Abstract
Low stability and degradability of polymers by ambient air, UV irradiation or charge transport are major problems of molecular electronics devices. Recent research tentatively suggests that the presence of a crystalline phase may increase polymer stability due to an intensive energy trapping in the ordered phase. Using the UV degradability, we demonstrate this effect on an archetypal model σ bonded polymer - poly[methyl(phenyl)silane] (PMPSi) - with partially crystalline and amorphous-like layers. UV degradation with 345 nm, derived from the branching state generation rate, was inversely proportional to the crystalline phase content, changing from 4.8x1011 s-1 (partially crystalline phase) to 1.8x1013 s-1 (amorphous-like phase). A model is proposed where crystallites formed by molecular packing act as effective excitation energy traps with a suppressed nonradiative recombination improving thus PMPSi film stability. The molecular packing and higher crystalline phase proportion may be a general approach for stability and degradability improvement of polymers in molecular electronics.
Highlights
The main chains in polysilanes are composed of single Si-Si σ bonds
Little attention has been paid to the short-scale mobility inside the elementary units, conformational composition and conformational ordering or disordering of these units.[3,4]
The Wide-Angle X-ray Scattering (WAXS) suggests existence of a long-range ordering in Poly(methyl-n-propylsilane) (PMPrS).[17]
Summary
The main chains in polysilanes are composed of single Si-Si σ bonds. The delocalization of sigma-orbitals along the silicon backbone results in a band gap between HOMO and LUMO as low as 3 eV which leads to a strong absorption and emission in the near-UV range with potential applications in photoconductors, semiconductors, nonlinear optical materials, LEDs and photoresists. We have introduced the Energy-Resolved Electrochemical Impedance Spectroscopy (ER-EIS) of DOS probing simultaneously HOMO, LUMO and deep defect states with a sensitivity in the order of 1014 cm-3eV-1.27,28 The ER-EIS method was used for elucidation of the quantum efficiency of the deep branching state formation in PMPSi after UV degradation.[29,30] The PMPSi is archetypal polymer ideally suited for such a study because its electronic properties strongly depend on the backbone conformation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
