Development of Inverted Organic Solar Cells with TiO2 Interface Layer by Using Low-Temperature Atomic Layer Deposition

Organic solar cells (OSCs) with inverted structure have attracted much attention in recent years because of their improved device air stability due to the use of stable materials for electrodes and interface layers. In this work, TiO2 films, fabricated using low temperature (e.g., 130-170 degrees C) atomic layer deposition (ALD) on ITO substrates, are used as electron selective interface layers to investigate inverted OSCs. It is found that though the as-deposited TiO2 films are high resistive due to the presence of oxygen defects, the defects can be significantly reduced by light soaking. PV cells with 15-nm-thick amorphous-TiO2 layers fabricated at low temperature show better performance than those with poly crystal TiO2 with same thickness deposited at 250 degrees C. The low temperature ALD-grown TiO2 films are dense, stable and robust with capability of conformal coating on nanostructural surfaces, showing a promising interface layer for achieving air-stable plastic OSCs with roll-to-roll mass production potential.