▎ 摘　　要

NOVELTY - Photo transistor comprises a gate electrode disposed on a substrate, a gate insulating layer that electrically insulates the gate electrode, a first active layer overlapping the gate electrode and including metal oxide, the gate insulating layer being disposed between the gate electrode and the first active layer, a second active layer disposed on the first active layer and including selenium and a source electrode and a drain electrode respectively electrically connected to the second active layer. USE - Photo transistor used in OLED display device (claimed). ADVANTAGE - The photo transistor is capable of improving a light absorption rate in a visible wavelength band, improve light sensing characteristics, and also improve the photoresponsibity, photosensitivity and detectivity of the photo transistor. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a display device, which comprises a substrate including a transmissive region and a light emission region, a transistor layer disposed on the substrate and including a first transistor and a second transistor, the first transistor including a gate electrode, a first active layer including metal oxide, a second active layer including selenium and source and drain electrodes, a light emitting element layer disposed on the transistor layer and including a first electrode and a touch sensor disposed on the light emitting element layer and including electrodes.