Guided‐Growth Ultrathin Metal Film Enabled Efficient Semi‐Transparent Organic Solar Cells

Abstract Semi‐transparent organic solar cells (STOSCs) have great potential in power‐generating windows for building facades and automobiles. At present, the evaporated metal thin film is widely used as the transparent top electrode in STOSCs owing to its relatively high conductivity. However, its transmittance in the visible range is sacrificed for fulfilling the thickness requirement of the electrical percolation threshold. Herein, a facile approach of introducing pre‐located Ag nanoparticles (NPs) with an optimized amount of ligands is demonstrated to promote the high‐quality and ultrathin evaporated Ag film formation for high‐performance transparent electrodes beyond that of merely evaporated electrodes. With the pre‐located and ligand‐optimized Ag NPs, the growth of evaporated Ag clusters can be guided to form high‐quality transparent electrode. Equally important, the approach also reduces the mis‐stacking defects of the electron transport layer and thus favors the carrier transportation/extraction to the electrode. By using these Ag NPs/7 nm Ag with a sheet resistance less than 15 Ω sq⁻¹ and average transmittance of 59.30% in the visible region as the main structure in the top electrode, a PM6:L8‐BO based STOSC achieves light utilization efficiency of 4.422% with a remarkable power conversion efficiency of 12.80%. This work provides a facile strategy to not only realize high‐quality and transparent ultrathin electrode with detailed understanding, but also to promote the practical applications of semi‐transparent photonic devices.