Photoluminescence and absorption spectra of poly(pentylphenylsilylene). Absence of broad photoluminescence of poly(alkylarylsilylene) around 2.7 eV

Absorption, photoluminescence (PL) and PL excitation (PLE) spectra of a solution and a thin film of poly(pentylphenylsilylene) (1) are measured and compared to those of poly(methylphenylsilylene) (2). The sharper and stronger 3.6 eV absorption and the mirror image of the absorption and PL spectra of 1 suggest that 1 is spatially homogeneous. The broad PL which appears in 2 is scarcely observable in the 1 film around 2.7 eV, in the range from room temperature to 20 K. A comparison of the PLE spectra shows that the origins of the broad PL of 1 and 2 are different. To obtain poly(alkylarylsilylene) derivatives with high molecular weights which show no visible PL, the alkyl pendants should be pentyl or longer.