Visible photoluminescence from silicon-backbone polymers

We have studied optical properties of Si-backbone polymers constructed by the organosilicon units having two or three Si-Si bonds in order to understand the mechanism of visible luminescence in silicon-based materials. The backbones of branch, ladder, and network polymers are constructed by the organosilicon units with three Si-Si bonds, and these polymers exhibit broad photoluminescence spectra in the visible spectral region. Sharp luminescence spectra are observed in quasi-one-dimensional chain and quasi-two-dimensional planar siloxene structures. The luminescence properties in branch, ladder, and network polymers are entirely different from those of one-dimensional or two-dimensional excitons in Si-backbone structures. Broad visible luminescence spectra with large Stokes shifts originate from the radiative recombination of excitons localized in disordered Si-backbone structures with three Si-Si bonds.