A.P. Cádiz Bedini, C. Chen, B. Klingebiel, P.H.L. Notten, U. Rau
Keywords: silicon, hydrogen, nanoparticles, ultrasound, silanes, lithium-ion, battery, solar cells, solution-processing
Summary:Silicon nanoparticles (Si-NPs) have become increasingly relevant in several important fields ranging from solar cells, next-generation quantum dot LEDs, lithium-ion batteries, and because silicon is biodegradable, their use as drug carriers or fluorescent markers has also begun to be explored. Here we report on a scalable and surprisingly simple ambient temperature and pressure method for the synthesis of Si-NPs using semiconductor-grade purity trisilane (Si3H8) and ultrasound. The method relies on the chemical effects associated with acoustic cavitation and, in particular, on the generation of localized hot spots upon bubble collapse. We argue that this is a break-through in nanosilicon synthesis and a trigger for innovation in several distinct fields (1). We demonstrate via various spectroscopic techniques (FTIR, Raman, XPS, EELS) and electron microscopy images (SEM, (S)TEM) that simple variation of the preparation conditions leads to the synthesis of discrete, unoxidized, hydrogenated, and amorphous Si-NPs of tunable size in the range of 1.5 to 30 nm. Moreover, we show that under certain conditions, sustained ultrasonic irradiation yields highly porous, sponge-like Si-NP agglomerates with nanoscopic high specific surface area morphologies. For both particles and agglomerates, the hydrogen concentration can be modified by post-synthesis annealing. The as-produced Si-NPs agglomerates are implemented as high performance anode materials for lithium-ion batteries and their electrochemical performance is investigated by cyclic voltammetry and galvanostatic (dis)charging. We show, amongst other things, that the Si-NP anodes are stable even without any binders or conductive additives. Lastly, we present further applications such as silicon hydride polymer/Si-NP composite inks for making hydrogenated amorphous silicon (a-Si:H) thin films (2) and solar cells (3). We also show that our synthesis technique opens the door to a new sonochemistry of silanes (4) allowing for the preparation of silicon composite materials and may also enable a radically different way of implosively encapsulating therapeutic agents. 1. A. P. Cádiz Bedini, B. Klingebiel, M. Luysberg, R. Carius, Sonochemical synthesis of hydrogenated amorphous silicon nanoparticles from liquid trisilane at ambient temperature and pressure. Ultrason. Sonochem. 39, 883–888 (2017). 2. A. P. Cádiz Bedini et al., Sonophotolytically Synthesized Silicon Nanoparticle-Polymer Composite Ink from a Commercially Available Lower Silane. Macromol. Chem. Phys. 217, 1655–1660 (2016). 3. A. P. Cádiz Bedini, L. D. Trieu, S. Muthmann, U. Rau, R. Carius, Approaching Solar-Grade a-Si:H for Photovoltaic Applications via Atmospheric Pressure CVD Using a Trisilane-Derived Liquid Precursor. Sol. RRL. 1, 1700030 (2017). 4. A. P. Cádiz Bedini et al., Liquid hydridosilane precursor prepared from cyclopentasilane via sonication at low temperatures without the action of light. Ultrason. Sonochem. 34, 289–293 (2017).