Designing Efficient Si Quantum Dots and LEDs by Quantifying Ligand Effects
Designing Efficient Si Quantum Dots and LEDs by Quantifying Ligand Effects
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DOI：
10.1021/acsami.1c18779
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发表时间：
2021-12-30
影响因子：
9.5
通讯作者：
Saitow, Ken-ichi
中科院分区：
文献类型：
--
作者：
Ono, Taisei;Xu, Yuping;Saitow, Ken-ichi
胶体硅量子点（SiQD）对下一代光源的影响是有希望的。然而，决定SiQD效率的因素，例如光致发光（PL）波长、PL量子产率（PLQY）和基于配体类型、配体覆盖率、应力和悬挂键的SiQD LED性能，尚未被量化。表征这些变量将加速SiQD的设计和实现。本文中，通过热解氢倍半硅氧烷合成胶体SiQD，并且通过热氢化硅烷化（HT-SiQD）或使用PCl 5的室温氢化硅烷化（RT-SiQD）用1-癸烯终止其表面。结果，PL、PL激发和紫外-可见吸收光谱相似，但它们的PLQY显著不同：54%（RT-SiQD）vs 19%（HT-SiQD）。为了理解它们的相似性和差异，测定了表面覆盖率（悬挂键、Si-H（（数学）Si-H-1、=Si-H-2和-Si-H-3）、Si-O-Si、Si-C、Si-Cl）。芯应力分析确定，终止于SiQD键位点的单个配体将Si-Si键长拉伸0.3%。从两个定义明确的SiQD，PLQY和SiQD LED效率归因于四个因素：低覆盖率的绝缘体配体，Cl配体的辐射和非辐射率的影响，可忽略的悬挂键，和SiQD的核心与低拉伸应力。RT-SiQD在甲苯中的PLQY为80%。此外，LED的20倍电致发光强度差异源于电流密度的10倍差异和俄歇复合的2倍差异。这里展示的概念可以应用于进一步提高具有其他配体的SiQD的PLQY和LED效率。
The impact of colloidal silicon quantum dots (SiQDs) on next-generation light sources is promising. However, factors determining the efficiency of SiQDs, such as the photoluminescence (PL) wavelength, PL quantum yield (PLQY), and the SiQD LED performance based on the type of ligand, ligand coverage, stress, and dangling bonds, have not been quantified. Characterizing these variables would accelerate the design and implementation of SiQDs. Herein, colloidal SiQDs were synthesized by pyrolyzing hydrogen silsesquioxane and their surfaces were terminated with 1-decene by either thermal hydrosilylation (HT-SiQDs) or room-temperature hydrosilylation using PCl5 (RT-SiQD). As a result, PL, PL-excitation, and ultraviolet-visible absorption spectra were similar, but their PLQYs were significantly different: 54% (RT-SiQDs) vs 19% (HT-SiQDs). To understand their similarities and differences, surface coverages (dangling bonds, Si-H ((math)Si-H-1, =Si-H-2, and -Si-H-3), Si-O-Si, Si-C, Si-Cl) were determined. A core stress analysis established that a single ligand terminated to a SiQD bond site stretched the Si-Si bond length by 0.3%. From the two well-defined SiQDs, the PLQY and SiQD LED efficiency were attributed to four factors: low coverage of insulator ligands, the Cl ligand effect on radiative and nonradiative rates, negligible dangling bonds, and a SiQD core with low tensile stress. The PLQY of the RT-SiQDs in toluene was 80%. In addition, the 20x electroluminescence intensity difference of the LEDs originated from a 10x difference in current density and a 2x difference in Auger recombination. The concepts demonstrated here can be applied to further improve the PLQY and LED efficiencies of SiQDs with other ligands.