Infrared Optical up-conversion devices are attracting more and more attentions for their greater capability to convert infrared light to visible light via optical-electrical-optical process, compared with other existing converting technology. The basic idea is to integrate an infrared photodetector with a light-emitting diode (LED) or an organic light-emitting device (OLED), connected in series. The infrared photo-generated electron hole pairs within the absorbing layer of photodetector are injected to the LED (or OLED), resulting in an increase in optical emission at a shorter wavelength and therefore achieving optical up conversion. This paper presents our research and development effort in realizing and perfecting such devices, and mainly focuses on the design, internal semiconductor physics, fabrications, and performances of different optical up-conversion device structures. Moreover, based on the analysis of experimental results, the paper explains the close relationship between internal coefficient and overall upconversion power efficiency.

Infrared (IR) imaging, particularly in the near-IR (NIR) wavelength range, has become increasingly important in many critical applications, such as biomedicine, homeland security, night vision, and semiconductor wafer inspection. [ 1–4 ] Traditional NIR image sensors are based on a 2D InGaAs photodetector (PD) array integrated with a Si readout integrated circuit (ROIC) active matrix array. [ 5,6 ] Due to the incompatibility between the processes for III-V semiconductors (e.g., InGaAs) and Si, separate PD and ROIC arrays must be hybridized together using indium solder bump technology to electrically connect the individual pixels of the two devices together ( Figure 1 a). This “fl ip chip hybridization” technique dramatically increases the cost, and severely limits the size of the image sensors. An alternative approach for imaging is to up-convert the NIR photons to visible light that can be effectively detected by the naked eye or a conventional Si charge-coupled device (CCD), which is mass-produced at low-cost in large formats and with several millions of pixels. [ 7,8 ] Various device architectures for NIR optical up-conversion have been demonstrated. [ 7–13 ] The best performance was demonstrated for a hybrid organic/ inorganic up-conversion device by depositing an organic light-emitting diode (OLED) directly on top of an InGaAs/ InP heterojunction phototransistor (HPT). [ 14,15 ] Such hybrid organic/inorganic devices take advantage of the high quantum effi ciency (QE) of inorganic semiconductors for detection in the IR, and the ease of processing of organic semiconductors combined with their high QE for emission in the visible. [ 15 ] Hybrid organic/inorganic devices are also extremely attractive as the output wavelength can easily be tuned across the visible (and even into the UV or IR) simply by changing the organic emitter. Their sensitivity can also be extended beyond the NIR to much longer wavelengths (e.g., mid-IR and beyond) by adopting alternative inorganic PD designs. [ 16,17 ]

Traditional near infrared (NIR) imaging is realized by a two dimensional InGaAs photodetector (PD) array integrated with a Si readout integrated circuit active matrix. The integration between the two different semiconductor arrays seriously restrains the device size-scalability and leads to high manufacture cost. One alternative approach is to up-convert infrared photons to a shorter wavelength (e.g., 1 mu m or below) that can be effectively detected by a conventional Si detector. Herein, we report a highly simplified single-mesa (pixel-less) hybrid organic/inorganic up-conversion imaging device through the integration of a large area inorganic PD with an organic light emitting diode, which can up-convert a NIR scene to a visiblelight image. By combining the fabricated device with a commercially available camera, we demonstrate the first time pixel-less up-conversion NIR imaging with a spatial resolution of better than 6 mu m. This device has great potential for making low-cost, large-area and high resolution NIR cameras. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We report a highly simplified single-mesa organic/inorganic hybrid near-infrared-to-visible imaging upconversion device (spatial resolution ~10 μm). This device integrates an intrinsic-InGaAs substrate and an organic light emitting diode.

We report an organic/inorganic hybrid optical amplifier with a function of converting infrared light to visible light. This device integrates an InGaAs/InP heterojunction phototransistor (HPT) and an organic light emitting device. (C) 2010 Optical Society of America

A near-infrared (1.5 mu m) to visible light (green) electro-optical upconverter with amplified power gain has been designed and demonstrated. The device was fabricated by direct tandem integration of an organic light emitting diode with an inorganic InGaAs/InP hetero-junction phototransistor. An overall external upconversion power efficiency of 155% was measured at room temperature, demonstrating the utility of hybrid organic/inorganic semiconductor systems.

This paper presents our research and development efforts in realizing and perfecting organic/inorganic photon upconversion devices for wavelengths from near infrared (1.5 μm) region to visible light (green). The basic idea is to integrate an InGaAs/InP photodetector with an organic light emitting diode (OLED), connected in series. The detected photocurrent drives the OLED to emit visible light, thereby achieving the wavelength conversion. We have adopted new strategies to improve the external device efficiency, including insertion of an embedded mirror and integration of a heterojunction phototransistor (HPT) and an OLED. As a result, infrared optical upconversion is demonstrated at room temperature with a built-in electrical gain of 15 from the HPT and an external upconversion efficiency that is improved by one order of magnitude.

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 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 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.

A near-infrared to visible light optical upconverter by the integration of an i-In0.53Ga0.47As/C60 junction and an organic light emitting diode is reported. This device shows the photovoltaic effect of an i-In0.53Ga0.47As/C60 heterojunction and potential application in a pixelless upconversion imaging device.

This paper presents our research and development efforts in realizing and perfecting organic/inorganic photon upconversion devices for wavelengths from near infrared (1.5 μm) region to visible light (green). The basic idea is to integrate an InGaAs/InP photodetector with an organic light emitting diode (OLED), connected in series. The detected photocurrent drives the OLED to emit visible light, thereby achieving the upconversion. A few approaches of integration methods and device designs have been tested.

We report a hybrid organic-inorganic optical upconverter with an embedded metal mirror. The device was fabricated through direct tandem integration of an organic light emitting diode (OLED) with an inorganic InGaAs/InP photodetector, converting 1.5 mu m infrared light to visible light. It was found that the device with an embedded mirror exhibited a low turnon voltage (similar to 3.2 V) and an enhanced efficiency. The ratio of photocurrent-induced with an input power density of 0.67 mW/mm(2) versus dark-current-induced visible light was over 500 at a device bias of 6 V at room temperature. The results show that the embedded mirror at the inorganic-organic interface plays a vital role in the performance enhancement of a hybrid upconverter. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

We report a hybrid organic-inorganic optical upconverter with an embedded mirror, which converts 1.5μm infrared light to visible light. The device was fabricated through direct tandem integration of an organic light-emitting diode with an inorganic InGaAs∕InP photodetector. It was found that the device with an embedded mirror exhibited a low turn-on voltage (∼3.2V) and an enhanced efficiency. The ratio of photocurrent-induced light with an input power density of 0.67mW∕mm2 versus dark-current-induced visible light was over 500 at a device bias of 6V at room temperature. The results show that the embedded mirror at the inorganic-organic interface plays a vital role in the performance enhancement of a hybrid upconverter.