ELECTROLUMINESCENT CHARACTERISTICS OF ONE-DIMENSIONAL SILICON CHAINS IN DIALKYL POLYSILANES

We investigate the electroluminescent characteristics of polysilane-ba sed single-layer light-emitting diodes (LEDs) which employ poly(di-n-h exylsilane) (PDHS) or poly(di-n-butylsilane) (PDBS) (PDHS-LED and PDBS -LED, respectively). The PDHS-LED exhibits an electroluminescence (EL) identical to its photoluminescence (PL), which is composed of an emis sion only in the near-ultraviolet (NUV) region. By contrast, the PDBS- LED exhibits EL in both the visible and NW regions. Although these two polysilanes differ only in terms of their substituent groups, their d evice characteristics vary considerably: the PDBS-LED exhibits a large r device current, inferior rectifying behavior, and a lower turn-on vo ltage than the PDHS-LED. This observation is inconsistent with predict ions based on the hypothetical band diagrams of these two LEDs. We hav e demonstrated the fundamental EL characteristics of sigma-conjugated one-dimensional Si chains by using PDHS, which has a highly ordered ba ckbone conformation and negligible structural defects. (C) 1997 Elsevi er Science S.A.