers within the semiconductor material can be manipulated. These one-dimensional materials are called semiconductor nanowires, and they represent the smallest structures that can efficiently generate and transport charges along specific directions. The main goal of this interdisciplinary research project is to characterize the efficiency of semiconductor nanowires in terms of charge-carrier generation and transport. An emphasis is placed on optimizing the chemical and physical properties of semiconductor nanowires so their viability in application designs can be evaluated. The research uses both traditional optical spectroscopy and advanced laser techniques to probe the energies of the charge carriers within the nanowires and to characterize the fate of these charge carriers as a function of time and position along single nanowire. Particular attention is given to measuring how well the charge carriers are transported along the length of the nanowires. Another focus of this project is on training the next generation of scientists, especially those from underrepresented backgrounds with diverse expertise in materials science, chemistry, and physics. Technical Description: This research is focused on optimizing the properties of semiconductor quantum wires synthesized by using the solution-liquid-solid strategy with a particular focus on cadmium telluride and cadmium selenide quantum wires. The research team is performing absorbance and photoluminescence spectroscopy experiments to characterize the energies of charge carriers photo-generated within them as well as the photoluminescence quantum yields of the these nanostructures. The dynamics of the electrons, holes, and excitons within the quantum wires are characterized by performing photoluminescence lifetime and transient absorption spectroscopy experiments. Specific goals include: 1) characterization of the exciton lifetime dependences on photoluminescence quantum yield, surface passivation and structural quality of the quantum wires; 2) measurement of exciton diffusion length along single quantum wires and its dependence on photoluminescence quantum yield, surface passivation and quantum wire structural quality; and 3) investigation of the apparent competition between efficient exciton diffusion and the probability for radiative recombination within the quantum wires.