Crystalline silicon is the most widely used semiconductor material today, with a market share of above 90%. Due
to its indirect electronic band structure, however, the material is not able to emit light effectively and therefore
cannot be used for key applications like light emitting diodes or lasers. Selected one or two-dimensional silicon
compounds like linear or branched polyilsilylenes or layered structures like siloxene, however, possess a direct
band gap and therefore exhibit intense visible photoluminescence. Siloxene, a solid state polymer with a sheet like
layered structure and an empirical formula Si6H6-n(OH)n, in particular, is considered as an alternative material for
Si-based luminescent devices. Detailed studies of structural and photophysical properties of the material, however,
are strongly impeded by its insolubility in organic solvents.
In a preceding study we were able to show, that polysiloxane polymers with two dimensional siloxene-like
structures containing cyclosilanyl subunits but also molecular cyclohexasilanes bearing siloxy-groups attached to
the polysilane ring are strongly photoluminescent. Novel, luminescent materials, therefore, might be accessible on
the basis of cyclohexasilanyl rings and oxygen containing side groups.
Thus, further investigations certainly will be helpful in order to generalize and to understand the outstanding
luminescence behavior of siloxycyclopolysilanes. In the current project, therefore, we'd like to propose
supplementary studies directed towards the dependence of siloxycyclopolysilane photoluminescence on substitution
pattern and ring size and towards the photoluminescence of soluble well defined polysiloxane oligomers with sheet
like or ladder type structures.
In the first part of the project appropriate currently mostly unknown model substances shall be synthesized,
structurally characterized and transformed to soluble polysiloxane oligomers with sheet like or ladder-type
structures containing cyclopolysilanyl subunits. In the second part of the project the solution and solid state
absorption and photoluminescence properties of the materials, thus obtained, shall be investigated in detail
including quantum yields and excited states life time measurements and computational studies.