Solution-Processed Silicon Thin Films and Electron Devices from Polysilane Precursors

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The deposition of silicon thin films from dissolved and formulated polysilane precursors and the integration of the layers into electronic applications are the main goals of the proposed project.In comparison to other inorganic materials from liquid-phase deposition, silicon is supposed to offer advantages in terms of fundamental device parameters (e.g. carrier mobilities), stability and reliability, as wellas controllability of material parameters (e.g. doping).The scientific challenges of the proposed project are significant improvements in- reproducibility and yield of the synthesis of cyclosilane and polysilane precursor solutions for application in spin casting, spray casting or printing techniques,- the functionality of silane molecules. A novel approach of this proposal is the synthesis of multi-functional silane molecules delivering the capability of in situ doping or crystallization enhancement during layer transformation, as well as- the transformation of the deposited precursor films into amorphous, nano-, or polycrystalline silicon films meeting the requirements of printed electronics manufacturing. In detail we will investigate> thermal and photonic annealing for reduced energy dissipation into the substrate, making the processing suited for technical glasses or plastic substrates,> utilization of metal-induced crystallization techniques lowering the overall thermal budget of thin-film processing. Metal-induced crystallization is applied to pre-deposited amorphous films from polysilane precursors as well as directly integrated into the precursor transformation by incorporation of active species during molecule synthesis or ink formulation.The applicability of the amorphous and polysilicon thin films is demonstrated by preparation of selected unipolar and bipolar electron devices, namely thin-film transistors and solar cells. Consequently, the processing activities of the proposal aim at an optimization of the electronic properties of the silicon thin films with respect to the target devices, i.e. defect control, charge transport, as well as doping.Two institutes with outstanding expertise in the areas of silicon chemistry (TU BA Freiberg) and devices and process technology (FAU Erlangen) will closely cooperate on this project.