The present disclosure provides a display panel, its manufacturing method and a display device. The manufacturing method of the display panel comprises: forming, on a substrate, a thin film transistor comprising a gate electrode, an active layer, a source electrode and a drain electrode; forming a hydrogen diffusion barrier layer that covers the entire substrate, wherein the hydrogen diffusion barrier layer is electrically conductive and is electrically connected to the drain electrode; and forming a photosensitive structure layer on the hydrogen diffusion barrier layer.