We report on a liquid hydridosilane precursor ink prepared via the ultrasonically induced ring-opening polymerisation of cyclopentasilane (SiH) without irradiation by ultraviolet light. The sonication is carried out in N atmosphere at temperatures between 20 and 75°C. We use size exclusion chromatography (SEC) to show polymer growth and estimate molecular mass with increasing sonication time. In combination with UV-vis transmission measurements, further SEC analysis is used to compare solutions subjected to either purely thermal or ultrasonic treatment at the same process temperature and for the same duration. Our findings provide strong evidence showing that the initiation of the polymerisation is sonocatalytic in nature and not thermic due to the macroscopic temperature of the solution. The liquid precursor is used to produce homogeneous hydrogenated amorphous silicon (a-Si:H) thin films via spin coating and pyrolytic conversion. The optoelectronic properties of the films are subsequently improved by hydrogen radical treatment. Fourier transform infrared spectroscopy (FTIR) is used to determine a compact film morphology and electrical conductivity measurements show that the layers attain a light-to-dark photosensitivity ratio of 2×10 making them suitable for application in optoelectronic devices.
The preparation of a printable silicon ink using semiconductor grade and commercially available trisilane (Si3H8) is reported. The synthesis is carried out in solution at room temperature or below in N2 atmosphere at ambient pressure and involves an initial sonication step, followed by irradiation with ultraviolet light. The production of higher order silanes via ultrasound is demonstrated using gas chromatography and nuclear magnetic resonance measurements are used to show that a combined sonophotolytic treatment yields a highly branched silicon hydride polymer. In addition, scanning electron microscopy (SEM) images are used to ascertain the sonocatalytic production of silicon nanoparticles. Furthermore, it is argued that these particles are partially responsible for enabling dramatically accelerated polymer growth, not otherwise observed in the same amount of time using ultraviolet light alone. Finally, the utility of the ink used in this study is demonstrated for the field of printable electronics by fabricating amorphous silicon thin films by spin‐coating and atmospheric pressure chemical vapor deposition with optoelectronic properties approaching those of state‐of‐the‐art plasma enhanced chemical vapor deposition (PECVD) material.
The article demonstrates the fabrication of a-Si:H thin films in a N 2 -filled glove box via atmospheric pressure chemical vapor deposition (APCVD) using a vaporized silicon hydride polymer/silicon nanoparticle composite ink prepared from trisilane (Si 3 H 8 ). It is shown via Raman spectroscopy that the films exhibit good short and mid-range atomic order. Fourier transform infrared spectroscopy reveals a fairly compact microstructure and a hydrogen concentration of 13-18 at.%. Photothermal deflection spectroscopy demonstrates a sub band gap absorption only a factor of $6 higher than that of solar-grade plasma-enhanced CVD (PECVD) material. As a demonstration of the utility of our ink, c-Si wafer surface passivation layers are deposited resulting in effective minority charge carrier lifetimes exceeding 400 ms. These lifetimes constitute the as of yet highest reported values achieved using liquid precursors for bifacial coating without subsequent hydrogen radical treatment. The high electronic quality of the layers is shown via the fabrication of a n-i-p thin-film solar cell with an APCVD intrinsic absorber layer exhibiting an efficiency of 3.4% and hence, placing its photovoltaic performance among the highest reported for cells processed from the liquid phase and without a back reflector.
Silicon nanoparticles (Si-NPs) are increasing in relevance in diverse fields of scientific and nanotechnological inquiry, where currently some of the most important areas of research involve energy storage and biomedical applications. The present article is concerned with a curious and scalable method for the preparation of discrete, unoxidized, hydrogenated, and amorphous Si-NPs of tunable size in the range of 1.5-50nm. Using ultrasound generated with a conventional ultrasonic horn, the "fusion" of Si-NPs is demonstrated at ambient temperature and pressure by sonicating solutions containing readily available, semiconductor-grade purity trisilane (SiH). The only requirement for the synthesis is that it be carried out in an inert atmosphere such as that of a N-filled glove box. Various spectroscopic techniques and electron microscopy images are used to show that the size of the Si-NPs can be controlled by varying the amplitude of the ultrasonic waves or the concentration of trisilane in the solution. Moreover, sustained ultrasonic irradiation is found to yield highly porous Si-NP agglomerates that may find use in applications requiring non-crystalline nanoscopic high specific surface area morphologies.
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