DUAL-FUNCTION SEMICONDUCTING POLYMER DEVICES - LIGHT-EMITTING AND PHOTODETECTING DIODES

Thin film devices made with poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene], MEH-PPV, are known to be efficient light-emitting diodes. The same devices, under reverse bias, exhibit excellent sensitivity as photodiodes. Thus the polymer tunnel diode is a dual-function device. For the Ca/MEH-PPV/ITO (indium/tin oxide) layered structure, the external quantum efficiency for electroluminescence is almost-equal-to 1% photons/electron (forward bias >2.5 V). The same device is sensitive as a photodiode: The dc sensitivity (-10 V, reverse bias) is 9X10(-2) A/W (at approximately 1-muW/cm2 input) corresponding to a quantum yield of more than 20% electrons/photon.