Figure 5.

Layouts of upconverter architectures with increased NIR-to-visible photon conversion efficiency. Several crucial charge-blocking, -transporting and -generating interfacial layers are omitted in these simplified pictures for clarity. a) In a tandem upconverter the photodetector is sandwiched between two emitter layers, electrons, as well as holes, are harvested to generate visible light. b) A tandem OLED emits two visible photons per one photogenerated charge. c) A photodetector with a gain injects more than one hole into the emitter layer per one photogenerated charge.