α-ZnO Manipulated Growth of Ag Gird on AgNWs Enables High Conductive Flexible Electrode for Large-Area Monolithic Organic Photovoltaics

The conductivity of AgNWs electrodes can be enhanced by incorporating Ag grids, thereby facilitating the development of large-area flexible organic solar cells (FOSCs). Ag grids from vacuum evaporation offer the advantages of simple film formation, adjustable thickness, and unique structure. However, the complex 3D multi-component structure of AgNWs electrodes will exacerbate the aggregation of large Ag particles, causing the device short circuits. To address this issue, the relationship between the surface energy of modification layers and the morphology and conductivity of ultrathin Ag on AgNWs is studied. The amorphous ZnO (α-ZnO) layer promotes Ag growth from Volmer-Weber (VW) to Frank-Van der Merwe (FM), reducing particle aggregation. The 1 µm thick PET/AgNWs/Ag grid electrode with α-ZnO exhibited low contact resistance and high conductivity. As a result, 1 cm² FOSCs with Ag grids achieve a power conversion efficiency (PCE) of 16.01%. As the area increased to 4 and 9 cm², the performance of the monolithic FOSCs is 14.70% and 12.69%, showing less efficiency loss during upscaling. The 8 and 16 cm² modules constructed by series and parallel connection of the monolithic devices yield PCEs of 14.47% and 12.92%, respectively. This study offers valuable insights into constructing Ag grids on AgNWs electrodes for highly efficient large-area FOSCs.