A series of methylene-biphenylene-bridged silsesquioxane thin films were synthesized from 4,4′-bis(trimethoxysilylmethyl)biphenyl (MBP) and methyltrimethoxysilane (MTMS) monomers at different molar ratios. A sol−gel process employing hydrolysis and condensation reactions was used to synthesize the precursors that were then spin-coated onto a silicon wafer. Optical properties of the thin films were investigated using spectroscopic ellipsometry (SE). Refractive index values increased from 1.40 for 0 mol % MBP to 1.60 for 100 mol % MBP. These are promising results for reliable encapsulants for a high-performance white light emitting diode (LED) given its high refractive index value and absence of epoxy moieties. The dielectric functions, consisting of real and imaginary parts closely related to refractive index and extinction coefficient, were also investigated. A new peak at 3.96 eV was observed for the 75 and 100 mol % MBPs in the imaginary dielectric functions, which was absent for the 25 and 50 mol % MBPs. The main origin for the new peak was thought to be the same as that for the peak at 4.67 eV, from the pseudo B 1u ← A 1 g transition of the six-membered ring constituting the biphenyl group. Herein, we suggest that the peak at 3.96 eV is generated from interactions between the biphenyl rings in the silsesquioxane materials, which can be explained by the local field correction and/or the planarization models.
No takes yet. Share an insight, caveat, or question.
Choi et al. (2010) studied this question.