There remains a critical need for large‐area imaging technologies that operate in the shortwave infrared spectral region. Upconversion imagers that combine photo‐sensing and display in a compact ...structure are attractive since they avoid the costly and complex process of pixilation. However, upconversion device research is primarily focused on the optical output, while electronic signals from the imager remain underutilized. Here, an organic upconversion imager that is efficient in both optical and electronic readouts, extending the capability of human and machine vision to 1400 nm, is designed and demonstrated. The imager structure incorporates interfacial layers to suppress non‐radiative recombination and provide enhanced optical upconversion efficiency and electronic detectivity. The photoresponse is comparable to state‐of‐the‐art organic infrared photodiodes exhibiting a high external quantum efficiency of ≤35% at a low bias of ≤3 V and 3 dB bandwidth of 10 kHz. The large active area of 2 cm2 enables demonstrations such as object inspection, imaging through smog, and concurrent recording of blood vessel location and blood flow pulses. These examples showcase the potential of the authors’ dual‐readout imager to directly upconvert infrared light for human visual perception and simultaneously yield electronic signals for automated monitoring applications.
This work presents an organic upconversion imager with efficient electronic and optical dual‐readouts to detect infrared radiation to 1400 nm. The key to improving efficiency results from the incorporation of an interlayer that suppressed non‐radiative recombination. The single pixel imager combines photo‐sensing and display, enabling demonstrations such as simultaneous recordings of blood vessel location and blood flow pulses.
An effective method for reducing interelectrode shorting in silver nanowire (AgNW) based organic solar cells is reported. The method is applied to standard and inverted devices based on ...poly(3‐hexylthiophene) and 6,6‐phenyl‐C61‐butyric acid methyl ester. The best results are obtained using an inverted architecture with a 200 nm buffer layer of nanostructured titania (TiOx) on top of the AgNWs, yielding power conversion efficiencies of up to 3.5%.
Detection of light in the near‐infrared (NIR) and shortwave infrared (SWIR) spectral range is essential for the wide practical applications of biometrics, surveillance, machine vision, etc., in which ...organic molecules have gained growing interest as the potential sensing materials. In this study, the newly synthesized donor–acceptor type copolymers consisting of 1,2,5thiadiazolo3,4‐gquinoxaline core unit with phenyl pendant groups as the acceptor and thiophene unit as the donor for achieving high‐efficiency organic SWIR photodetectors are presented. A further variation of the alkoxy chain lengths in the core unit allows the optimized device to exhibit a high external quantum efficiency of 19.5%–21.7% at 1200 nm under the low reverse bias of −1 V, leading to a high detectivity up to 2.96 × 1010 Jones for the spectral range beyond 1 µm. This further suggests the possible origin of the molecular structure‐dependent device performance in terms of the molecular stacking, morphological changes, and charge‐transporting properties in the bulk heterojunction blends.
Efficient 1,2,5thiadiazolo3,4‐gquinoxaline polymer‐based shortwave infrared organic photodiodes are demonstrated. By tuning the alkoxy chain length in the p‐type polymer core and blending with a non‐fullerene n‐type acceptor, a high external quantum efficiency of 19.5%–21.7% and a high specific detectivity of 8.17 × 109 – 2.96 × 1010 Jones with −1 V reverse bias at 1200 nm wavelength are achieved.
This review is written to introduce infrared photon detectors based on solution-processable semiconductors. A new generation of solution-processable photon detectors have been reported in the past ...few decades based on colloidal quantum dots, two-dimensional materials, organics semiconductors, and perovskites. These materials offer sensitivity within the infrared spectral regions and the advantages of ease of fabrication at low temperature, tunable materials properties, mechanical flexibility, scalability to large areas, and compatibility with monolithic integration, rendering them as promising alternatives for infrared sensing when compared to vacuum-processed counterparts that require rigorous lattice matching during integration. This work focuses on infrared detection using disordered semiconductors so as to articulate how the inherent device physics and behaviors are different from conventional crystalline semiconductors. The performance of each material family is summarized in tables, and device designs unique to solution-processed materials, including narrowband photodetectors and pixel-less up-conversion imagers, are highlighted in application prototypes distinct from conventional infrared cameras. We share our perspectives in examining open challenges for the development of solution-processable infrared detectors and comment on recent research directions in our community to leverage the advantages of solution-processable materials and advance their implementation in next-generation infrared sensing and imaging applications.
To achieve high detectivity in infrared detectors, it is critical to reduce the device noise. However, for non-crystalline semiconductors, an essential framework is missing to understand and predict ...the effects of disorder on the dark current. This report presents experimental and modeling studies on the noise current in exemplar organic bulk heterojunction photodiodes, with 10 donor–acceptor combinations spanning wavelength between 800 and 1600 nm. A significant reduction of the noise and higher detectivity were found in devices using non-fullerene acceptors (NFAs) in comparison to those using fullerene derivatives. The low noise in NFA blends was attributed to a sharp drop off in the distribution of bandtail states, as revealed by variable-temperature density-of-states measurements. Taking disorder into account, we developed a general physical model to explain the dependence of thermal noise on the effective bandgap and bandtail spread. The model provides theoretical targets for the maximum detectivity that can be obtained at different detection wavelengths in inherently disordered infrared photodiodes.
Achieving high‐performance near‐infrared (NIR) photodiodes is in great demand for potential applications like biometrics, security, artificial vision, biomedical imaging, etc. Herein, silicon ...naphthalocyanine (SiNc) small molecule‐based NIR photodiodes with narrowband absorption are presented. The optimized photodiode by varying the axial ligand in the SiNc molecules exhibits a high external quantum efficiency of 76.6% at 795 nm with narrow full width at half maximum of 80 nm, a very low dark current of 1.07 nA cm−2 at a reverse bias of −3 V, and the resultant detectivity of 5.66 × 1012 Jones. Further increase of the detectivity up to 1013 Jones is obtained by modulating the applied bias to −1 V, which is among the highest values of organic NIR detectors reported to date. The SiNc‐based photodiodes are further characterized by temporal response, linear dynamic range, etc., and shown to be stable in high humidity for over a month and in a remarkably wide temperature range (−55 to 125 °C). It is highly likely that the developed SiNc‐based photodiodes can be applicable to a wide variety of NIR sensor platforms.
High performance near‐infrared (NIR) organic photodiodes with silicon naphthalocyanine small molecules are demonstrated. The optimized devices exhibit high efficiency over 76% in the NIR wavelength, low noise characteristics, and long‐term reliability in humidity condition as well as a wide temperature range, which can be applicable to a variety of NIR sensor platforms.
There are growing opportunities and demands for image sensors that produce higher-resolution images, even in low-light conditions. Increasing the light input areas through 3D architecture within the ...same pixel size can be an effective solution to address this issue. Organic photodiodes (OPDs) that possess wavelength selectivity can allow for advancements in this regard. Here, we report on novel push–pull D−π–A dyes specially designed for Gaussian-shaped, narrow-band absorption and the high photoelectric conversion. These p-type organic dyes work both as a color filter and as a source of photocurrents with linear and fast light responses, high sensitivity, and excellent stability, when combined with C60 to form bulk heterojunctions (BHJs). The effectiveness of the OPD composed of the active color filter was demonstrated by obtaining a full-color image using a camera that contained an organic/Si hybrid complementary metal-oxide-semiconductor (CMOS) color image sensor.
Inverted bulk heterojunction solar cells are fabricated using a conjugated polyelectrolyte (PFN) as a cathode interlayer. Enhanced photovoltaic performance is achieved by adjusting the PFN thickness. ...Measurements of the optical transmittance, cathode work function (via UPS) and surface atomic composition (via XPS) provide insights into this optimization. Drift‐diffusion simulations point to a reduction in recombination of holes at the cathode as the main cause for improving Voc.
This work studied a series of infrared detectors comprised of organic bulk heterojunctions to explain the origin of their broadband spectral response from the visible to the infrared spanning 1 to 8 ...μm and the transition from photonic to bolometric operation. Through comparisons of the detector current and the sub-bandgap density of states, the mid- and long-wave infrared response was attributed to charge trap-and-release processes that impact thermal charge generation and the activation energy of charge mobility. We further demonstrate how the sub-bandgap characteristics, mobility activation energy, and effective bandgap are key design parameters for controlling the device temperature coefficient of resistance, which reached up to −7%/K, better than other thin-film materials such as amorphous silicon and vanadium oxide.
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