Low-indium content bilayer transparent conducting oxide thin films as effective anodes in organic photovoltaic cells

Bilayer In-doped CdO/Sn-doped In2O3 (CIO/ITO) transparent conducting oxide (TCO) thin films were prepared by depositing thin ITO films by ion-assisted deposition on CIO films grown by metal-organic chemical vapor deposition. The optical, electrical, and microstructural properties of these bilayer TCO films were investigated in detail. A low sheet resistance of ~ 4.9 Ω/□ is achieved for the CIO/ITO (170/40 nm) bilayers without annealing. With a significantly lower In content (20 vs. ~ 93 at.%) and a much higher conductivity (> 12,000 vs. 3000–5000 S/cm) than commercial ITO, these bilayer films were investigated as anodes in bulk-heterojunction organic photovoltaic (OPV) devices having a poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene) + [6,6]-phenyl C61 butyric acid methyl ester active layer. Device performance metrics in every way comparable to those of devices fabricated on commercial ITO are achieved, demonstrating that CIO/ITO bilayers are promising low-In content, highly conductive and transparent electrode candidates for OPV cells.