Indium–tin–oxide surface treatments: Influence on the performance of CuPc/C60 solar cells

In this work, we investigate the influence of different indium tin oxide (ITO) surface treatments on the performance of organic solar cells. ITO substrates have been characterized by Hall measurements, Seebeck coefficient measurements, surface sheet resistance measurements, and surface probe microscopy. Single layer (ITO/copper phthalocyanine (CuPc)/Al) and double layer (ITO/CuPc/C60/Al) solar cells were fabricated. It was found that the surface treatments changed the parameters of the ITO (work function, carrier concentration, sheet resistance, surface roughness) and significantly influenced the solar cell performance. The AM1 power conversion efficiency of the ITO/CuPc/C60/Al cell with optimal surface treatment (∼0.1%) is 1 order of magnitude larger than the power conversion efficiency of the solar cell fabricated on untreated ITO substrate (∼0.01%). The AM1 power conversion efficiency can be further enhanced with improved device structures. Obtained AM1 power conversion efficiency for a three layer structure ITO/CuPc/CuPc:C60 (1:1)/C60/Al was measured to be 0.16%.