Positive-feedback organic light-emitting diodes and upconverters

Organic light-emitting diodes (OLEDs) are among the most successful organic electronic devices so far. They currently dominate the mobile display market and are expanding into a broad range of lighting, automotive and wearable device applications. Here we introduce a new class of organic light-emitting device that exhibits bistability owing to positive photonic feedback between an organic photodiode and a tandem OLED integrated in the same layer stack. These unusual devices display giant hysteresis in both their current and light emission, and respond sensitively to low-level external illumination, enabling optoelectronic upconversion with 100-fold photon-to-photon gain. Given their compatibility with existing OLED materials and manufacturing lines, these devices could find near-term use in new types of display and upconversion imaging applications, as well as offer a new platform for neuromorphic optoelectronics and image recognition. Integrating an organic photodiode with a tandem OLED enables positive photonic feedback that results in bistable behaviour. Devices show giant hysteresis in their current-voltage-luminance characteristic and upconversion of near-infrared to visible light with 100-fold photon-to-photon gain.