Improving the performance of inverted organic solar cells by embedding silica‐coated silver nanoparticles deposited by electron‐beam evaporation

Embedding metallic nanoparticles (MNPs) in organic solar cells (OSCs) is proposed as one of the promising strategies to enhance their photovoltaic performance owing to localized surface plasmon resonance, light scattering effects or a synergy of both effects derived from the MNPs. However, it has been demonstrated that MNPs wrapped by a thin dielectric silica shell can lead to better photovoltaic yield than bare MNPs due to the presence of the dielectric shell which avoids direct contact between the active layer and the MNPs, reducing the charge recombination and the exciton quenching loss at the metal surface. In this study, we report an alternative solution using an ultrathin dielectric layer coating silver nanoparticles (Ag NPs) for improving the performance of plasmonic inverted OSCs instead of the use of metal–dielectric core–shell NPs. A silica (SiO₂) layer 5 nm thick coating evaporated Ag NPs with an average size of 60 nm is deposited on top of the zinc oxide (ZnO) layer used as the electron transport layer, leading to a significant improvement in the short‐circuit current density (J_sc) and the power conversion efficiency (PCE) of the inverted OSCs. The electron‐beam evaporation method is employed for controlled deposition of Ag NPs and SiO₂ on the ZnO layer. The plasmonic devices resulted in an 18% and 14.1% enhancement of the J_sc and PCE, respectively, compared to reference devices. This increase of the photoelectric parameters in plasmonic devices is attributed not only to the plasmonic effects originating from the Ag NPs but also to the ultrathin silica layer which can contribute to facilitating charge extraction. © 2019 Society of Chemical Industry