Positive Feedback Organic-on-Silicon Upconversion Devices

Positive feedback upconversion devices exhibit optoelectronic bistability and large photon-to-photon gain that can benefit applications ranging from night vision to neuromorphic image classification. Here, a hybrid device architecture is introduced that integrates a tandem organic light-emitting diode (OLED) on top of an organic/Si heterojunction photodiode. These devices respond to near infrared light at wavelengths up λ ≈ 1.1 µm and exhibit a peak photon-to-photon upconversion gain of 9x when triggered with input light intensity <1 µW cm^-2. It is found that minimizing the capacitance of the photodiode is important for maximizing the upconversion response speed of the device, and that electrical crosstalk in pixelated devices must be overcome to prevent cascading effects where one activated pixel triggers many others. These results mark an important step for optoelectronic upconverters that can be integrated with Si microelectronics, and they establish a path to extend the responsivity further into the near infrared by moving to other inorganic semiconductor platforms such as Ge or InGaAs.