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Device performance of the PTB7-Th:COTIC-4F OUD (top emission). (A) Current density-voltage characteristics as a function of 940-nm laser intensity. (B) Upconversion luminance of the device upon the same infrared stimulus. (C) LDR of the upconversion luminance at different bias voltages. The dash lines represent the bias-dependent leakage luminance (without infrared illumination). The solid gray line represents the ideal case (slope equals one). (D) The transmittance spectrum (rainbow waterfall) and EQE spectra recorded from the semitransparent top cathode. (E) The infrared-to-visible upconversion efficiency of the device under various infrared power densities. (F) Normalized electroluminescent spectra of the top-emissive OUD and OUD in standard structure (Fig. 3).
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Crystalline photodiodes remain the most viable infrared sensing technology of choice, yet the opacity and the limitation in pixel size reduction per se restrict their development for supporting high-resolution in situ infrared images. In this work, we propose an all-organic non-fullerene–based upconversion device that brings invisible infrared sign...
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... infrared photon can be figured with the thin-film deposition of an OLED on the BHJ blend accordingly (Materials and Methods). S4). The strong correlation between the infrared intensity and the upconversion luminance substantiated the strategy of using BCzPh:CN-T2T cohost phosphorescence light-emissive system (8). ...
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... top-emissive structure. Although further reducing the alloy thickness can, on the one hand, achieve higher transmittance in visible frequency, it undermines the wavelength selectivity for the reflective infrared signal, as well as the uniformity concern on the other hand. Hence, an AVT approaching 60% was achieved by the overall device stacking (Fig. 4). The device managed an EQE of 49.95% at the wavelength of 940 nm under an external bias voltage of 8.0 V with a transmittance loss of 15.14% at the same wavelength (Fig. 4D). As a matter of fact, Cu:Ag alloy cathode reflected only partial incoming infrared photons, and more than half of the upconversion luminance was released from the ...
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... selectivity for the reflective infrared signal, as well as the uniformity concern on the other hand. Hence, an AVT approaching 60% was achieved by the overall device stacking (Fig. 4). The device managed an EQE of 49.95% at the wavelength of 940 nm under an external bias voltage of 8.0 V with a transmittance loss of 15.14% at the same wavelength (Fig. 4D). As a matter of fact, Cu:Ag alloy cathode reflected only partial incoming infrared photons, and more than half of the upconversion luminance was released from the indium tin oxide (ITO) anode (i.e., favorable AVT of typical ITO substrate for visible light out-coupling). The efficiency of the top-emissive device was three times smaller ...
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... than half of the upconversion luminance was released from the indium tin oxide (ITO) anode (i.e., favorable AVT of typical ITO substrate for visible light out-coupling). The efficiency of the top-emissive device was three times smaller than the standard structure, accounting for a maximum η p-p of 3.7% after excluding the luminance under dark (Fig. 4E). Although the loss can be restored by increasing the CGL thickness and selectively regulating the light path (9), we constructed the transparent device following the standard device for consistency. Besides, the transparency of the device can be lost after integrating a cold mirror. The top-emissive device could track the infrared ...
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... and selectively regulating the light path (9), we constructed the transparent device following the standard device for consistency. Besides, the transparency of the device can be lost after integrating a cold mirror. The top-emissive device could track the infrared power density down to submicrowatt per centimeter square level in linear ( Fig. 4C) with an electroluminescent spectrum similar to that of the standard device (Fig. ...
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... device following the standard device for consistency. Besides, the transparency of the device can be lost after integrating a cold mirror. The top-emissive device could track the infrared power density down to submicrowatt per centimeter square level in linear ( Fig. 4C) with an electroluminescent spectrum similar to that of the standard device (Fig. ...
Citations
... S26 and the Supplementary Materials), which may be attributed to the light outcoupling loss caused by the reabsorption of the OPD subunit to the emitted light. Meanwhile, it is anticipated that the SWIR upconversion with color selectivity and higher efficiency can be achieved by integrating OLED emitting visible light with varying wavelength (58) or higher EQE EL (59). The imaging LDR (I-LDR) of the OUD, one of the key metrics for high-quality imaging, was calculated to be 85 dB (Fig. 4E), according to I-LDR = 20log(L upper /L lower ) (where L upper and L lower are the upper and the lower luminance within the linear region of L-V curve, respectively), which ranks among the highest values of reported NIR OUDs (60) and is attributed to high sensitivity and η p-p of the OUD. ...
Short-wavelength infrared (SWIR) light detection plays a key role in modern technologies. Emerging solution-processed organic semiconductors are promising for cost-effective, flexible, and large-area SWIR organic photodiodes (OPDs). However, the spectral responsivity ( R ) and specific detectivity ( D *) of SWIR OPDs are restricted by insufficient exciton dissociation and high noise current. In this work, we synthesized an SWIR small molecule with a spectral coverage of 0.3 to 1.3 micrometers peaking at 1100 nanometers. The photodiode, with optimized exciton dissociation, charge injection, and SWIR transmittance, achieves a record high R of 0.53 ampere per watt and D * of 1.71 × 10 ¹³ Jones at 1110 nanometers under zero bias. The D * at 1 to 1.2 micrometers surpasses that of the uncooled commercial InGaAs photodiode. Furthermore, large-area semitransparent all-organic upconversion devices integrating the SWIR photodiode realized static and dynamic SWIR-to-visible imaging, along with excellent upconversion efficiency and spatial resolution. This work provides alternative insights for developing sensitive organic SWIR detection.
... Recently, Tao et al. constructed a high-efficiency and low-energy consuming all-organic UCD by combining the solution process and thermal evaporation. 1 Ternary hybrid heterojunctions are first introduced to prepare the NIR photosensitive layer, which effectively enhances the photon-induced exciton generation and dissociation in the device. As a result, a low turn-on voltage of 1.56 V and a high η p-p (from 895 to 524 nm) of up to 12.92% were realized in the UCD. ...
... The visualization detection of near-infrared (NIR) light has demonstrated remarkable potential in noninvasive biomedicine imaging, night vision, and environmental and health monitoring. [1][2][3][4][5][6] The NIR-to-visible upconversion devices (UCDs), through monolithic integration of a NIR sensing photodetector (PD) unit and a visible lightemitting unit, offer an appealing tool that can be used to reify the NIR light into vision images in a simple and low-cost manner. [7][8][9][10][11] In contrast with the traditional NIR imaging technology, the UCD is a lowcost and pixel-less visual imaging technology, which does not rely on the complicated readout integrated circuit and pixel array that requires delicate lithography technology. ...
... All organic, [16][17][18][19] organic/inorganic, 20,21 quantum dots (QDs), 12,22,23 and perovskite materials 9,15 have been used as NIR absorbers and/or light-emitting layers in NIR-to-visible UCDs. In the meantime, various device architectures, including hole-or electron-driven configuration, 24,25 topemitting structure (transparent cathode), 2,21,25,26 and multiple unit stacking of LED/PD/LED, 27,28 have been adopted to improve the performance of NIR-to-visible UCDs. Until now, almost all the reported UCDs emit only a fixed color (it is green in most cases) based on a monochrome color light-emitting unit. ...
... As a result, the luminance and contrast ratio are as high as 4 Â 10 3 cd/m 2 and More importantly, another striking feature of the present UCDs is that the visible emission color varies with different applied bias voltage (or current), in contrast to previously reported UCDs. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] As shown in Fig. 3(c), red emission is dominant at low voltages, while green emission is dominant at high voltages. The turning point of this change is around 10 V [see Fig. 3(b)]. ...
Color-tunable near-infrared (NIR)-to-visible upconversion devices (UCDs) that correlate the NIR power intensity with the visible emission color are highly desired and hold promise for interactive signal visualization in intelligent optoelectronic devices. In this work, solution-processed color-tunable UCDs integrating a NIR sensing photodetector unit and a color-tunable quantum dot (QD) light-emitting unit are demonstrated. We mixed the red and green QDs in a single emissive layer (EML) for multi-color emission from the UCDs, which is quite different from the previously reported work that used multiple EMLs with different colors. The image color of the resulting color-tunable UCDs can be modulated by bias voltage and driving current and shows a wide color-span range from red to green as the NIR intensity increases. Finally, we present a qualitative correlation between the incident NIR power intensity and the visible emission color, which enables colorful visualization detection of NIR light.
... UCDs are typically comprised of an NIR detection unit (IDU) and a visible light emission unit (VEU) in a back-to-back mode. The two units usually share the same carrier transport layer 10,11 . Unlike the traditional upconversion of two or more low-energy photons into one high-energy photon (anti-Stokes conversion), the working mechanism of UCDs can be simpli ed as the up-conversion of a low-energy photon into a highenergy photon through electrical assistance 9,12 . ...
Infrared upconversion devices (UCDs) enable NIR imaging without array and readout circuits, making them desirable for portable sensor, imaging and monitoring. However, the exorbitant cost and high operating voltages associated with vacuum-deposited materials, which are usually employed in high-performance UCDs, restrict their application in flexible systems. Here, we report a solution-processed upconversion device (s-UCD), which is composed of detector and emitter, with high conversion efficiency (11.9%) and low turn-on voltage (1.2 V) achieved by rigorous device structure design and interlayer engineering. We investigated the role of the electron blocking layer in s-UCDs, and a peak luminance of 5500 cd m ⁻² and a luminance on-off ratio of 95,000 were achieved. Our s-UCDs exhibit high resolution, microsecond response time and are compatible with flexible substrates. With the high-performance large-area s-UCDs, we further performed direct non-invasive transmission-based bioimaging applications with high quality of bioimaging. Owing to the solution-processed fabrication, it is believed that our s-UCD imaging system offers potential applications for portable low-cost non-invasive tissue analysis, disease diagnosis, and virtual reality.
Infrared upconversion devices (UCDs) enable NIR imaging without array and readout circuits, making them desirable for portable sensor, imaging and monitoring. However, the exorbitant cost and difficulties in fabrication associated with vacuum‐deposited materials, which are usually employed in high‐performance UCDs, restrict their application in flexible‐stretchable systems. Here, a solution‐processed upconversion device (s‐UCD), which is composed of detector and emitter, with high conversion efficiency and low turn‐on voltage achieved by device structure design and interlayer engineering is reported. The role of the electron blocking layer is investigated in s‐UCDs, and a peak luminance of 5,500 cd m⁻² @7 V and a luminance on‐off ratio of 110000 @5.25 V are achieved. The s‐UCDs exhibit high resolution, microsecond response time and are compatible with flexible substrates. With the high‐performance large‐area s‐UCDs, direct non‐invasive transmission‐based bioimaging applications with high quality of bioimaging are further performed. It is believed that the s‐UCD imaging system offers potential applications for portable low‐cost non‐invasive tissue analysis, disease diagnosis, and virtual reality.
Sensitive detection of shortwave infrared (SWIR) light using organic dyes will be a significant advance toward many applications in industry and research. Furthermore, from a fabrication and optimization view, photogeneration of charges in diodes consisting of a single dye layer will be highly attractive. However, SWIR dyes are scarce and organic photodiodes usually utilize a donor–acceptor materials combination to split excitons into charges. Here, it is demonstrated that single‐component layers of several SWIR squaraine dyes operate as efficient photodetectors, with peak external quantum efficiency > 40% beyond 1000 nm and sensitivity out to 1300 nm. Photocurrents show a superlinear dependence on reverse bias. It is shown that this results from a field‐assisted exciton dissociation mechanism, and not from field‐dependent charge injection or extraction. SWIR photodiodes are combined with organic light‐emitting diodes to fabricate upconversion photodetectors – devices that convert SWIR photons directly into visible light. Upconverters are characterized by a low turn‐on voltage (1.5 V) and a high luminance contrast (on‐off ratio 16 000) and SWIR‐to‐visible (λ = 575 nm) photon conversion efficiency (1.85%). Upconversion photodetectors emerge as a promising alternative to the current inorganic‐based imaging technology.
Solution‐processed photodetectors have emerged as promising candidates for next‐generation of visible‐near infrared (vis–NIR) photodetectors. This is attributed to their ease of processing, compatibility with flexible substrates, and the ability to tune their detection properties by integrating complementary photoresponsive semiconductors. However, the limited performance continues to hinder their further development, primarily influenced by the difference of charge transport properties between perovskite and organic semiconductors. In this work, a perovskite‐organic bipolar photodetectors (PDs) is introduced with multispectral responsivity, achieved by effectively managing charges in perovskite and a ternary organic heterojunction. The ternary heterojunction, incorporating a designed NIR guest acceptor, exhibits a faster charge transfer rate and longer carrier diffusion length than the binary heterojunction. By achieving a more balanced carrier dynamic between the perovskite and organic components, the PD achieves a low dark current of 3.74 nA cm⁻² at −0.2 V, a fast response speed of <10 µs, and a detectivity of exceeding 10¹² Jones. Furthermore, a bioinspired retinotopic system for spontaneous chromatic adaptation is achieved without any optical filter. This charge management strategy opens up possibilities for surpassing the limitations of photodetection and enables the realization of high‐purity, compact image sensors with exceptional spatial resolution and accurate color reproduction.
Near‐infrared (NIR) to visible upconversion devices (UCDs) provide a viable and cost‐effective way for NIR visualization and pixel‐less imaging techniques. An excellent electrical connection between the NIR detection unit and the visible emission unit in the UCD is one of the prerequisites for achieving efficient upconversion performance. In this study, a low temperature‐ and solution‐processed nickel oxide (NiOx) interconnecting layer (ICL) with high hole mobility and favorable energy levels is demonstrated to decouple the trade‐off between photosignal and photonoise in the UCDs. The use of such a NiOx ICL suppresses intrinsic visible emission in the dark (photonoise) but enhances visible light output under NIR illumination (photosignal) by triggering an efficient charge injection in the UCDs. As a result, a hybrid UCD monolithically integrating an organic NIR photodetector and a visible quantum dot light‐emitting diode via the NiOx ICL achieves excellent performance, exhibiting an ultralow turn‐on voltage as low as 1.6 V, a high luminance close to 6.3 × 10³ cd m⁻², a wide operation voltage window up to 7.4 V, and a high contrast ratio reaching 5 × 10⁴. The resulting UCD is also used for imaging demonstrations showing clear visible images of the NIR targets, which paves the way for practical applications.
