FORWARD REVERSE DC BIAS OR AC ELECTROLUMINESCENCE IN POLY(P-PHENYLENEVINYLENE) PREPARED VIA SULFONIUM-SALT AND XANTHATE ROUTES/

In light-emitting diodes (LEDs) of standard configuration - Indium-Tin -Oxide (ITO)/polymer/metal, we observed light emission under ac or for ward/reverse de bias, using poly(p-phenylene vinylenes) prepared via t he sulfonium salt (S-PPV) or xanthate (X-PPV) routes as active electro luminescent layers. S-PPV devices exhibited approximately symmetrical current-voltage characteristics under forward and reverse de bias with the same onset voltage. The electroluminescence (EL) spectra either u nder a de forward/reverse bias or ac were identical. X-PPV showed EL u nder reverse bias at higher voltage than in forward bias. Symmetrical current-voltage characteristics in S-PPV devices is attributed to ioni c impurities present in the polymer.