The Effect of Metal in MoOx/Metal/MoOx Anode on Open Circuit Voltage in Organic Photovoltaic Cells

Abstract

Archetypal photovoltaic cells are fabricated in order to elucidate the effect of a metal embedded in a semitransparent trilayer electrode on photovoltage. A series of electrodes are formed by thermal deposition of MoOx, metal and MoOx layers, in said succession (MoOx = substoichometric molybdenum trioxide, metal = Au, Cu, Ag, Al, In, Mg, Yb). The parameters of the Schottky‐type cells consisting of thus made bottom anode, a subphthalocyanine boron chloride (SubPc) photoabsorber and a bilayer LiF/Al top cathode are measured and compared to those of the reference cell with an ITO/MoOx anode. Photovoltage does not correlate with the work function of a metal in the anode, while the photocurrent is inversely proportional to the anode sheet resistance. The highest efficiency is achieved with the silver interlayer, but the reference cell with ITO outperforms any cell with a trilayer anode. Then, comparison is made with a series of cells, in which the metal (Cr, Ni, Ag, Al, and Ta) in anode is deposited by a dc magnetron sputtering. In these cells, the photovoltage rises monotonically with the metal work function. Magnetron sputtered nickel in the anode provides the best cell performance, closely approaching that of the reference cell.