Prajapati K N, Johns Ben, Bandopadhyay K, Silva S Ravi P, Mitra J
School of Physics, Indian Institute of Science Education and Research, Thiruvananthapuram 695551, India.
Department of Functional Materials, Łukasiewicz Research Network-Institute of Electronic Materials Technology, Wolczynska 133, Warsaw, Poland.
J Chem Phys. 2020 Feb 14;152(6):064704. doi: 10.1063/1.5138944.
We model the enhancement of near band edge emission from ZnO nanorods using plasmonic metal nanoparticles and compare it with emission enhancement from ZnO with semiconducting quantum dots. Selected CdSe quantum dots with absorption energies close to those of Ag and Au nanoparticles are chosen to construct model systems with ZnO to comprehend the role of ZnO's intrinsic defects and plasmonic excitation in realizing the spectrally selective luminescence enhancement. Excitation wavelength dependent photoluminescence spectra along with theoretical models quantifying the related transitions and plasmonic absorption reveal that a complex mechanism of charge transfer between the ZnO nanorods and metal nanoparticles or quantum dots is essential along with an optimal energy band alignment for realizing emission enhancement. The theoretical model presented also provides a direct method of quantifying the relative transition rate constants associated with various electronic transitions in ZnO and their change upon the incorporation of plasmonic nanoparticles. The results indicate that, while the presence of deep level defect states may facilitate the essential charge transfer process between ZnO and the plasmonic nanoparticles, their presence alone does not guarantee UV emission enhancement and strong plasmonic coupling between the two systems. The results offer clues to designing novel multicomponent systems with coupled plasmonic and charge transfer effects for applications in charge localization, energy harvesting, and luminescence enhancement, especially in electrically triggered nanophotonic applications.
我们利用等离子体金属纳米颗粒对氧化锌纳米棒近带边发射的增强进行建模，并将其与氧化锌和半导体量子点的发射增强进行比较。选择吸收能量与银和金纳米颗粒相近的特定硒化镉量子点，与氧化锌构建模型系统，以理解氧化锌固有缺陷和等离子体激发在实现光谱选择性发光增强中的作用。与理论模型相结合的激发波长相关光致发光光谱，量化了相关跃迁和等离子体吸收，结果表明，氧化锌纳米棒与金属纳米颗粒或量子点之间复杂的电荷转移机制以及最佳的能带排列，对于实现发射增强至关重要。所提出的理论模型还提供了一种直接方法，用于量化氧化锌中各种电子跃迁相关的相对跃迁速率常数，以及掺入等离子体纳米颗粒后它们的变化。结果表明，虽然深能级缺陷态的存在可能有助于氧化锌与等离子体纳米颗粒之间的基本电荷转移过程，但仅其存在并不能保证紫外发射增强以及两个系统之间的强等离子体耦合。这些结果为设计具有耦合等离子体和电荷转移效应的新型多组分系统提供了线索，可用于电荷定位、能量收集和发光增强应用，特别是在电触发纳米光子学应用中。
