Average Mobility Research Articles

High-performance flexible organic field effect transistors with print-based nanowires

Polymer nanowire (NW) organic field-effect transistors (OFETs) integrated on highly aligned large-area flexible substrates are candidate structures for the development of high-performance flexible electronics. This work presents a universal technique, coaxial focused electrohydrodynamic jet (CFEJ) printing technology, to fabricate highly aligned 90-nm-diameter polymer arrays. This method allows for the preparation of uniformly shaped and precisely positioned nanowires directly on flexible substrates without transfer, thus ensuring their electrical properties. Using indacenodithiophene-co-benzothiadiazole (IDT-BT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8-BT) as example materials, 5 cm2 arrays were prepared with only minute size variations, which is extremely difficult to do using previously reported methods. According to 2D-GIXRD analysis, the molecules inside the nanowires mainly adopted face-on π-stacking crystallite arrangements. This is quite different from the mixed arrangement of thin films. Nanowire-based OFETs exhibited a high average hole mobility of 1.1 cm2 V−1 s−1 and good device uniformity, indicating the applicability of CFEJ printing as a potential batch manufacturing and integration process for high-performance, scalable polymer nanowire-based OFET circuits. This technique can be used to fabricate various polymer arrays, enabling the use of organic polymer semiconductors in large-area, high-performance electronic devices and providing a new path for the fabrication of flexible displays and wearable electronics in the future.

Shellac as dielectric materials in organic field-effect transistors: from silicon to paper substrates

Recent advances in the design and preparation of electroactive materials, particularly semiconducting and conductive polymers, have resulted in the creation of novel organic electronics with advanced functionality and performance competitive with that of devices made of silicon. With an increasing number of organic and printed electronics being engineered and produced at a larger scale, the environmental cost of the final organic electronic devices (life cycle, environmental impact, etc) needs to be considered. While e-waste is already a growing global problem, improving the sustainability of emerging electronics through a careful materials selection is highly desirable. In this work, we explore the use of shellac as a sustainable greener dielectric material in organic field-effect transistors. A careful examination of shellac in combination with diketopyrrolopyrrole-based semiconducting polymers was performed on rigid substrates through atomic force microscopy (AFM) and the fabrication of thin film transistors. All devices made from this green dielectric showed good performance and device characteristics. Building from this investigation, shellac was further integrated with paper substrates to fabricate paper-based thin film transistors. Thin film samples based on shellac on both silicon wafer and paper substrates were characterized by AFM to investigate solid-state morphology of shellac and selected semiconducting materials. Through careful optimization of the device architecture and processing time, device characteristics and performances on paper substrates (average charge mobilities and on/off current ratios) were comparable to those of devices prepared on silicon wafers, confirming that shellac, in combination with organic semiconducting polymers, can be an advantageous dielectric material to be used for the fabrication of greener and sustainable thin film electronics from renewable feedstocks and components.

Corona Poling Induced Phase Transition to Highly Polar Phase in P(VDF-TrFE-CFE) Dielectric and Charge Transport of Organic Field-Effect Transistors.

Increasing the number of charge carriers flowing through the charge transport channel to improve the electrical performance of organic field-effect transistors (OFETs) is important because it leads to a low driving voltage and a high drain current value. This paper proposes a new strategy, the corona poling process, to enhance the electrical performance of OFETs using an external electric field when forming a dielectric film using a PVDF-based high-k dielectric terpolymer, P(VDF-TrFE-CFE). A corona poling process was applied to align the dipoles with high-k dielectric molecules and improve the capacitance, thereby increasing the number of charge carriers. Through this process, by observing the phase transition of a PVDF dielectric through a corona poling process in the GIWAXS data, the phase transition through an external electric field was thoroughly revealed for the first time. As a result, the capacitance of high-k dielectric films can be improved, and the amount of charge carriers can be increased by a simple corona poling process. In addition, to reduce the effect of deep trap sites caused by the dipole alignment, a thin low-k dielectric, polystyrene (PS), was introduced between the active and high-k dielectric layers to provide trap site passivation, thereby increasing the electrical performance of the OFET. Therefore, through this strategy, using a diketopyrrolopyrrole (DPP)-based donor-acceptor (D-A) copolymer as an active material of OFET, the average saturation region hole mobility was improved from 0.34 to 0.60 cm2/Vs. Thus, the electrical performances of the OFETs were improved by enhancing the capacitance through the corona poling process and reducing the charge carrier trap sites introduced by the high-k and low-k bi-layer dielectric layer. Importantly, this work offers a new strategy for the post-treatment to improve electrical performance of organic devices.

Improving Charge Injection for Organic Field‐Effect Transistor Array via Chemical Functionalized Van der Waals Top‐Contacts

AbstractEfficient charge injection at metal/semiconductor interface is of great importance for high‐performance organic field‐effect transistors (OFETs). In OFETs, top‐contact configuration generally exhibits better injection efficiency but may induces thermal damage to organic layer and is intrinsically difficult to modified with chemisorbs at metal/semiconductor interface. Herein, a versatile, large‐scale and damage‐free metal integration strategy is reported to achieve efficient charge injection in OFETs by applying self‐assembly monolayers (SAMs) functionalized van der Waals (vdW) top‐contact electrodes. Centimeter scale metal electrodes are transferred onto organic single crystal to form OFETs array without residual left. vdW contact provides a clear and atomic sharp interface, and thus the inherent electronic structure and physical properties of the pristine heterostructure interface can be retained. Modifying fluorinated SAMs at metal/semiconductor interface alters the work function of Au by 350 meV, and thus reduces the energy barrier for charge injection. As a result, OFETs array exhibits excellent performance characteristics with an average mobility of 3.6 cm2 V−1 s−1, negligible hysteresis and a high on/off ratio above 106 on high‐k AlOx dielectric. Organic unipolar inverters based on all vdW contact are also demonstrated. This strategy paves the way for both fundamental study and practical applications of organic electronics.

Creating Adjusted Scores Targeting mobiLity Empowerment (CASTLE 1): determination of normative mobility scores after lower limb amputation for each year of adulthood

Purpose As United States healthcare transitions from traditional fee-for-service models to value-based care, there is increased need to demonstrate quality care through clinical outcomes. Therefore, the purpose of this study was to create equations to calculate an expected mobility score for lower limb prosthesis users specific to their age, etiology, and amputation level to provide benchmarks to qualify good outcomes. Materials and Methods A retrospective cross-sectional analysis of outcomes collected during clinical care was performed. Individuals were grouped based on amputation level (unilateral above-knee (AKA) or below-knee (BKA)) and etiology (trauma or diabetes/dysvascular (DV)). The mean mobility score (PLUS-M® T-score) for each year of age was calculated. AKAs were further stratified into having a microprocessor knee (MPK) or non-microprocessor (nMPK) for secondary analysis. Results As expected, average prosthetic mobility declined with age. Overall, BKAs had higher PLUS-M T-scores compared to AKAs and trauma etiologies had higher scores compared to DV. For AKAs, those with a MPK had higher T-scores compared to those with a nMPK. Conclusions Results from this study provide average mobility for adult patients across every year of life. This can be leveraged to create a mobility adjustment factor to qualify good outcomes in lower limb prosthetic care. IMPLICATIONS FOR REHABILITATION Normative values of mobility are needed to qualify good outcomes in prosthetic care as healthcare shifts towards value-based care. Understanding where an individual is relative to others with similar characteristics (e.g., age, etiology, gender, amputation level, and device type) can provide clinicians with better benchmarks for individual goal-setting. The ability to generate predicted mobility scores specific to each individual can create a mobility adjustment factor to better qualify good outcomes.

Aza-anthradithiophene-based conjugated polymers: Synthesis and field-effect transistor application

Acenedithiophenes are classical fused-ring units for constructing conjugated polymers. In this work, a new aza-anthradithiophene unit has been designed and was for the first time employed as building unit to constructing conjugated polymers for organic field-effect transistors. Two conjugated polymers based on thiophthene (P1) and benzothiadiazole (P2) as co-units were synthesized by Stille and Suzuki coupling reactions, respectively. The thermal stability, optical and electrochemical properties, and microstructure were investigated. Organic field-effect transistor devices based on conjugated polymers as semiconductor layer were also fabricated and two polymers exhibited typical hole transport characteristics with the average field-effect mobility up to 7.9 × 10−4 cm2V−1s−1 and Ion/Ioff ratios over 104.

Cross-regional analysis of the association between human mobility and COVID-19 infection in Southeast Asia during the transitional period of "living with COVID-19".

In response to COVID-19, Southeast Asian (SEA) countries had imposed stringent lockdowns and restrictions to mitigate the pandemic ever since 2019. Because of a gradually boosting vaccination rate along with a strong demand for economic recovery, many governments have shifted the intervention strategy from restrictions to "Living with COVID-19" where people gradually resumed their normal activities since the second half of the year 2021. Noticeably, timelines for enacting the loosened strategy varied across Southeast Asian countries, which resulted in different patterns of human mobility across space and time. This thus presents an opportunity to study the relationship between mobility and the number of infection cases across regions, which could provide support for ongoing interventions in terms of effectiveness. This study aimed to investigate the association between human mobility and COVID-19 infections across space and time during the transition period of shifting strategies from restrictions to normal living in Southeast Asia. Our research results have significant implications for evidence-based policymaking at the present of the COVID-19 pandemic and other public health issues. We aggregated weekly average human mobility data derived from the Facebook origin and destination Movement dataset. and weekly average new cases of COVID-19 at the district level from 01-Jun-2021 to 26-Dec-2021 (a total of 30 weeks). We mapped the spatiotemporal dynamics of human mobility and COVID-19 cases across countries in SEA. We further adopted the Geographically and Temporally Weighted Regression model to identify the spatiotemporal variations of the association between human mobility and COVID-19 infections over 30 weeks. Our model also controls for socioeconomic status, vaccination, and stringency of intervention to better identify the impact of human mobility on COVID-19 spread. The percentage of districts that presented a statistically significant association between human mobility and COVID-19 infections generally decreased from 96.15% in week 1 to 90.38% in week 30, indicating a gradual disconnection between human mobility and COVID-19 spread. Over the study period, the average coefficients in 7 SEA countries increased, decreased, and finally kept stable. The association between human mobility and COVID-19 spread also presents spatial heterogeneity where higher coefficients were mainly concentrated in districts of Indonesia from week 1 to week 10 (ranging from 0.336 to 0.826), while lower coefficients were mainly located in districts of Vietnam (ranging from 0.044 to 0.130). From week 10 to week 25, higher coefficients were mainly observed in Singapore, Malaysia, Brunei, north Indonesia, and several districts of the Philippines. Despite the association showing a general weakening trend over time, significant positive coefficients were observed in Singapore, Malaysia, western Indonesia, and the Philippines, with the relatively highest coefficients observed in the Philippines in week 30 (ranging from 0.101 to 0.139). The loosening interventions in response to COVID-19 in SEA countries during the second half of 2021 led to diverse changes in human mobility over time, which may result in the COVID-19 infection dynamics. This study investigated the association between mobility and infections at the regional level during the special transitional period. Our study has important implications for public policy interventions, especially at the later stage of a public health crisis.

Data-Driven Distributionally Robust Electric Vehicle Balancing for Autonomous Mobility-on-Demand Systems Under Demand and Supply Uncertainties

Electric vehicles (EVs) are being rapidly adopted due to their economic and societal benefits. Autonomous mobility-on-demand (AMoD) systems also embrace this trend. However, the long charging time and high recharging frequency of EVs pose challenges to efficiently managing EV AMoD systems. The complicated dynamic charging and mobility process of EV AMoD systems makes the demand and supply uncertainties significant when designing vehicle balancing algorithms. In this work, we design a data-driven distributionally robust optimization (DRO) approach to balance EVs for both the mobility service and the charging process. The optimization goal is to minimize the worst-case expected cost under both passenger mobility demand uncertainties and EV supply uncertainties. We then propose a novel distributional uncertainty sets construction algorithm that guarantees the produced parameters are contained in desired confidence regions with a given probability. To solve the proposed DRO AMoD EV balancing problem, we derive an equivalent computationally tractable convex optimization problem. Based on real-world EV data of a taxi system, we show that with our solution the average total balancing cost is reduced by 14.49%, and the average mobility fairness and charging fairness are improved by 15.78% and 34.51%, respectively, compared to solutions that do not consider uncertainties.

Disparities in Socioeconomic Factors Mediate the Impact of Racial Segregation Among Patients With Hepatopancreaticobiliary Cancer.

Structural racism within the U.S. health care system contributes to disparities in oncologic care. This study sought to examine the socioeconomic factors that underlie the impact of racial segregation on hepatopancreaticobiliary (HPB) cancer inequities. Both Black and White patients who presented with HPB cancer were identified from the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database (2005-2015) and 2010 Census data. The Index of Dissimilarity (IoD), a validated measure of segregation, was examined relative to cancer stage at diagnosis, surgical resection, and overall mortality. Principal component analysis and structural equation modeling were used to determine the mediating effect of socioeconomic factors. Among 39,063 patients, 86.4 % (n = 33,749) were White and 13.6 % (n = 5314) were Black. Black patients were more likely to reside in segregated areas than White patients (IoD, 0.62 vs. 0.52; p < 0.05). Black patients in highly segregated areas were less likely to present with early-stage disease (relative risk [RR], 0.89; 95 % confidence interval [CI] 0.82-0.95) or undergo surgery for localized disease (RR, 0.81; 95% CI 0.70-0.91), and had greater mortality hazards (hazard ratio 1.12, 95% CI 1.06-1.17) than White patients in low segregation areas (all p < 0.05). Mediation analysis identified poverty, lack of insurance, education level, crowded living conditions, commute time, and supportive income as contributing to 25 % of the disparities in early-stage presentation. Average income, house price, and income mobility explained 17 % of the disparities in surgical resection. Notably, average income, house price, and income mobility mediated 59 % of the effect that racial segregation had on long-term survival. Racial segregation, mediated through underlying socioeconomic factors, accounted for marked disparities in access to surgical care and outcomes for patients with HPB cancer.

Large-Area Metal-Semiconductor Heterojunctions Realized via MXene-Induced Two-Dimensional Surface Polarization.

Direct MXene deposition on large-area 2D semiconductor surfaces can provide design versatility for the fabrication of MXene-based electronic devices (MXetronics). However, it is challenging to deposit highly uniform wafer-scale hydrophilic MXene films (e.g., Ti3C2Tx) on hydrophobic 2D semiconductor channel materials (e.g., MoS2). Here, we demonstrate a modified drop-casting (MDC) process for the deposition of MXene on MoS2 without any pretreatment, which typically degrades the quality of either MXene or MoS2. Different from the traditional drop-casting method, which usually forms rough and thick films at the micrometer scale, our MDC method can form an ultrathin Ti3C2Tx film (ca. 10 nm) based on a MXene-introduced MoS2 surface polarization phenomenon. In addition, our MDC process does not require any pretreatment, unlike MXene spray-coating that usually requires a hydrophilic pretreatment of the substrate surface before deposition. This process offers a significant advantage for Ti3C2Tx film deposition on UV-ozone- or O2-plasma-sensitive surfaces. Using the MDC process, we fabricated wafer-scale n-type Ti3C2Tx-MoS2 van der Waals heterojunction transistors, achieving an average effective electron mobility of ∼40 cm2·V-1·s-1, on/off current ratios exceeding 104, and subthreshold swings of under 200 mV·dec-1. The proposed MDC process can considerably enhance the applications of MXenes, especially the design of MXene/semiconductor nanoelectronics.

Wafer‐Scale, Highly Uniform Surface Functionalization from Vapor Phase and Applications to Organic Transistors

AbstractThe surface functionalization by self‐assembled monolayers (SAMs) favors well‐packed organic semiconductor growth and reduces interfacial traps, which assists in developing high‐performance organic thin‐film transistors (OTFTs). Herein, the conventional SAM growth from the vapor phase is ameliorated and systematically studied. With 1H,1H,2H,2H‐Perfluorodecyltrichlorosilane as an example, it is found that deposition temperature of no less than 120 °C and deposition pressure of up to 0.02 bar is preferred for SAM deposition without morphological defects. The optimized SAMs are ultrasmooth with a surface roughness of 0.09 nm and can be escalated to wafer scale. It is verified that the growth condition is universal for other trichlorosilane species. Finally, it is shown that the OTFTs with defect‐free SAMs can achieve an average mobility of 1.79 cm2 V−1 s−1 using dinaphtho(2,3‐b:2′,3′‐f)thieno(3,2‐b)thiophene as the active layer, which is 2.06 times to the devices with defective SAMs and paces up the large‐area and high‐performance organic electronics.

Influence of doping and thickness on domain avalanches in lead zirconate titanate thin films

In undoped lead zirconate titanate films of 1–2 μm thick, domain walls move in clusters with a correlation length of approximately 0.5–2 μm. Band excitation piezoresponse force microscopy mapping of the piezoelectric nonlinearity revealed that niobium (Nb) doping increases the average concentration or mobility of domain walls without changing the cluster area of correlated domain wall motion. In contrast, manganese (Mn) doping reduces the contribution of mobile domain walls to the dielectric and piezoelectric responses without changing the cluster area for correlated motion. In both Nb and Mn doped films, the cluster area increases and the cluster density drops as the film thickness increases from 250 to 1250 nm. This is evident in spatial maps generated from the analysis of irreversible to reversible ratios of the Rayleigh coefficients.

Synthesis, Photophysical properties and OFET application of thienothiophene and benzothiadiazole based Donor-π-Acceptor-π (D-π -A-π) type conjugated polymers

Novel conjugated donor- π -acceptor- π (D- π -A- π) type polymers (P1-P3), possessing thieno[3,2-b]thiophene (TT) with different aromatic substituents as donors, benzo[1–3]thiadiazole (BT) as an acceptor and thiophene as a π -linker, were designed and synthesized via palladium-catalyzed Stille coupling reaction. Their electronic, optical and thermal properties were investigated using UV–vis and fluorescence spectroscopies, cylic voltammetry, and thermal gravimetric analysis. Photophysical characterizations of these novel polymers showed a remarkable mega Stokes shift, reaching up to 130 nm and optic/electronic band gaps between 1.70 and 2.00 eV, as well as good thermal stability of degradation temperature at around 260 °C. To study the effect of electron donating and withdrawing groups on the electronic properties of the π -extended polymers, their organic field-effect transistors (OFETs) were fabricated and charge transport characteristics were investigated. While all three polymers showed a p-type field-effect behaviour, dimethylamine substituted P3 exhibited the highest average saturated hole mobility, μsat, 0.04 cm2 V−1 s−1, on/off current ratio, Ion/Ioff = 3.0 × 103, and the smallest subthreshold swing, SS, 250 mV dec-1, outperforming similar p-type D- π -A- π semiconducting polymers reported in the literature. The results presented in this work corroborate that the three novel TT-BT polymers have promising potential for electronic and optoelectronic applications, in particular where the tunability of field-effect behaviour is essential for performance.

Comparison of Functional Outcomes After Acute Inpatient Rehabilitation After Acquired Brain Injury Before and During the COVID-19 Pandemic.

The objective of this study was to characterize and compare functional outcomes of acquired brain injury patients in an inpatient rehabilitation facility in the year before (April 2019-March 2020) and during the first year (April 2020-March 2021) of the COVID-19 pandemic, when the most drastic changes in the delivery of health care occurred. In this retrospective single-center chart review study, functional outcomes, based on the Center for Medicare and Medicaid Services Inpatient Rehabilitation Facility-Patient Assessment Instrument, were obtained and analyzed for patients in acute inpatient rehabilitation with acquired brain injury. Data from 1330 patients were included for analysis. Functional outcomes of average self-care, bed mobility, and transfer scores were statistically, but not clinically, different between groups. More patients in the pandemic group were discharged home (prepandemic n = 454 [65.4%]; pandemic n = 461 [72.6%]; P = 0.011), although they had significantly longer lengths of stay (prepandemic median = 14.0 [interquartile range = 9.0-23.0]; pandemic = 16.0 [10.0-23.0]; P = 0.037). Despite the impact of hospital policies due to the COVID-19 pandemic, similar functional outcomes were obtained for those with acquired brain injury after inpatient rehabilitation.

Tetramethylammonium Iodide Additive for Enhancing the Charge Carrier Mobilities of Diketopyrrolopyrrole‐Based Conjugated Polymer in Ambipolar Organic Field‐Effect Transistors†

Comprehensive SummaryDiketopyrrolopyrrole (DPP) is one of the most promising building blocks for constructing polymer semiconductors with high charge‐carrier mobilities in organic field‐effect transistors (OFETs). In this study, a novel DPP‐based conjugated polymer, PDPPy‐BDD, was designed and synthesized. The ambipolar field‐effect transistor characteristics were realized with the average hole and electron mobilities of 3.5 × 10–3 and 3.07 × 10–2 cm2 V−1 s−1, respectively. Both the hole and electron mobilities could be successfully enhanced by using a tetramethylammonium iodide (NMe4I) additive. Such an enhancement was attributed to the formation of stronger interchain π–π stackings, the weakening of the face‐on packing orientation in the thin film state, and the higher channel conductivities in the OFETs.

Highly Efficient, Low‐Dose, and Ultrafast Carbazole X‐Ray Scintillators

AbstractOrganic fluorescence scintillators, owing to the ultrafast response time, versatile chemical structures, low processing temperature, and low cost, are considered as one of the promising materials for medical diagnostics, radiation detection, and X‐ray astronomy. However, the low radioluminescence (RL) intensity and low sensitivity hinder their practical applications. In this work, a highly efficient organic fluorescent scintillator, 4,4′‐bis(9‐carbazolyl)biphenyl (CBP), is presented, exhibiting a high X‐ray RL intensity, narrow full width at half‐maximum of 49 nm, and ultrafast decay time of 1.15 ns. More importantly, it has a low detection limit of 25.5 nGy s−1, which is only 1/215 dose rate compared with the commercial X‐ray diagnostics. Such an excellent scintillation performance is mainly attributed to its high photoluminescence quantum yield (PLQY = 61.92%) and good carrier transport (average hole mobility of 0.094 cm2 V−1 s−1). By mixing the CBP into polydimethylsiloxane, the fabricated large area flexible film can be applied in X‐ray radiography, which exhibits a high spatial resolution of 14.3 lp mm−1 at MTF &gt; 0.2. This work paves a way for the implementation of organic fluorescence dyes with high PLQY, high carrier mobility in efficient X‐ray scintillation and imaging.

Mesoscopic Characterization of the Early Stage of the Glucono-δ-Lactone-Induced Gelation of Milk via Image Analysis Techniques.

We provide a method for quantifying the kinetics of gelation in milk acidified with glucono-δ-lactone (GDL) using image analysis techniques, particle image velocimetry (PIV), differential variance analysis (DVA) and differential dynamic microscopy (DDM). The gelation of the milk acidified with GDL occurs through the aggregation and subsequent coagulation of the casein micelles as the pH approaches the isoelectric point of the caseins. The gelation of the acidified milk with GDL is an important step in the production of fermented dairy products. PIV qualitatively monitors the average mobility of fat globules during gelation. The gel point estimated by PIV is in good agreement with that obtained by rheological measurement. DVA and DDM methods reveal the relaxation behavior of fat globules during gelation. These two methods make it possible to calculate microscopic viscosity. We also extracted the mean square displacement (MSD) of the fat globules, without following their movement, using the DDM method. The MSD of fat globules shifts to sub-diffusive behavior as gelation progresses. The fat globules used as probes show the change in matrix viscoelasticity caused by the gelling of the casein micelles. Image analysis and rheology can be used complementarily to study the mesoscale dynamics of the milk gel.

Water‐Surface‐Mediated Precise Patterning of Organic Single‐Crystalline Films via Double‐Blade Coating for High‐Performance Organic Transistors

AbstractApplication‐oriented growth of patterned organic semiconductor (OSC) thin films with a single domain is a nonnegotiable requirement for the manufacturing of high‐performance organic electronic devices. However, the prevalent selective‐wetting patterning method remains a challenge in controlling the density of nucleation events in microscale spaces, resulting in thin films with high grain boundary density and no preferential orientation spherulites. Herein, a simple double‐blade‐coating printing technique using a combination of wetting‐patterned substrates to produce an array of highly crystalline OSC thin films is developed. Specifically, the approach confines the OSC crystallization on a molecular‐flat water surface in specific areas, enabling a significant reduction in the number of nuclei. Consequently, patterned 2,7‐dioctyl[1]benzothieno[3,2‐b] benzothiophene (C8‐BTBT) thin films comprising single‐crystal domains are achieved with an exceptionally high yield of 62.5%. The organic field‐effect transistor array developed from such patterns of C8‐BTBT single‐crystalline films exhibits an excellent average mobility of 11.5 cm2 V−1 s−1 which is 12.5‐fold higher compared to that of the reference sample fabricated via conventional single‐blade coating. It is believed that this approach can be widely applied to other soluble organic materials, thereby opening up opportunities for fabricating multicomponent integrated electronics.

Low-Operating-Voltage Two-Dimensional Tin Perovskite Field-Effect Transistors with Multilayer Gate Dielectrics Based on a Fluorinated Copolymer.

The fabrication of organic-inorganic perovskite field-effect transistors (FETs) with polymer gate dielectrics is challenging because of the solvent corrosion and wettability issues at interfaces. A few polymers have been integrated into perovskite transistors; however, these devices have high operating voltages due to low dielectric constants. Herein, poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) with a high dielectric constant is introduced into bottom-gate phenylethylammonium tin iodide perovskite [(PEA)2SnI4] FETs. Polytetrafluoroethylene (PTFE) and cross-linked poly(4-vinylphenol) (PVP) (CL-PVP) are used to address the issues of solvent corrosion and wettability. We design the PVDF-TrFE/PTFE and PVDF-TrFE/PTFE/CL-PVP dielectric layers, where the ferroelectric properties of PVDF-TrFE are reduced by PTFE. The (PEA)2SnI4 FETs operate at relatively low gate voltages, exhibiting good overall performance with average hole mobilities of 0.42 and 0.36 cm2 V-1 s-1. Our findings provide a feasible strategy for constructing low-operating-voltage perovskite FETs with large-dielectric-constant ferroelectric polymers as gate dielectrics by a solution processing technique.

A clustering-based approach to quantifying socio-demographic impacts on urban mobility patterns

This paper uses a generalizable clustering approach to investigate the effects of socio-demographic features on aggregate urban mobility patterns, including activity distribution and travel modal split. We use K-means via principal component analysis to identify eight representative traveler clusters from the 2017 U.S. National Household Travel Survey. Based on the cluster centroids and the cluster percentages within a neighborhood, we can estimate a Temporal Mobility Choice Matrix ( TM) that describes the neighborhood-level aggregate mobility choice pattern. The estimation accuracy is assessed in a case study in LA City. It is found that the neighborhood-level temporal mobility patterns are well-replicated, with an average R2 of 65.47%, 53.15%, and 72.04% among all analyzed neighborhoods in the city. However, we find a moderate to low accuracy in estimating the spatial differences in the mobility patterns across neighborhoods. This could be because factors other than socio-demographics, such as physical and built environment factors like terrain, street quality, or amenity densities, are contributing to the spatial differences but have not been considered in this study. Overall, we show that socio-demographic features alone can approximate the average temporal mobility choice patterns of a given population. Our method and result can serve as the baseline and benchmark for future mobility studies that take the socio-demographics of the traveler population into consideration in modeling.