A method utilizing a device andor system presented herein for generating alternating current electricity directly from photovoltaic cells utilize an array of photovoltaic cell pairs that are each connected in anti-parallel to form an ac junction. The device also includes a coating film made of a dielectric having a function of storing electric charge and formed on the substrate in such a manner as to cover an upper surface and side surfaces of the gate electrode. A presentation route that follows the leaf nodes of the presentation candidates starting from the root of the tree structure is generated as a presentation scenario for each user.