Air-Stable Inverted Organic Solar Cells with an Ultrathin Electron-Transport Layer Made by Atomic Layer Deposition

We report on the photovoltaic properties of air-stable inverted organic solar cells in which zinc oxide (ZnO) of varying thicknesses is formed as the electron-transport layer by an atomic layer deposition (ALD) method. The device performance was found to be dependent on the ZnO thickness. Air-stable inverted solar cells with an optimized ZnO thickness reached a power conversion efficiency of 2.91%. This efficiency was found to be comparable to those of conventional organic solar cells. The use of the ZnO electron-transport layer led to improved air stability: the power conversion efficiencies of unencapsulated organic solar cells remained above 80% of their original values even after storage in air for thirty days.