Liquid hydridosilane precursor prepared from cyclopentasilane via sonication at low temperatures without the action of light

Abstract

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.

From Cyclopentasilane to Thin‐Film Transistors

“…[ 3 ] The applied solutions of polyhydrosilanes or Si nanoparticles are used to deposit thin films of amorphous silicon (a:Si). In general, the required processing involves a solution of or a neat molecular hydrosilane which is treated with heat, [ 4 ] ultrasound, [ 5 ] or UV light [ 6 ] to form a liquid oligomerized hydrosilane, also known as “liquid Si” or “Si ink.” From these liquids, thin films can be formed via different deposition techniques such as spin coating, dip coating, ink jet, or other printing and spraying methods. After a heat treatment step at comparatively low temperatures between 300 and 500 °C, very pure a:Si films are obtained for processing into electronic devices.…”

“…With respect to film formation, the formulation of the silane ink, the deposition, and drying of the film have to be orchestrated to yield the desired behavior (steps I to IV). Toluene, [ 19 ] cyclohexane, [ 5 ] and cyclooctane [ 5,7 ] or respective mixtures [ 9 ] have proven to dissolve both pure and polymerized CPS and deliver good wettability on typical substrates. The formulation of prepolymerized dihydrosilanes benefits from an addition of pure CPS.…”

“…The formulation of prepolymerized dihydrosilanes benefits from an addition of pure CPS. [ 2 ] Deposition of silane inks has been demonstrated by spin coating [ 5,7,9 ] spray coating [ 20 ] slot‐die coating, [ 9 ] and ink‐jet printing [ 2,21 ] (step II). Layers as thick as 300 nm were realized by doctor blading of pure CPS.…”

Fabrication of n-type Si nanostructures by direct nanoimprinting with liquid-Si ink

“…However, by using liquid hydrosilanes (Si x H y ) such as cyclopentasilane (Si 5 H 10 ), 1 cyclohexasilane (Si 6 H 12 ), and neopentasilane (Si 5 H 12 ) and their respective polymers, Si thin films can be fabricated without costly vacuum equipment. [2][3][4][5][6][7][8][9] Fabricating Si films from liquid materials allows high-throughput production of large-area films using traditional coating methods such as spin-coating, slot-die coating, and inkjet printing; the equipment required for these methods is relatively inexpensive and simple. In addition, nanostructures can be fabricated directly onto a substrate through imprinting in which a mold is pressed into a thin coat of the liquid ink and the nanostructures are cured by heat or light exposure.…”

Approaching Solar‐Grade a‐Si:H for Photovoltaic Applications via Atmospheric Pressure CVD Using a Trisilane‐Derived Liquid Precursor

“…Intrinsic and doped inks have previously been synthesized from a variety of different monomers, these include the cyclic silanes cyclopentasilane (CPS, Si 5 H 10 ) and cyclohexasilane (CHS, Si 6 H 12 ), and the branched molecule neopentasilane (NPS, Si 5 H 12 ) . Solution‐processed a‐Si:H layers have been deposition via inkjet printing, spin coating, slot die coating, atmospheric pressure chemical vapor deposition (APCVD), and aerosol‐assisted APCVD (AA‐APCVD) .…”