NOVELTY - Patterning (m1) a mesoporous inorganic oxide film involves: forming a mesoporous inorganic oxide film using a neutral composition containing inorganic oxide particles; and forming a pattern on the mesoporous inorganic oxide film using an elastic stamp for pattern formation, and then calcining the mesoporous inorganic oxide film. The calcination process is carried out at 200-450 degrees C.    USE - For patterning a mesoporous inorganic oxide film which is used for producing a photoelectrode (claimed) that is used in the production of electronic devices including mesoporous inorganic oxide films, e.g. solar cells, field effect transistors, organic thin film transistors, and light emitting diodes.    ADVANTAGE - The present patterning method allows patterning of a mesoporous inorganic oxide film containing inorganic oxide particles in a simple and effective manner using a nanostamping method. The photoelectrode that has been patterned by using the present patterning method increases the photoelectric conversion efficiency of a solar cell through an effective light harvesting technology. The method for producing the photoelectrode is simple and low cost process, can be applied to mass production processes, and is useful for the production of large-sized solar cells.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) producing (p1) a photoelectrode involving: forming a mesoporous inorganic oxide layer on a conductive substrate using a composition containing neutral mesoporous inorganic oxide particles forming a pattern on the mesoporous inorganic oxide layer using an elastic stamp for pattern formation; adsorbing a dye to the mesoporous inorganic oxide layer on which the pattern is formed and injecting a hole transfer material into the mesoporous inorganic oxide layer in which the dye is adsorbed, where the injection of a hole transfer material involves a process of allowing a composition containing a monomer of an electroconductive polymer for forming a hole transfer material to penetrate into the patterned inorganic oxide layer, and then thermally polymerizing the monomer to form an electroconductive polymer for hole transfer material; and further involves forming an interface adhesive layer on a conductive substrate using a composition containing a precursor of the inorganic oxide, before the process of forming a mesoporous inorganic oxide layer, and injecting an additive containing a non-volatile ionic liquid and an ion salt, after the injection of a hole transfer material;    (2) a solar cell comprising the photoelectrode produced by the method (p1); and    (3) a field effect transistor comprising: a conductor layer; an insulating layer; and a semiconductor layer, where the insulating layer comprises a mesoporous inorganic oxide film that is patterned by the patterning method (m1).    DESCRIPTION OF DRAWING(S) - The figure shows a process diagram schematically illustrating step of producing photoelectrode.