Photovoltaic response of symmetric sandwich polymer cells with identical electrodes

Abstract

The photovoltaic response of symmetric sandwich polymer cells based on poly[5-(2′-ethylhexyloxy)-2-methoxy-1,4-phenylene vinylene] (MEH-PPV) and MEH-PPV:fullerene blends has been investigated. Identical, semitransparent gold, silver, aluminum, and calcium are used as top and bottom electrodes. Most of the nominally symmetric sandwich cells exhibit pronounced photovoltaic (PV) response. The PV parameters are strongly dependent on the direction of illumination, the active layer thickness, and the evaporation rate of top electrode. Open-circuit voltage as high as 0.7 V has been measured in silver/MEH-PPV/silver cells. The addition of fullerene leads to reduced open-circuit voltage and higher short-circuit current. The photovoltaic response observed in these nominally symmetric sandwich cells is attributed to their different top and bottom electrode interfaces.