Poly [[2-methoxy-5-(3-sulfonatopropoxy)-1, 4-phenylenel-1,2-ethenediyl] (MPS-PPV) was an anionic water-soluble conjugated polymer. A novel single-component light-emitting electrochemical cell (LEC) with an indiurn tin oxide/MPS-PPV/aluminum sandwich structure has been successfully fabricated. MPS-PPV serves as both luminescent material and ionic conductor in the active layer. Electroluminescence can be observed under both forward and reverse bias with emission maxima at about 520 nm (green light). In particular, the device has a low turn-on voltage of about +3V and -4V, and can sustain long-term operations without much loss of efficiency at ambient conditions. (c) 2006 Wiley Periodicals, Inc.