**4. ITO-free OSCs based on Ag thin-film electrodes**

In this section, ITO‐free OSCs based on (MoO3/)Ag thin‐film electrodes on glass or PET substrates are fabricated, and the best performance of OSCs is obtained by optimizing the thicknesses of Ag film and MoO3 interlayer. And the underlying mechanism, especially the Ag thin‐film growth and film properties are also investigated.
