Polymer-polymer rectifying heterojunction based on poly(3,4-dicyanothiophene) and MEH-PPV

Thin, homogeneous films of a high electron affinity (n-dopable) polymer, po ly(3,4-dicyanothiophene) (PDCTh), were prepared by in-situ thermal polymeri zation of 2,5-diiodo-3,4-dicyanothiophene on substrates. As a result of the presence of two cyano substituents on the thiophene backbone, PDCTh is an electronegative polymer, with the LUMO at ca. 3.6 eV and the HOMO at ca. 6. 7 eV. We demonstrate the fabrication of polymer-polymer rectifying heteroju nctions using PDCTh and poly(2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) polymer layers on ITO-glass. Rectification ratios in th e current voltage characteristics of these devices exceed 10.(3) This devic e exhibits a photovoltaic effect with a de sensitivity at -3 V reverse bias of 4 x 10(-4) A/W or quantum yield of 0.1% electrons/photon. (C) 1998 John Wiley & Sons, Inc.