This disclosure provides a thin film transistor and the preparation method thereof, an array substrate, and a display panel, so as to solve the problem that the active layer is prone to be corroded when a metal oxide thin film transistor is produced by a back channel etching process. The preparation method comprises: forming a gate electrode metal thin film on a base substrate, and allowing the gate electrode metal thin film to form a gate electrode metal layer comprising a gate electrode by a patterning process; forming a gate electrode insulating layer on the gate electrode metal layer; forming an active layer on the gate electrode insulating layer; preparing a metal nanoparticle layer on the active layer, said metal nanoparticle layer being used as an etching protection layer; forming a source and drain electrode metal thin film on the base substrate on which the above processes are finished, and allowing the source and drain electrode metal thin film to form a source and drain electrode metal layer comprising a source electrode and a drain electrode by a patterning process, wherein the source electrode and the drain electrode cover a part of the metal nanoparticle layer; removing or oxidizing the part of the metal nanoparticle layer which is not covered by the source electrode and the drain electrode in an oxygen-containing atmosphere; and forming a passivation layer on the source and drain electrode metal layer.

A method for the preparation of a cohesive non-porous perovskite layer on a substrate (104) comprising: forming a thin film of a solution containing a perovskite material dissolved in a solvent onto the substrate to form a liquid film (104) of the solution on the substrate, applying a crystallisation agent (112) to a surface of the film to precipitate perovskite crystals from the 5 solution to form the cohesive non-porous perovskite layer (116) on the substrate.

The present method of forming a metal oxide film can increase production efficiency while maintaining the low resistance of the metal oxide film. The present method of forming a metal oxide film includes first misting a solution containing a metallic element and ethylenediamine; meanwhile, heating a substrate; and then, supplying the misted solution onto a first main surface of the substrate.