The development of optical devices using organic semiconductor materials, such as organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), and organic photodiodes (OPDs), is actively being pursued. The operational mechanisms of OLEDs, OPVs, and OPDs are essentially inverse processes, and by combining appropriate materials, a single device can exhibit both electrical-To-optical and optical-To-electrical conversion functions. We have been developing organic multifunction devices (MFDs) that possess both functions as a new advancement in organic optical devices. This paper introduces the donor/acceptor (D/ A) stacked MFDs we have been working on recently. © 2025 International Society of Functional Thin Film Materials & Devices (FTFMD).