02718nas a2200265 4500008004100000022001400041245008000055210006900135260000800204300001400212490000600226520192400232653001502156653001102171653001902182653001602201653001602217653001402233100001902247700001902266700001802285700001902303700001902322856011102341 2021 eng d a2574-097000aCrack-free conjugated PbS quantum dot-hole transport layers for solar cells0 aCrackfree conjugated PbS quantum dothole transport layers for so cAPR a4016-40250 v43 a

Colloidal quantum dots (QDs) benefit from solution-phase processing and band-gap tuning for their application in solar cell development. Today's QD solar cells rely on solid-state ligand exchange (SLE) to replace bulky oleic acid (OA) ligands with small 1,2-ethanedithiol (EDT) ligands to develop a conducting hole transport layer (HTL). High volume contraction in EDT conjugated QD films, however, leads to crack and porosity in the HTL, which is a major cause of concern for the device reproducibility and large-area solar cell development. We show that partial removal of the OA ligands in the solution phase reduces the volume contraction in solid films, thereby allowing the growth of crack-free QD films in the SLE process. The cleaning of QDs by repeated precipitation and redispersion using a protic methanol (MeOH) solvent helps with partial removal of the OA ligands, but it is detrimental to the electronic properties of QDs. We develop a one-step solution-phase partial ligand-exchange process using ammonium salts, which enable partial replacement of the OA ligands and passivation of the QD surface. Introduction of the facile partial ligand-exchange process eliminates the need for tedious and wasteful multiple cleaning steps with MeOH, while improving the photophysical properties of QDs. The advancement in QD processing helps to build crack-free, smooth, and conjugated QD films for their deployment as HTLs in solar cell development. Partial ligand exchange with NH4SCN leads to a 1.5 times increase in p doping and mobility over multiple MeOH-cleaned PbS QD films. HTLs developed using NH4SCN QDs show an improved photovoltaic performance to attain a 10.5% power conversion efficiency. Improvement in the depletion width and hole collection efficiency leads to a superior photovoltaic performance, as confirmed from experimental studies and one-dimensional solar cell capacitance simulation.

10aEfficiency10aligand10apolydispersity10aquantum dot10asolar cells10athin film1 aSharma, Ashish1 aDambhare, Neha1 aBera, Jayanta1 aSahu, Satyajit1 aRath, Arup, K. uhttps://library.ncl.res.in/content/crack-free-conjugated-pbs-quantum-dot-hole-transport-layers-solar-cells02092nas a2200253 4500008004100000245007200041210006900113260000800182300001400190490000600204520132000210653002101530653001401551653002401565653001601589653001701605100001801622700001701640700001901657700001801676700002201694700001901716856010301735 2022 eng d00aCdSe quantum dot-based nanocomposites for ultralow-power memristors0 aCdSe quantum dotbased nanocomposites for ultralowpower memristor cJUN a8502-85100 v53 a

The explosion in digital communication with the huge amount of data and the internet of things (IoT) led to the increasing demand for data storage technology with faster operation speed, high-density stacking, nonvolatility, and low power consumption for saving energy. Metal chalcogenide-based quantum dots (QDs) show excellent nonvolatile resistive memory behavior owing to their tunable electronic states and control in trap states by passivating the surface with different ligands. Here, we synthesized high-quality colloidal monodispersed CdSe QDs by the hot injection method. The CdSe QDs were blended with an organic polymer, poly(4-vinylpyridine) (PVP), to fabricate an Al\textbackslashCdSe-PVP\textbackslashAl device. Our device shows excellent bipolar nonvolatile resistive random access memory (RRAM) switching behavior with a high current ON/OFF ratio (I-ON/OFF) of 6.1 x 10(4), and it consumes ultralow power. The charge trapping and detrapping in the potential well formed by the CdSe QD and PVP combination result in resistive switching. This CdSe-PVP-based resistive random access memory (RRAM) device with a high I-ON/OFF, ultrafast switching speed, high endurance, low operating voltage, and long retention period can be used as a high-performance and ultralow-power memristive device.

10amemory switching10amemristor10ametal chalcogenides10anonvolatile10aquantum dots1 aBera, Jayanta1 aBetal, Atanu1 aSharma, Ashish1 aShankar, Uday1 aRath, Arup, Kumar1 aSahu, Satyajit uhttps://library.ncl.res.in/content/cdse-quantum-dot-based-nanocomposites-ultralow-power-memristors02185nas a2200193 4500008004100000022001400041245012500055210006900180260000800249300001100257490000800268520149100276100001801767700001701785700001901802700002201821700001901843856012901862 2022 eng d a0003-695100aColloidal MoS2 quantum dots for high-performance low power resistive memory devices with excellent temperature stability0 aColloidal MoS2 quantum dots for highperformance low power resist cJUN a2535020 v1203 a

Conventional memory technologies are facing enormous problems with downscaling, and are hence unable to fulfill the requirement of big data storage generated by a huge explosion of digital information. A resistive random access memory device (RRAM) is one of the most emerging technologies for next-generation computing data storage owing to its high-density stacking, ultrafast switching speed, high non-volatility, multilevel data storage, low power consumption, and simple device structure. In this work, colloidal MoS2 quantum dots (QDs) embedded in an insulating matrix of poly-(4vinylpyridine) (PVP) were used as an active layer to fabricate a RRAM device. The MoS2 QDs-PVP based RRAM device reveals an excellent nonvolatile resistive switching (RS) behavior with a maximum current on-off ratio (I-ON/I-OFF) of 10(5). High endurance, long retention time, and successive ``write-read-erase-read'' cycles indicate high-performance RRAM characteristics. The ultimate power consumption by this RRAM device is considerably low for energy saving. In addition, the MoS2 QDs-PVP based device shows RS behavior even at 130 degrees C. High I-ON/I-OFF, low operating power, high endurance, long retention time, and excellent stability with temperatures reveal that the MoS2 QDs-PVP based device can be a promising candidate for high-performance low power RRAM devices that can be operated at relatively higher temperatures. Published under an exclusive license by AIP Publishing.

1 aBera, Jayanta1 aBetal, Atanu1 aSharma, Ashish1 aRath, Arup, Kumar1 aSahu, Satyajit uhttps://library.ncl.res.in/content/colloidal-mos2-quantum-dots-high-performance-low-power-resistive-memory-devices-excellent02048nas a2200241 4500008004100000245009300041210006900134260000900203300001400212490000600226520128400232653002301516653001201539653001901551653001701570653001401587100001701601700001801618700001901636700001901655700001901674856011301693 2022 eng d00aComposition and surface morphology invariant high on-off ratio from an organic memristor0 aComposition and surface morphology invariant high onoff ratio fr cMAR  a1109-11160 v43 a

Material composition plays a crucial role in the device performance; thus, nonvolatile memory devices from a small molecule named 5-mercapto-1-methyl tetrazole (MMT) in an insulating polymer matrix of poly(4-vinyl pyridine) (PVP) were fabricated. The composition of the active material in the device was varied to observe its influence on the device's electronic properties. The device with a more or less weight ratio of MMT has a much smoother surface morphology, whereas when the contributions of MMT and PVP were equal, the average surface roughness increased. However, the maximum on-off current ratio for all the devices is 10(5), suggesting that the MMT molecule does not show any change in its characteristic properties when surrounded by an insulating material. When the device was fabricated without the polymer matrix, the surface morphology of the device completely changed as it was filled with large holes. These holes provide short-circuited pathways for the current by forming the direct metal contact between the top and bottom electrodes. The carrier transport through these devices follows various conduction mechanisms. Some of the dominating conduction mechanisms are direct tunneling and trap-free and trap-assisted space-charge-limited conduction.

10aNonvolatile memory10aPolymer10asmall molecule10aspace-charge10atunneling1 aBetal, Atanu1 aBera, Jayanta1 aSharma, Ashish1 aRath, Arup, K.1 aSahu, Satyajit uhttps://library.ncl.res.in/content/composition-and-surface-morphology-invariant-high-ratio-organic-memristor01746nas a2200193 4500008004100000022001400041245010000055210006900155260000900224300001400233490000700247520107400254100001701328700001801345700001901363700002201382700001901404856012901423 2023 eng d a1463-907600aCharge trapped CdS quantum dot embedded polymer matrix for a high speed and low power memristor0 aCharge trapped CdS quantum dot embedded polymer matrix for a hig cFEB  a3737-37440 v253 a

The data storage requirement in the digital world is increasing day by day with the advancement of the internet of things. In this respect, nonvolatile resistive random-access memory is an option that provides high density and low power data storage capabilities. In this work, zero-dimensional colloidal CdS quantum dots and a polymer composite at an appropriate ratio were used to fabricate a memristive device. Comparison with a pristine CdS quantum dot-based device reveals that a surrounding matrix around the quantum dots is needed for observing memristive behavior. The quantum dots embedded in the polymer matrix device showed extremely stable electrical switching behavior that can be operated for more than 300 cycles and 60 000 seconds. Moreover, the device needs extremely low power to operate at a very high speed. The smooth surface morphology dictates a charge trapping mechanism for the switching phenomenon; however, an interplay between different charge transport mechanisms leads to the fast switching and high on-off ratio of the device.

1 aBetal, Atanu1 aBera, Jayanta1 aSharma, Ashish1 aRath, Arup, K. K.1 aSahu, Satyajit uhttps://library.ncl.res.in/content/charge-trapped-cds-quantum-dot-embedded-polymer-matrix-high-speed-and-low-power-memristor02631nas a2200289 4500008004100000245014600041210006900187260000800256300001400264490000600278520164500284653001801929653001801947653002701965653001701992653002402009653003402033653000802067100001702075700001902092700001802111700002302129700001902152700001902171700001902190856013202209 2024 eng d00aScanning tunneling microscopy investigation of synaptic behavior in AgInS2 quantum dots: effect of ion transport in neuromorphic applications0 aScanning tunneling microscopy investigation of synaptic behavior cMAR a7226-72360 v73 a

Scanning tunneling microscopy (STM) is a powerful technique for investigating the nanoscale properties of functional materials. Additionally, scanning tunneling spectroscopy (STS) facilitates the determination of the local density of states (LDOS) within the material. In this study, we present an exploration of the resistive switching (RS) properties and neuromorphic computing capabilities of individual AgInS2 quantum dots, utilizing STM and STS techniques. By examining the material's bandgap and its temperature dependence, we uncover a nonlinear variation below the Debye temperature and a linear trend at higher temperatures. Moreover, STS measurements demonstrate changes in the conducting states induced by localized pulses, further confirming the unique characteristics of the quantum dots. The experimental devices constructed by using these quantum dots effectively replicate the RS properties observed at the nanoscale. To assess the neuromorphic application of the devices, pulse transient measurements simulating the learning and forgetting processes were conducted. The gradual set and reset processes successfully mimic the information retention and erasure capabilities essential for neuromorphic computing. Notably, the resistive switching mechanism in these devices is attributed to localized ionic transport, which highlights the significant involvement of ionic species in the observed RS behavior. The outcomes of this study contribute to the fundamental understanding of RS properties in single AgInS2 quantum dots and offer valuable insights into their potential applications in neuromorphic computing.

10acorona poling10aIon transport10aneuromorphic computing10aquantum dots10aresistive switching10aScanning tunneling microscopy10aSTS1 aBetal, Atanu1 aChetia, Anupam1 aBera, Jayanta1 aSaikia, Dibyajyoti1 aSharma, Ashish1 aRath, Arup, K.1 aSahu, Satyajit uhttps://library.ncl.res.in/content/scanning-tunneling-microscopy-investigation-synaptic-behavior-agins2-quantum-dots-effect-ion