Near-IR Optical Upconverter With Integrated Heterojunction Phototransistor and Organic Light-Emitting Diode

In this letter, we report a near-infrared (NIR) optical upconverter consisting of an integrated InGaAs–InP heterojunction phototransistor (HPT) with an organic light-emitting diode (OLED), which converts 1.5-$\mu\hbox{m}$ IR light to visible light with a built-in electrical gain. The device was fabricated through direct tandem integration of an OLED with an inorganic InGaAs–InP HPT. Incoming 1.5-$\mu\hbox{m}$ optical radiation is absorbed by the HPT, generating an amplified photocurrent. The resultant photocurrent drives the OLED that emits at 545 nm. Upconversion is demonstrated at room temperature with a gain of 15 from the HPT and an overall external upconversion efficiency of 0.15 W/W.