Adsorbate Engineering on ZnO for Ultraviolet Light Activation‐Free Organic Photovoltaic Modules

Abstract

Ultraviolet (UV) light is typically needed to activate inverted organic photovoltaic (OPV) devices with zinc oxide (ZnO) as the electron transporting layer (ETL) for enhanced efficiency. Given that UV light may cause the degradation of active layers and interfaces, and considering the absence of UV light in typical indoor lighting, addressing the need of UV light activation for ZnO becomes paramount. Herein, the engineering of adsorbates on ZnO could solve this issue by increasing the annealing temperature and changing the recipe of ZnO. Increasing the content of O 1s at binding energy of 531 eV on ZnO in X‐ray photoelectron spectroscopy would be beneficial to alleviate the need of UV light activation. For the (ZnO)PEIE (zinc acetate dihydrate (ZAH) and polyethylenimine ethoxylated (PEIE) dissolved in 2‐methoxyethanol, PEIE used to provide amine in the precursor), annealing at 180 °C would eliminated S‐shape in the current density‐voltage (J–V) characteristics without UV light activation. OPV modules (9.8 cm2) with 180 °C‐annealed (ZnO)PEIE as ETL achieved an efficiency of 18.2% under indoor lighting and 14.8%  under 1 sun with the UV filter (light intensity of 0.788 sun). These high efficiencies are achieved in the modules without the need for UV light activation.