Improvement of organic solar cell performance via the incorporation of a MgO cathode interlayer fabricated by a reaction of thermally deposited Mg with MoO3

Abstract

The use of magnesium oxide (MgO), which was formed by a reaction of thermally deposited magnesium with molybdenum trioxide, as a cathode interlayer material in vacuum-processed, planar pn-heterojunction organic solar cells (OSCs) using copper phthalocyanine and C70 and bulk-heterojunction (BHJ) OSCs using tris[(5-phenylthiophen-2-yl)phenyl]amine and C70 reduced the series resistance, thus improving the fill factor and power conversion efficiency (PCE). On the other hand, the use of the MgO cathode interlayer in solution-processed BHJ OSCs using poly(3-hexylthiophene) and [6,6]-phenyl-C71-butyric acid methyl ester improved the open-circuit voltage, thus improving the PCE. It is speculated that the improved performance is attributed to the high hole blocking ability of the MgO layer due to the deep-lying valence band level of MgO.