Impact of Ink Synthesis on Processing and Properties of Inkjet-Printed Silicon Thin Films
Abstract
Inkjet printing has a high potential for cost reduction in solar cell and thermoelectric industry. This study demonstrates that silicon thin films can be produced by inkjet-printing of a silicon ink followed by consequent drying and annealing steps. Ink formulation is a crucial parameter for sintering of the silicon nanoparticles and control of the microstructure at low temperature. Evolution of the sintering steps is monitored by scanning electron microscopy and by Raman spectroscopy which offers a fast and precise characterization of the microstructure and chemical composition of the thin films. While denser and more crystalline layers are obtained, cracks appear within thin film and substrate because of stress provoked by oxidation of the surface. Electrical conductivity is improved with higher annealing temperature until a threshold where both physical degradation and oxidation of the layers limits strongly the carrier transport phenomenon. In opposition transmission of the thin films is altered with increasing annealing temperature. Evolution of the thermal conductivity is performed by Raman spectroscopy and can be tailor in a large range between ~1 to ~100 W/mK. Therefore control of the microstructure evolution with applied annealing process allows tailoring of both microstructure and thermal conductivity of the thin films.