Low-temperature Fabrication Research Articles

Recent progress of inverted organic-inorganic halide perovskite solar cells

In recent years, inverted perovskite solar cells (IPSCs) have attracted significant attention due to their low-temperature and cost-effective fabrication processes, hysteresis-free properties, excellent stability, and wide application. The efficiency gap between IPSCs and regular structures has shrunk to less than 1%. Over the past few years, IPSC research has mainly focused on optimizing power conversion efficiency to accelerate the development of IPSCs. This review provides an overview of recent improvements in the efficiency of IPSCs, including interface engineering and novel film production techniques to overcome critical obstacles. Tandem and integrated applications of IPSCs are also summarized. Furthermore, prospects for further development of IPSCs are discussed, including the development of new materials, methods, and device structures for novel IPSCs to meet the requirements of commercialization.

Modeling the path to >30% power conversion efficiency in perovskite solar cells with plasmonic nanoparticles.

Mixed organic-inorganic halide perovskite solar cells (PSCs) are a promising technology with increasing power conversion efficiency (PCE), low-cost material constituents, simple scalability, and a low-temperature solution fabrication process. Recent developments have seen energy conversion efficiencies increase from 3.8% to over 20%. However, to further improve PCE and reach the target efficiency of over 30%, light absorption through plasmonic nanostructures is a promising approach. In this work, we present a thorough quantitative analysis of the absorption spectrum of a methylammonium lead iodide (CH3NH3PbI3) perovskite solar cell using a nanoparticle (NP) array. Our multiphysics simulations using finite element methods (FEM) show that an array of Au nanospheres can increase average absorption >45%, compared to only 27.08% for the baseline structure without any NPs. Furthermore, we investigate the combined effect of engineered enhanced absorption on electrical and optical solar cell performance parameters using the one-dimensional solar cell capacitance software (SCAPS 1-D), which shows a PCE of ∼30.4%, significantly higher than the PCE of ∼21% for cells without NPs. Our findings demonstrate the potential of plasmonic perovskite research for next-generation optoelectronic technologies.

Perovskite materials for photovoltaics: a review

Photovoltaic is among the most propitious renewable energy sources for meeting global energy demands. Owing to their simple solution synthesis procedure, lightweight, wearable, power conversion efficiency, flyable, ready to deploy for extremist lightweight space, and reduced cost of constituent materials, perovskite solar cells have gotten huge interest in the past years. Because of the high-quality perovskite film attained by low-temperature fabrication methods, as well as the development of appropriate interface and electrode materials, the effectiveness of perovskite solar cells (PSCs) has topped 25% efficiency in recent years. Furthermore, perovskite solar cells' stabilization has gotten a lot of well-deserved recognition. The future of various carbon, tin, and polymer materials-based perovskite solar cells has even been explored, as well as their industrial expansion possibility are also discussed. This review paper summarizes important accomplishments to date, highlights the unique properties of these perovskites that have led to their fast upsurge, and highlights the problems that must be overcome for perovskite solar cells to be developed and commercialized successfully.

Microwave plasma-assisted reactive HiPIMS of InN films: Plasma environment and material characterisation

This work focuses on the low temperature fabrication process of InN thin films via microwave plasma-assisted reactive high power impulse magnetron sputtering (MAR-HiPIMS). The influence of microwave plasma on the HiPIMS discharge process at various nitrogen flows and microwave powers was monitored and characterised through in situ diagnostics, including following HiPIMS I(V,t) curves, optical emission spectroscopy (OES), as well as performing time-resolved Langmuir probe and time-of-flight mass spectroscopy (ToF-MS) measurements. This was followed by the deposition of InN films via standard reactive HiPIMS (reference sample) and MAR-HiPIMS and their characterisation via X-ray diffraction (XRD), reflectometry (XRR), as well as scanning and transmission electron microscopy (SEM, TEM). It was found that the microwave plasma facilitates the dissociation/activation of nitrogen species and supplies seed electrons to the magnetron discharge plasma. Furthermore, the energy of the incoming ions was determined via ToF-MS, and it was possible to identify their plasma origin and temporal behaviour. The produced R-HiPIMS sample was highly metallic, with no nitride phase detected. The MAR-HiPMS film, however, was stoichiometric and exhibited (0002) direction texturing, with an optical bandgap of approx. 1.5 eV, electron concentration of 2.72 × 1020 cm−3 and electron mobility of 7.16 cm2V−1 s−1 (in the range for polycrystalline InN).

Rapid microwave-assisted synthesis and magnetic properties of high-entropy spinel (Cr0.2Mn0.2Fe0.2Co0.2-xNi0.2Znx)3O4 nanoparticles

High-entropy oxide (HEO) has recently become popular because of its unique multifunctional performance. In this study, we developed a novel microwave-assisted method for the production of HEO nanoparticles with the composition (Cr0.2Fe0.2Mn0.2Co0.2-xNi0.2Znx)3O4 (x = 0, 0.05, 0.1, and 0.2). The results revealed that all metallic elements were uniformly distributed throughout the single-phase cubic spinel structure of the HEO nanoparticles. The particle size distributions of four fabricated samples ranged from 10 to 50 nm. Because of its numerous advantages such as the ultrafast and low-temperature fabrication of nanoscale and high-purity products at a relatively low cost, the suggested methodology is an excellent synthesis method. The original HEO spinel (x = 0) achieved saturated magnetization (Ms) and coercivity (Hc) values of 24.3 emu/g and 160 Oe, respectively, at room temperature. Zinc substitution in the HEO composition indicated that Ms and Hc decreased with increasing zinc concentration owing to its non-magnetic nature.

Cost-effective and self-reducible Cu-Ni composite ink for low temperature fabrication of highly conductive and anti-oxidative electrodes

• The inexpensive and self-reducing Cu-Ni composite ink was prepared. • The high quality printed Cu-Ni electrodes were fabricated at 180°C. • The Cu-Ni electrodes presented good conductivity and thermal stability. In this work, an inexpensive and self-reducible Cu-Ni composite ink was designed for low temperature fabrication of the highly conductive and anti-oxidative Cu-Ni electrodes. The Cu-Ni electrode was obtained at a lower sintering temperature originating from the self-catalyzed characteristic of Cu micron particles. Consequently, the Cu-Ni electrode sintered at 180 °C exhibits high conductivity with a low electrical resistivity of 7.1×10 -5 Ω.cm. and its relative resistance is significantly lower than that of Cu electrode after the high temperature aging test. These results indicate that the self-reducible Cu-Ni composite ink provides a promising prospect for the highly conductive and stable electrode.

Low-temperature fabrication and properties of porous calcium hexaluminate (CA6) ceramics with low thermal conductivity by one-step method

In this study, one-step molten salt method followed by low-temperature sintering is employed for fabricating porous calcium hexaluminate (CA6) ceramics with ideal plate-like structure and low thermal conductivity via the assistance of CaCl2. The porous CA6 ceramic containing 15 wt% CaCl2 sintered at 1400 °C for 3 h exhibits desirable compressive strength (7.14 MPa), low bulk density (1.47 g/cm3), high porosity (61.12%), and low conductivity (0.439 W/(m·K)). The results imply that CaCl2, as a pore-forming agent and an additional source of CaO, provides a large number of liquid phases and resulting in quantities of closed pores. Moreover, the reactions between molten Al2O3 and CaCl2 alter the mass transfer modes of Al2O3 and accelerate its phase transition to α-Al2O3 in addition to contributing to the conversion of CaCl2 to CaO and the subsequent formation of CA6, which results in the entire synthesis of low-temperature CA6 at around 1400 °C. Therefore, there is no need for extra salt washing treatment owing to the consumption and evaporation of CaCl2, which makes this one-step molten salt method much more advantageous in terms of its economical and highly efficient.

Effect of carbon and oxygen on the high-temperature properties of silicon carbide–hafnium carbide nanocomposite fiber

The polymer-derived ceramics (PDCs) technique enables relatively low-temperature fabrication of Si-based ceramics, with silicon carbide fiber as a representative product. Polycarbosilane (PCS) has Si-C backbone structures and can be converted to silicon carbide. In the PDCs method, residual or excess carbon is generated from the precursor (C/Si ratio = 2 for polycarbosilane). Because of the non-stoichiometry of SiC, the physicochemical properties of polymer-derived SiC are inferior to those of conventional monolithic SiC. Herein, a silicon carbide-hafnium carbide nanocomposite fiber was optimized by crosslinking oxygen into the PCS fiber by regulating the oxidation curing time. During pyrolysis, carbothermal reduction, and sintering, carbon was removed by reaction with hydrogen and cross-linked oxygen. Non-destructive techniques (X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and high-temperature thermomechanical analysis) were used to investigate the effects of excess carbon. The microstructure of the near-stoichiometric SiC-HfC nanocomposite fiber was more densified, with superior high-temperature properties.

Low-temperature fabrication of high-performance AlN/Ag/AlN thin films for transparent electrode applications

Low-temperature fabrication of high-performance AlN/Ag/AlN thin films for transparent electrode applications

Low-Temperature Fabrication of TiC Nanotube Arrays by Molten Salt Electrolysis for Supercapacitor Application

A strategy for the synthesis of nanostructured metal carbides that can convert oxides into carbides while maintaining their original nanomorphology is proposed in this study. TiC nanotube arrays (TiC NTAs) were successfully prepared by electrodeoxidation and carbonization in a low-temperature molten salt (600 °C) using TiO2 nanotube arrays (TiO2 NTAs) as precursors. The effects of different factors on the heritability of nanostructures are discussed in detail. TiC NTAs have a highly ordered and directional array structure, a large specific surface area, excellent electrical conductivity, and outstanding chemical stability. Quasi-solid-state supercapacitors based on TiC NTA electrodes exhibit excellent electrochemical energy storage properties such as low charge transfer resistance, high energy density (4.2 μW h cm–2), and excellent cycle stability (90% retention after 10,000 cycles). This study demonstrates a high-performance supercapacitor nanoarray material and provides a general method to synthesize nanostructured metal carbides.

Novel Ultrafast Lu2O3:Yb Ceramics for Future HEP Applications

Inorganic scintillators activated by charge transfer luminescence Yb3+ are considered promising ultrafast material to break the ps timing barrier for future high energy physics applications. Inorganic scintillators in ceramic form are potentially more cost-effective than crystals because of their lower fabrication temperature and no need for aftergrowth mechanical processing. This paper reports an investigation on Lu2O3:Yb and Lu2xY2(1−x)O3:Yb scintillating ceramic samples fabricated by Radiation Monitoring Devices Inc. All samples show X-ray excited luminescence peaked at 370 nm. Ultrafast decay time of 1.1 ns was observed by using a microchannel plate-photomultiplier tube-based test bench at Caltech. Considering its intrinsic high density (9.4 g/cm3), Lu2O3:Yb ceramics are promising for future time of fight application for high energy physics experiments.

Low temperature, area-selective atomic layer deposition of NiO and Ni

Nickel and nickel oxide are utilized within various device heterostructures for chemical sensing, solar cells, batteries, etc. Recently, the rising interest in realizing low-cost, flexible electronics to enable ubiquitous sensors and solar panels, next-generation displays, and improved human-machine interfaces has driven interest in the development of low-temperature fabrication processes for the integration of inorganic devices with polymeric substrates. Here, we report the low-temperature area-selective atomic layer deposition of Ni by reduction of preformed NiO. Area-selective deposition of NiO is performed at 100 °C using bis(N,N'-di-tert-butylacetamidinato) nickel(II) and water on SiO2 and polystyrene. NiO grows two-dimensionally and without nucleation delay on oxide substrates but not on SiNx or polystyrene, which require surface treatments to promote NiO nucleation. Additionally, prepatterned sp2 carbon-rich resists inhibit the nucleation of NiO, and in this way, carbon-free NiO may be patterned. Subsequent thermal reduction of NiO to Ni was investigated using H2 (50–80 m Torr) and thermally generated H-atoms (3 × 10−5 Torr chamber pressure). Due to the relatively high free surface energy of Ni metal, Ni films undergo dewetting at elevated temperatures when solid-state transport is enabled. Reduction of NiO to Ni is demonstrated at 100 °C and below using atomic hydrogen. In situ x-ray photoelectron spectroscopy is used to determine oxidation state and ex situ x-ray reflectivity and atomic force microscopy are used to probe the film thickness and surface morphology, respectively.

Performance Enhancement of Solution-Processed SixSnyO TFTs using Solution Combustion Synthesis

Amorphous oxide semiconductors thin-film transistors (AOs TFTs) have gained interest over the years because of their advantages over a-Si and poly-Si transistors.In particular, tin oxide is used as a semiconductor material because of its abundance, low toxicity, and high intrinsic mobility. Performance-wise, tin oxide TFTs need improvement because the reported average mobility remains < 10 cm2/Vs.1 Previous research used silicon doping to reduce tin oxide’s oxygen vacancies and improve its performance as a semiconductor channel.Currently, SixSnyO TFTs are fabricated using vacuum process, but solution processing is important to realize large-scale and high-throughput electronics. Sol-gel method is one of the conventional routes to produce solution-processed metal oxides. However, it requires high temperature (≤500°C) to facilitate film densification which is not compatible with flexible substrates having low degradation temperatures. Among the approaches for low-temperature TFT fabrication, solution combustion synthesis (SCS) has garnered significant attention because of its simplicity and versatility.2 SCS uses the energy released by combustion to help the formation of more M-O-M networks in the film. Thus, there is no need to use high temperature to condense and densify the film. This study attempts to produce SixSnyO TFTs through solution processing for the first time. We investigated the effect of solution combustion synthesis to the quality of SixSnyO films. Next, we optimized the aging time and oxidizer to fuel ratio (ammonium nitrate to urea) to determine the films with better quality. For aging time optimization, SixSnyO precursors were stirred at RT for 24-h, 48-h, and 72-h. Lastly, we compared the TFT performance in terms transfer characteristics of SixSnyO TFTs fabricated by sol-gel and SCS annealed at the same temperature. Secondary ion mass spectrometry (SIMS) analysis was used to compare the carbon impurities present in both SixSnyO films. The sol-gel film contained higher amounts of carbon impurities, about an order of magnitude higher as shown in Figure 1. This proves that SCS provides extra energy to help degrade the carbon-containing compounds in the film. Carbon atoms are considered impurities that can introduce defects in the SixSnyO film. These defects are detrimental to the performance characteristics of the fabricated TFT device. In addition, the thickness of the films was determined using X-ray reflectivity. The SCS film is 15.70 nm-thick while the sol-gel film is 18.88-nm thick. Furthermore, optimization of the SixSnyO films via SCS revealed that oxidizer to fuel ratio affects the roughness and amount of M-O bonds formed in the film. The 3:1 ratio failed to produce a film while other ratios were successful in producing films. Although the film with 1:1 ratio has root mean square roughness (Rq) value of 0.380 nm, it contains depressions and voids. On the other hand, the film using a 1:3 ratio showed a uniform and even surface with Rq value of 0.377 nm. In addition, characterization of the two films through X-ray photoelectron spectroscopy (XPS) showed higher percentage of M-O bonds in the O1s spectrum (530.5 eV) for the film with 1:3 ratio. The values are 45.9% and 59.3% for 1:1 and 1:3 ratios, respectively. The amount of oxygen vacancy and H- containing compounds also decreased in the 1:3 film.SixSnyO TFTs were fabricated from both SCS and sol-gel methods. Both TFTs showed high off-current and highly negative Vth, as shown in Figure 1. Therefore, both TFTs still contain several defects which suggests that 3% Si doping may be insufficient and must be increased to produce a significant effect. The sol-gel fabricated TFT also showed lower drain current. Therefore, the low annealing temperature at 300 ˚C is insufficient to densify the film and reduce impurities. On the other hand, SCS-assisted fabrication showed higher mobility at 3.14 cm2/Vs – confirming that SCS provided additional energy to degrade impurities and improve the M-O network in the SixSnyO channel. In conclusion, we were able to produce SixSnyO TFTs with improved mobility using solution combustion synthesis. However, the high V th and high off-current issues need to be addressed by increasing silicon dopant addition and exploring other fuel options. But overall, we can confirm that SCS is beneficial in improving the quality of SixSnyO films annealed at 300 ˚C. In the future, this low temperature fabrication is important to realize flexible SixSnyO TFT devices.AcknowledgementsThis research was supported by NAIST foundation grant.References Chang, H., et al. ACS Applied Electronic Materials, 3(11), 4943–4949.Carlos, E., et al. Chemistry - A European Journal, 26(42), 9099–9125. Figure 1

(Digital Presentation) Low Dimensional Channel Materials for Logic Transistors

A key technology future direction is CMOS + X, where X can be memory, photonics, spintronics, power electronics, nanomechanics, sensors and actuators, RF/mm-wave, and even quantum computing. Nanosystems of 3D integrated “X” technology (N3XT) is a key concept at the chip level. We must also go beyond a single chip from a wafer and focus on integrating chips into systems using MOSAIC (MOnolithic Stacked Assembled IC). I will give an overview of the new materials and device technologies that may need to be developed to realize this vision. In particular, low-dimensional materials are suitable for logic transistors in this 3D MOSAIC of N3XT chips vision because of the low temperature for device fabrication as well as the thin device layers.

(Invited, Digital Presentation) Heterogeneous IGZO/Si CFET Monolithic 3D Integration

Monolithic 3D-IC is one of the solutions to relieve Moore’s law with vertically integrating circuits for sub-1nm technology nodes. Therefore, thin-film transistors (TFTs) play an important role in this trend because of their low fabrication temperature to realize back-end circuits. On the other hand, 3D integrating filter, duplexer, switch, and so on is necessary as antennas array requirements increase in 5G or beyond. Consequently, it is foreseeable to adopt TFTs to implement radio frequency (RF) devices. Fig. 1 shows the schematic ideal 3D SoC for sub-1nm technology. Our previous research tried to demonstrate high-frequency back-end devices based on the gate-all-around stacked nanosheet low-temperature polycrystalline silicon channel (GAA NS LTPS). Fig.2 shows the current-voltage transfer characteristics of different width designs of LTPS and α-IGZO devices. The only way to enhance GAA NS LTPS RF devices with the same process is by increasing channels. However, it leads to a larger footprint, and the frequency doesn’t boost with increasing channels in proportion because of the capacitance between the multiple channels. In the meantime, the LTPS gate controllability becomes poor, and threshold voltage shifts significantly when the drive current is improved by widening channel width. Consequently, a-IGZO is adopted as the channel material of RF devices to solve the problem mentioned above. The a-IGZO film is back-end compatible and has transparency and high uniformity. The most important is that the gate controllability decay phenomenon is negligible no matter what the channel width is, which is helpful for different width designs. In contrast, IGZO devices can keep their threshold voltage and have ultra-low leakage current due to a large bandgap. According to the system on panel (SoP) trend, we attempt to integrate RFIC with the peripheral circuit on a substrate. Therefore, a-IGZO is also introduced as a pull-down transistor in a CMOS for power reduction and process simplicity. To further minimize the footprint, the a-IGZO devices are nanoscale and stacked on the p-type LTPS as the defined heterogeneous CFET (HCFET), which is demonstrated in the previous study [1]. In this talk, we will discuss HCFET architecture in detail. We compared junctionless mode (JL) and inversion mode (IM) for bottom p-type LTPS in HCFET. In our results, IM is better than JL as the junction structure for bottom PMOS because the requirement of the bottom channel in a HCFET is thin and width flexible for design. In addition, a trench gate of the bottom device plays an important role in HCFET. The trench tri-gate structure can avoid gate dielectric damage by plasma in the etching process, keep the top IGZO layer continuously and enhance performance compared to the general tri-gate structure. On the other hand, the gate of top n-type IGZO can be bottom gate only or dual gate for different requirements. Finally, HCFET can significantly reduce the distance between IGZO and p-type LTPS channels to save power and lower latency in the circuit.[1] S. -W. Chang et al., "First Demonstration of Heterogeneous IGZO/Si CFET Monolithic 3-D Integration With Dual Work Function Gate for Ultralow-Power SRAM and RF Applications," in IEEE Transactions on Electron Devices, vol. 69, no. 4, pp. 2101-2107, April 2022, doi: 10.1109/TED.2021.3138947. Figure 1

Microwave-Assisted Annealing Method for Low-Temperature Fabrication of Amorphous Indium-Gallium-Zinc Oxide Thin-Film Transistors

Compared with conventional silicon-based semiconductors, amorphous oxide semiconductors present several advantages, including the possibility of room-temperature fabrication, excellent uniformity, high transmittance, and high electron mobility. Notably, the application of oxide semiconductors to flexible electronic devices requires a low-temperature fabrication process. However, for the realization of semiconductor characteristics and stable products, the fabrication process requires annealing at temperatures of 300 °C or higher. To address this, a low-temperature microwave annealing method, which improves the electrical characteristics of a transistor and reduces the production time compared with the conventional annealing method, is presented herein. Microwave annealing is a well-known method of annealing that minimizes the heat energy transferred to a substrate via instantaneous heat transfer through the vibrations of the lattice in the material during microwave irradiation and is suitable as a low-temperature annealing method. In this study, we evaluate the electrical characteristics of devices subjected to conventional annealing at 200 °C and 300 °C for 1 h and microwave annealing at 200 °C for 10 min. For the device subjected to microwave annealing at 200 °C for 10 min, the threshold voltage, current on/off ratio, subthreshold swing, and saturation mobility are 13.9 V, 1.14 × 105, 3.05 V/dec, and 4.23 cm2/V·s, respectively. These characteristic results are far superior to the characteristic results of the device subjected to conventional annealing at 200 °C for 1 h and are equivalent to those of the device treated at 300 °C for 1 h. Thus, this study develops a more effective annealing method, which facilitates low-temperature fabrication in a reduced period.

UV Ozone based rapid low temperature fabrication of flexible dye sensitized solar cells

Herein, we have developed a multilayer TiO2 film thickness of around 4 µm at lower temperature (120 °C) by spin coating and doctor blade technique on polyethylene terephthalate (ITO-PET) substrate. Further, the additional processing step Ultravoilet-Ozone (UVO3) treatment was performed on TiO2 electron transport layer (ETL) to enhance the performance of FDSSCs. UVO3 treatment significantly improved the crystallinity and charge transport characteristic of ETL by removing the organic impurities. The photovoltaic devices based on 4 h of UVO3 treated TiO2 film exhibited superior device performance with an overall power conversion efficiency (PCE) of 2.53% compared to 1.43% (without UVO3 treatment). Electrochemical impedance measurement indicated that TiO2 layer treated with UVO3 decreased series resistance, electron recombination and improved electron life substantially. The improved device properties, simple preparation procedure and low processing cost, enable this FDSSCs fabrication method to be a credible alternative of conventional techniques.

Low-temperature cross-linking fabrication of sub-nanoporous SiC-based membranes for application to the pervaporation removal of methanol

Separating azeotropic organic-organic mixtures using membranes is of great importance in the chemical and petrochemical industries, but remains extremely challenging because membranes must be able to withstand harsh working conditions while providing adequate permselectivity. Silicon carbide (SiC)-based membranes have attracted a great deal of interest due to their high level of structural stability, mechanical strength, and corrosion resistance. Herein is an account of the first study focused on a systematic investigation into the physicochemical and pore structural variations of polycarbosilane (PCS)-derived SiC-based membranes under different air-curing and pyrolysis temperatures. Air curing for cross-linking behavior was found to occur at temperatures as low as 150 °C, and the completion of polymer-to-ceramic conversion for PCS was observed at 750 °C. In addition, the pore structure and surface properties (hydrophilicity/hydrophobicity) of PCS membranes could be tuned by the pyrolysis temperature. PCS membranes derived from air curing at a temperature as low as 150 °C possessed sub-nanopores that ranged from 0.5 to 0.66 nm depending on the pyrolysis temperature. The formation of these sub-nanopores was attributed to sparsely cross-linked networks. Subsequently, the pervaporation (PV) performance of methanol/methyl acetate, methanol/toluene, and methanol/methyl tert-butyl ether were evaluated and discussed with respect to any effects of different pore sizes of the membranes and operating parameters. The most outstanding separation performance emerged from SiC-based membranes with a pore size of 0.50 nm that were air-cured at 150 °C and then pyrolyzed at 750 °C. The impressive PV separation capability was attributed to the surface hydrophilicity, suitable pore size, and high quality of the SiC-based membranes. Furthermore, the PV performance correlated well with single-gas permeation, suggesting that PV performance could be predicted based on single-gas permeation. The developed SiC-based membranes have excellent separation performance and are a promising candidate for the PV separation of MeOH from organic mixture systems.

An organic synaptic circuit: toward flexible and biocompatible organic neuromorphic processing

In the nervous system synapses play a critical role in computation. In neuromorphic systems, biologically inspired hardware implementations of spiking neural networks, electronic synaptic circuits pass signals between silicon neurons by integrating pre-synaptic voltage pulses and converting them into post-synaptic currents, which are scaled by the synaptic weight parameter. The overwhelming majority of neuromorphic systems are implemented using inorganic, mainly silicon, technology. As such, they are physically rigid, require expensive fabrication equipment and high fabrication temperatures, are limited to small-area fabrication, and are difficult to interface with biological tissue. Organic electronics are based on electronic properties of carbon-based molecules and polymers and offer benefits including physical flexibility, low cost, low temperature, and large-area fabrication, as well as biocompatibility, all unavailable to inorganic electronics. Here, we demonstrate an organic differential-pair integrator synaptic circuit, a biologically realistic synapse model, implemented using physically flexible complementary organic electronics. The synapse is shown to convert input voltage spikes into output current traces with biologically realistic time scales. We characterize circuit’s responses based on various synaptic parameters, including gain and weighting voltages, time-constant, synaptic capacitance, and circuit response due to inputs of different frequencies. Time constants comparable to those of biological synapses and the neurons are critical in processing real-world sensory signals such as speech, or bio-signals measured from the body. For processing even slower signals, e.g., on behavioral time scales, we demonstrate time constants in excess of two seconds, while biologically plausible time constants are achieved by deploying smaller synaptic capacitors. We measure the circuit synaptic response to input voltage spikes and present the circuit response properties using custom-made circuit simulations, which are in good agreement with the measured behavior.

Breakthroughs in Perovskite Solar Cells: Advancing Efficiency and Stability for Next-Generation Photovoltaics

Perovskite solar cells (PSCs) have emerged as a revolutionary technology in photovoltaics, demonstrating rapid progress and potential for transforming solar energy generation. This paper delves into the latest breakthroughs in PSCs, focusing on enhancing efficiency and stability for next-generation photovoltaics. We trace the evolution of PSCs from their inception in 2009, where initial power conversion efficiencies (PCEs) were 3.8%, to recent advancements surpassing 25%. Key advantages of PSCs, such as low-temperature solution-based fabrication and the potential for flexible, lightweight solar panels, are discussed. Our research is structured around five main objectives: first, investigating advances in perovskite materials, particularly mixed cations and anions that enhance efficiency and stability. Second, exploring strategies to boost efficiency through advanced light management, optimized charge transport layers, and improved interface engineering. Third, addressing stability by developing robust encapsulation techniques and moisture-resistant materials, alongside optimizing thermal and photostability. Fourth, assessing innovative device architectures like tandem solar cells and flexible, lightweight designs for diverse applications. Fifth, examining the scalability of PSC production, including manufacturing challenges, cost analysis, and market potential. By addressing these objectives, the paper provides a comprehensive overview of current PSC technology and identifies key areas for future development, aiming to advance PSCs as a viable, sustainable solution for global energy needs.