UV created weak and dangling bonds in aryl-substituted polysilylenes

Abstract

The susceptibility of aryl-substituted polysilylanes to photodegradation by UV radiation is examined on the prototypical organosilicon polymers, poly[methyl(phenyl)silylene] (PMPSi) and poly[(biphenyl-4-yl)methylsilylene] (PBMSi). The main purpose of this work is to study photoluminescence (PL) after UV major degradation for two different degradation wavelengths 266 and 355nm, predominantly in long wave range 400–600nm, studying the disorder, dangling bonds (DB) and weak bonds (WB) created by the degradation process. We claim that the PL of the 500–600nm band is related to the existence of WB on Si chain. Increase of the normalized PL 520–540nm band after UV degradation can be then evaluated as the increase of the density of states (DOS) of WB. The efficiency of the WB creation in PMPSi is greater for 266nm irradiation, supporting the notion of the suppressed exciton transport compared to the less energetical photon of 355nm, where the WB creation is lowered due to the exciton migration to longer segments and/or already existing defects. For PBMSi the WB creation kinetics for 355nm degradation is similar to that of PMPSi. The 266nm degradation results then support the model calculations of DB and WB reconstruction in more rigid Si skeleton.