Photoconductivity of poly(methylphenyl silylene) doped with dinitrobenzenes

Abstract

Abstract Poly(methylphenyl silylene) PMPSi was doped with the following compounds of the electron acceptor type: p-dinitrobenzene (pDNB), m-dinitrobenzene (mDNB), and o-dinitrobenzene (oDNB), up to concentrations of 3mol%. The quantum yield of charge carrier generation φ(cc) is significantly increased, relative to that of neat PMPSi, by pDNB (about four times at a field F = 2 × 107 V m−1 and 3mol%. mDNB and oDNB exert only a small effect on φ(cc). The extent of increase in φ(cc) is correlated with the electron affinity EA; both of them increase in the order oDNB < mDNB < pDNB. On the other hand, the hole drift mobility μ is influenced by the dipole moment p of the dopants. μ is increased by pDNB (p≈0 D) and decreased by mDNB (p≈3.8D) and oDNB (p≈6.0D). It is concluded that additives with p>0 interact (probably electrostatically) with holes passing through the polymer matrix. This results in an increase in the activation energy of μ or, in terms of the hopping transport model, in a broadening of the distribution of energy states of transporting sites or even in a change in the character of the distribution function. Requirements for dopants of the electron acceptor type regarding optimum improvement of the photoconductive properties of PMPSi are: low p values (close to zero) and high EA values.