Inverted Bulk‐Heterojunction Solar Cells using Polyethylenimine‐Ethoxylated Processed from a Fully Aqueous Dispersion as Electron‐Transport Layer

In this work, we present the realization and characterization of bulk-heterojunction (BHJ) solar cells in which we use a spin-coated polyethylenimine-ethoxylated (PEIE) layer as electron-transporting layer deposited from a fully water-based solution. We investigated several concentrations of PEIE in aqueous solution and characterized the chemical and electrical behavior of PEIE-coated fluorinated tin oxide (FTO) substrates. We realized BHJ solar cells using P3HT:PC60BM as active layer achieving a maximum efficiency of 4% that outperform the device fabricated using a 2-methoxyethanol-based PEIE solution considered as reference. Moreover, devices fabricated with the water-based PEIE solution showed a higher shelf-life stability compared to those made with the 2-methoxyethanol-based PEIE solution. The performances of the devices realized with the water-based solution were characterized over a period of more than 6 months showing a decrease of 30% in efficiency.