A photodetector includes a first cell for converting incident light into electric charges, the first cell including a first semiconductor layer, a second semiconductor layer and a first substrate interposing the first semiconductor layer with the second semiconductor layer; and a second cell for converting incident light into electric charges, the second cell including a third semiconductor layer, a fourth semiconductor layer, and a second substrate interposing the third semiconductor layer with the fourth semiconductor layer; wherein the second substrate is larger in thickness than the first substrate.

An optoelectronic assembly includes at least one first component that emits first electromagnetic radiation and at least one first photosensitive component that controls the first component. The first photosensitive component connects in parallel to the first component and has a first radiation-sensitive region in a beam path of the first electromagnetic radiation.

A semiconductor device includes a photodiode, a first transistor, and a second transistor. The photodiode has a function of supplying a charge corresponding to incident light to a gate of the first transistor, the first transistor has a function of accumulating the charge supplied to the gate, and the second transistor has a function of retaining the charge accumulated in the gate of the first transistor. The second transistor includes an oxide semiconductor.

An image sensor as a photoelectric conversion device includes: a lower electrode containing a high-melting-point metal; an upper electrode disposed in a layer higher than the lower electrode; a p-type semiconductor layer and an n-type semiconductor layer disposed between the lower electrode and the upper electrode; and a relay electrode containing the high-melting-point metal. The lower electrode and the relay electrode are formed in the same layer. An intermediate layer as a selenized film of the high-melting-point metal is formed on the lower electrode.