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Efficiently solving combinatorial optimization problems (COPs) such as Max-Cut is challenging because the resources required increase exponentially with the problem size. This study proposes a hardware-friendly method for solving the Max-Cut problem by implementing a spiking neural network (SNN)-based Boltzmann machine (BM) in neuromorphic hardware systems. To implement the hardware-oriented version of the spiking Boltzmann machine (sBM), the stochastic dynamics of leaky integrate-and-fire (LIF) neurons with random walk noise are analyzed, and an innovative algorithm based on overlapping time windows is proposed. The simulation results demonstrate the effective convergence and high accuracy of the proposed method for large-scale Max-Cut problems. The proposed method is validated through successful hardware implementation on a 6-transistor/2-resistor (6T2R) neuromorphic chip with phase change memory (PCM) synapses. In addition, as an expansion of the algorithm, several annealing techniques and bias split methods are proposed to improve convergence, along with circuit design ideas for efficient evaluation of sampling convergence using cell arrays and spiking systems. Overall, the results of the proposed methods demonstrate the potential of energy-efficient and hardware-implementable approaches using SNNs to solve COPs. To the best of the author's knowledge, this is the first study to solve the Max-Cut problem using an SNN neuromorphic hardware chip., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

Purpose: This study was performed to assess the clinical validity and accuracy of a deep learning-based automatic landmarking algorithm for cone-beam computed tomography (CBCT). Three-dimensional (3D) CBCT head measurements obtained through manual and automatic landmarking were compared., Materials and Methods: A total of 80 CBCT scans were divided into 3 groups: non-surgical (39 cases); surgical without hardware, namely surgical plates and mini-screws (9 cases); and surgical with hardware (32 cases). Each CBCT scan was analyzed to obtain 53 measurements, comprising 27 lengths, 21 angles, and 5 ratios, which were determined based on 65 landmarks identified using either a manual or a 3D automatic landmark detection method., Results: In comparing measurement values derived from manual and artificial intelligence landmarking, 6 items displayed significant differences: R U6CP-L U6CP, R L3CP-L L3CP, S-N, Or&#95;R-R U3CP, L1L to Me-GoL, and GoR-Gn/S-N ( P <0.05). Of the 3 groups, the surgical scans without hardware exhibited the lowest error, reflecting the smallest difference in measurements between human- and artificial intelligence-based landmarking. The time required to identify 65 landmarks was approximately 40-60 minutes per CBCT volume when done manually, compared to 10.9 seconds for the artificial intelligence method (PC specifications: GeForce 2080Ti, 64GB RAM, and an Intel i7 CPU at 3.6 GHz)., Conclusion: Measurements obtained with a deep learning-based CBCT automatic landmarking algorithm were similar in accuracy to values derived from manually determined points. By decreasing the time required to calculate these measurements, the efficiency of diagnosis and treatment may be improved., Competing Interests: Conflicts of Interest: None, (Copyright © 2024 by Korean Academy of Oral and Maxillofacial Radiology.)

Despite decades of research, the dominant charge generation mechanism in organic bulk heterojunction (BHJ) devices is not completely understood. While the local dielectric environments of the photoexcited molecules are important for exciton dissociation, conventional characterizations cannot separately measure the polarizability of electron-donor and electron-acceptor, respectively, in their blends, making it difficult to decipher the spectrally different charge generation efficiencies in organic BHJ devices. Here, by spectrally resolved electroabsorption spectroscopy, we report extraction of the excited state polarizability for individual donors and acceptors in a series of organic blend films. Regardless of the donor and acceptor, we discovered that larger exciton polarizability is linked to larger π-π coherence length and faster charge transfer across the heterojunction, which fundamentally explains the origin of the higher charge generation efficiency near 100% in the BHJ photodiodes. We also show that the molecular packing of the donor and acceptor influence each other, resulting in a synergetic enhancement in the exciton polarizability.

Organic solar cells based on bulk heterojunctions (BHJs) are attractive energy-conversion devices that can generate electricity from absorbed sunlight by dissociating excitons and collecting charge carriers. Recent breakthroughs attained by development of nonfullerene acceptors result in significant enhancement in power conversion efficiency (PCEs) exceeding 17%. However, most of researches have focused on pursuing high efficiency of small-area (<1 cm 2 ) unit cells fabricated usually with spin coating. For practical application of organic photovoltaics (OPVs) from lab-scale unit cells to industrial products, it is essential to develop efficient technologies that can extend active area of devices with minimized loss of performance and ensured operational stability. In this progress report, an overview of recent advancements in materials and processing technologies is provided for transitioning from small-area laboratory-scale devices to large-area industrial scale modules. First, development of materials that satisfy requirements of high tolerability in active layer thickness and large-area adaptability is introduced. Second, morphology control using various coating techniques in a large active area is discussed. Third, the recent research progress is also underlined for understanding mechanisms of OPV degradation and studies for improving device long-term stability along with reliable evaluation procedures., (© 2020 Wiley-VCH GmbH.)

A fully water-based patterning method for polymer semiconductors was developed and utilized to realize high-precision lateral patterning of various polymers. Water-borne polymer colloids, wherein hydrophobic polymers are dispersed in water with the assistance of surfactant molecules, possess a hydrophilic surface when printed onto a substrate. When this surface is exposed to a washing molecule, the surface of the polymer film recovers its original hydrophobic nature. Such surfactant-induced solubility control (SISC) enables environmentally benign, water-processed, and high-precision patterning of various polymer semiconductors with totally different solubilities, so that fully water-processed polymer organic image sensors (OISs) can be realized. B-/G-/R-selective photodiodes with a pixel size of 100 μm × 100 μm were fabricated and patterned by this water-based SISC method, leading to not only high average specific detectivity values (over 10 12 Jones) but also narrow pixel-to-pixel deviation. Thanks to the superiority of the SISC method, we demonstrate the image capturing ability of OISs without B-/G-/R-color filters, from a fully water-based fabrication process.

A strategically designed polymer semiconductor thin film morphology with both high responsivity to the specific gas analyte and high signal transport efficiency is reported to realize high-performance flexible NOx gas sensors. Breath-figure (BF) molding of polymer semiconductors enables a finely defined degree of nano-porosity in polymer films with high reproducibility while maintaining high charge carrier mobility characteristics of organic field effect transistors (OFETs). The optimized BF-OFET with a donor-acceptor copolymer exhibits a maximum responsivity of over 104%, sensitivity of 774% ppm-1, and limit of detection (LOD) of 110 ppb against NO at room temperature. When tested across at NO concentrations of 0.2-10 ppm, the BF-OFET gas sensor exhibits a response time of 100-300 s, which is suitable for safety purposes in practical applications. Furthermore, BF-OFETs show a high reproducibility as confirmed by statistical analysis on 64 independently fabricated devices. The selectivity of NOx analytes is tested by comparing the sensing ability of BF-OFETs with those of other reducing gases and volatile organic compounds; the BF-OFET gas sensor platform monitors specific gas analytes based on their polarity and magnitude of sensitivity. Finally, flexible BF-OFETs conjugated with plastic substrates are demonstrated and they exhibit a sensitivity of 500% ppm-1 and a LOD of 215 ppb, with a responsivity degradation of only 14.2% after 10 000 bending cycles at 1% strain.

A molecular approach to achieve wide linear dynamic range (LDR) and near-infrared (NIR)-selective thin film organic photodiodes (OPDs) with high detectivity is reported. Comparative studies based on two NIR-selective polymers are systematically investigated: the commercially available poly[(4,4'-bis(2-ethylhexyl)cyclopenta[2,1- b :3,4- b ']dithiophene)- alt -(benzo[ c ][1,2,5]thiadiazole)] (PCPDTBT) and the synthesized poly[(4,4'-(bis(hexyldecylsulfanyl)methylene)cyclopenta[2,1- b :3,4- b ']-dithiophene)- alt -(benzo[ c ][1,2,5]thiadiazole)] (PCPDTSBT). The introduction of sp 2 -hybridized side chains in the PCPDTSBT structure can improve chain planarity and thus intermolecular interactions, as confirmed by Raman spectroscopy and grazing incidence X-ray diffraction studies. The favorable crystalline orientation of PCPDTSBT leads to enhanced photocurrent and suppressed noise current, compared to that of PCPDTBT, followed by a sharp increase in the specific detectivity of PCPDTSBT-based NIR OPDs by 1.54 × 10 12 Jones. The physics behind PCPDTSBT is analyzed employing optical simulation, temperature-dependent junction analyses, and Mott-Schottky analysis. Furthermore, it is found that PCPDTSBT possesses an exceptional nonsaturation photocurrent, which leads to a wide LDR of 128 dB. This study shows the possibility of realizing thin film NIR-selective OPDs using synthetic approaches.

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study. By employing PCZ-Th-DPP as a photoactive layer of Schottky OPD, to fully match its absorption characteristic to the spectral response of the red-selective OPD, we demonstrate a genuine red-selective specific detectivity in the order of 10 12 Jones while maintaining a thin active layer thickness of ∼300 nm. This work demonstrates the possibility of realizing a full color image sensor with a synthetic approach to the constituting active layers without optical manipulation.

Here, a smart strategy for decreasing the active layer thickness of the organic photodiode down to 70 nm is demonstrated by utilizing a trap-assisted photomultiplication mechanism with the optimized chemical composition. Despite the presence of a high dark current, dramatically enhanced external quantum efficiency (EQE) via photomultiplication can allow significantly reduced active layer thickness, yielding high detectivity comparable to that of conventional Si. To achieve this, a spatially confined and electrically isolated optical sensitizer, 2,2'-((2 Z,2' Z)-((4,4,9,9-tetrahexyl-4,9-dihydro- s-indaceno[1,2- b:5,6- b']dithiophene-2,7-diyl)bis(methanylylidene))bis(3-oxo-2,3-dihydro-1 H-indene-2,1-diylidene))dimalononitrile (IDIC) was introduced strategically between a hole transport active layer and a cathode. A nonfullerene acceptor, IDIC, turned out to be a much more efficient sensitizer than the conventional fullerene-based acceptors, as confirmed by the effective lowering of the Schottky barrier under illumination, as well as the highest EQE exceeding 130 000%. Due to its favorable electronic structure as well as two-dimensional molecular structure, a high detectivity over 10 12 Jones was successfully demonstrated while maintaining the active layer thickness as 70 nm.

We introduce a strategic approach to synthesize covalntly cross-linked carbon nanotube (CNT)-polymer nanocomposites, which can be applied as a free-standing and flexible organic thermoelectric generator film. Esterification of polyvinyl alcohol (PVA) to render PVA-COOH followed by an amide reaction with single-walled CNTs (SWCNTs) functionalized with amino groups (SWCNT-NH 2 ) yielded a covalently grafted PVA/SWCNT composite film with an excellent dispersion of SWCNTs within the polymer matrix as confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy. This amide reaction could be further optimized with the addition of a small amount of Triton™ X-100, which resulted in a better dispersion of SWCNT prior to the amide condensation reaction. Consequently, a covalently cross-linked PVA/SWCNT composite film showed better Seebeck coefficients than those of previously reported non-covalently, physically wrapped polymer/CNT composite films, resulting in a high power factor up to 275 μW m -1 K -2 . Furthermore, a covalent amide-linking between PVA and SWCNT yielded a free-standing film (30 × 30 mm) with excellent flexibility and notable shelf stability as confirmed by negligible changes in thermoelectric parameters after bending test for 10 000 times with a bending radius of 2 mm and also shelf stability test in ambient condition without any passivation layer for 30 d.

A facile and strategic junction tuning technology is reported to boost self-powered organic Schottky photodiode (OPD) performances by synergetic contributions of reactive dedoping effects. It is shown that dedoping poly(3-hexylthiophene-2,5-diyl) (P3HT) films with 1-propylamine (PA) solution significantly reduces not only acceptor-defect density but also intrinsic doping level, leading to dramatically enlarged depletion width of metal/polymer Schottky junctions, as confirmed by ultraviolet photoelectron spectroscopy and Mott-Schottky junction analyses. As a result, whole penetration regions of photons corresponding to absorption bands of P3HT can be fully covered by the depletion region of Schottky junctions, even without the assistance of external electric fields. In addition, it is shown that non-solvent exposure effects of PA dedoping further enable lower paracrystalline disorder and, thus, higher charge carrier mobility, by means of grazing incidence X-ray diffraction, field-effect mobility, and space-charge-limited current analyses. As a result of such synergetic advantages of the PA dedoping method, non-power-driven green-selective OPDs were demonstrated with a high specific detectivity exceeding 6 × 10 12 Jones and a low noise-equivalent power of 5.05 × 10 -14 W Hz -0.5 . Together with a fast temporal response of 26.9 μs and a wide linear dynamic range of 201 dB, the possibility of realizing non-power-driven, near-ideal optimization of solution-processed OPDs with a facile dedoping method is demonstrated.

Organic photodiodes (OPDs), based on organic semiconductors with high absorption coefficients for visible light, are emerging as potential candidates for replacing silicon photodiodes in image sensors, particularly due to the possibility of realizing a thin thickness and exclusion of color filters, both of which can contribute to a dramatically enhanced degree of integration for image sensors. Despite years of research, techniques have not yet been developed that allow the OPD itself to have color selectivity while maintaining a thin (<1 μm) OPD thickness, in combination with a sufficiently high detectivity (>10 12 cm·Hz 0.5 /W). To solve this issue, we introduce a concept of "etalon-electrode", which can perform the function of electrode and simultaneously the function of selective wavelength transparency. A strategically designed OPD architecture consisting of an etalon-electrode, a panchromatic organic active layer, and a counter electrode displays well-defined narrowband R-/G-/B-selective detectivity spectra depending on precision-adjusted thickness composition of the etalon-electrode. While a thin thickness of OPD is preserved at less than 800 nm including electrodes, active layer, and other buffer layers for all R-/G-/B-selective OPDs, high average detectivity values over 10 12 cm·Hz 0.5 /W are demonstrated. Furthermore, the characteristic of imparting color selectivity by the etalon-electrode enables a more facile full color patterning, such that a prototype of a 10 × 10 image sensor with a pixel pitch of 500 μm is realized, resulting in accurate picturing of a well-defined full color image.

Here, we introduce a method of tuning the high-detectivity spectra of the organic photodiode (OPD) to fabricate a thin-film filter-less full-color image sensor. The strategically introduced PIN junction enables a selective activation of excitons generated from the photons with low extinction coefficient in the active layer such that the separated holes/electrons can contribute to the external current. In addition, we show that a well-defined PIN junction blocks the injection of nonallowed charge carriers, leading to very low dark current and near-ideal diode characteristics. Consequently, the high specific detectivity over 1.0 × 10 12 Jones are observed from R/G/B-selective thin-film OPDs.

A thin film planar heterojunction organic photodetector (PHJ-OPD) is demonstrated. Different from a conventional sensitizer-doped photodetector, the limited spatial distribution of sensitizer in a PHJ-OPD enables significantly reduced thickness of the active layer without allowing the formation of unnecessary trap sites and electron percolation pathways. As a result, peak external quantum efficiency (EQE) of 120 700% and detectivity over 10 13 Jones are demonstrated with thin active layer thickness of 150 nm, which can be a significant benefit for high-resolution image sensor application. Furthermore, the operating voltage can be decreased to -5 V while maintaining high detectivity over 10 12 Jones. Remarkable thermal stability is also observed with minor change in detectivity for 2 h of continuous operation at 60 °C due to morphological robustness of PHJ. This work opens up a possibility of using a thin film PHJ-OPD as a key unit of high-resolution image sensor.

A push-pull-type donor copolymer, named PP-TPD, was synthesized with the Suzuki coupling reaction using 6H-phenanthro[1,10,9,8-cdefg]carbazole (PCZ) as the donor unit and 1,3-bis(5-bromothiophen-2-yl)-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione (TPD) as the acceptor unit. The synthesized PP-TPD was systematically investigated in terms of crystallinity and thermal, electrical, electrochemical, and optical properties. PP-TPD revealed green-selective absorption with a narrow full width at half-maximum of 138 nm. Green-selective organic photodiodes (OPDs) were constructed using PP-TPD as the green-absorbing donor and ZnO as the nonabsorbing acceptor material. The fabricated OPDs exhibited an extremely low dark current of 0.68 nA/cm 2 at -5 V and a high detectivity above 10 12 Jones at 550 nm. Moreover, they showed a sufficiently high 3-dB frequency and a linear dynamic range, similar to those of ideal-operating OPDs. The origin and physics background of the observed low dark current and high detectivity are discussed in detail.

We prepared a series of small molecules based on 7,7'-(4,4-bis(2-ethylhexyl)-4 H -silolo[3,2- b :4,5- b ']dithiophene-2,6-diyl)bis(4-(5'-hexyl-[2,2'-bithiophene]-5-yl)benzo[ c ][1,2,5]thiadiazole) with different fluorine substitution patterns ( 0F-4F ). Depending on symmetricity and numbers of fluorine atoms incorporated in the benzo[ c ][1,2,5]thiadiazole unit, they show very different optical and morphological properties in a film. 2F and 4F , which featured symmetric and even-numbered fluorine substitution patterns, display improved molecular packing structures and higher crystalline properties in a film compared with 1F and 3F and thus, 2F achieved the highest OTFT mobility, which is followed by 4F . In the bulk heterojunction solar cell fabricated with PC 71 BM, 2F achieves the highest photovoltaic performance with an 8.14% efficiency and 0F shows the lowest efficiency of 1.28%. Moreover, the planar-type perovskite solar cell (PSC) prepared with 2F as a dopant-free hole transport material shows a high power conversion efficiency of 14.5% due to its high charge transporting properties, which were significantly improved compared with the corresponding PSC device obtained from 0F (8.5%). From the studies, it is demonstrated that low variation in the local dipole moment and the narrow distribution of 2F conformers make intermolecular interactions favorable, which may effectively drive crystal formations in the solid state and thus, higher charge transport properties compared with 1F and 3F .

In this study, the strategy of using an organic-inorganic hybrid planar heterojunction consisting of polymeric semiconductors and inorganic nanocrystals is introduced to realize a high-performance hybrid photodiode (HPD) with low dark current and high detectivity. To prevent undesired charge injection under the reverse bias condition, which is the major dark current source of the photodiode, a well-defined planar heterojunction is strategically constructed via smart solution process techniques. The optimized HPD renders a low dark current of ∼10(-5) mA cm(-2) at -5 V and ∼10(-6) mA cm(-2) at -1 V, as well as a high detectivity ∼10(12) Jones across the entire visible wavelength range. Furthermore, excellent photocurrent stability is demonstrated under continuous light exposure. We believe that the solution-processed planar heterojunction with inverted structure can be an attractive alternative diode structure for fabricating high-performance HPDs, which usually suffer from high dark current issues.