Polymer diodes using poly(3,4-dicyanothiophene)

We have succeeded in the in-situ polymerization of thin, highly homogeneous films of poly(3,4-dicyanothiophene), PDCTh, on conducting substrates by heating the precursor monomer, 2,5-diiodo-3,4-dicyanothiophene. As a result of the presence of two cyano substituents on the thiophene backbone, PDCTh is an electronegative polymer, with depressed HOMO (6.7 eV) and LUMO (3.6 eV) levels. We demonstrate a polymer diode using PDCTh and poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene), MEH-PPV. The device, which has the structure Au/PDCTh/MEH-PPV/Au, has rectification ratios in the current voltage characteristics in excess of 103 and is a photodiode with a dc sensitivity at -3 V reverse bias of 4×10−4 A/W or a quantum yield of 0.1% electrons/photon