Vapor Induced Donor–Acceptor Interface to Enhance The Performance of Bilayer Organic Solar Cells

In this study, we introduce the vapor‐induced donor–acceptor interface (VIDAI) method to enhance the performance of bilayer organic solar cells (OSCs) through direct solvent vapor treatment at the donor–acceptor interface. Using the inverted device structure ITO/ZnO/D18/Y6/MoO 3 /Ag, we applied 1‐chloronaphthalene (CN) and 1,8‐diiodooctane (DIO) vapors directly to the donor layer to treat the interface between the D18 and Y6 layers. Compared to the nontreated devices, the devices incorporating VIDAI demonstrated improvements in power conversion efficiency (PCE) under 1 sun illumination from 15.1% to 16.8% and 17.0% for CN and DIO, respectively, and for indoor illumination from 13.2% to 14.9% and 15.0% for CN and DIO, respectively. This is attributed to optimized surface tension and improved recombination lifetime. Additionally, the VIDAI method enhanced device stability, with the DIO‐treated device exhibiting the highest maximum power point stability. This work establishes VIDAI as a simple, and effective, strategy for optimizing the efficiency and stability of bilayer OSCs, paving the way for their application in both outdoor and indoor energy harvesting.