A Novel Ultra‐Thin and Smooth Sm:Ag Composite Electrode with High Visible Transmittance Enables Efficient Color‐Neutral Semitransparent Organic Solar Cells

Abstract Transparent top electrodes are crucial for enhancing the performance of semitransparent organic solar cells (ST‐OSCs). The commonly evaporated ultra‐thin silver (Ag) electrode in ST‐OSCs suffers from limited transparency and conductivity due to its island‐like growth, posing a challenge in achieving desired conductivity and low optical loss. Here, a novel composite film is prepared by doping a small amount of samarium (Sm) into Ag during evaporation. The incorporation of Sm facilitates to form a continuous ultra‐thin Ag film by suppressing isolated island growth. A 15 nm Sm:Ag composite film with an optimized mass ratio of 1:30 exhibits a sheet resistance of 6 Ω □ −1 and an average visible transmittance (AVT) of 66%, much better than 20 Ω □ −1 and 43% of the pure Ag analogue. By employing the Sm:Ag electrode with an optical coupling layer, the ST‐OSCs demonstrate a power conversion efficiency of 10.89% and an AVT of 37.1%, resulting in a light utilization efficiency of 4.04%. Moreover, the resultant ST‐OSCs demonstrate superior color neutrality with a color rendering index of 91.9, representing one of the highest values among the ST‐OSCs with LUE exceeding 4% reported to date. This work provides a novel transparent top electrode with superior conductivity and transmittance for ST‐OSCs.