Highly efficient flexible perovskite solar cells with vacuum-assisted low-temperature annealed SnO2 electron transport layer

The demand for lightweight, flexible, and high-performance portable power sources urgently requires high-efficiency and stable flexible solar cells. In the case of perovskite solar cells(PSCs), most of the common electron transport layer(ETL) needs to be annealed for improving the optoelectronic properties,while conventional flexible substrates could barely stand the high temperature. Herein, a vacuumassisted annealing SnO_(2) ETL at low temperature(100℃) is utilized in flexible PSCs and achieved high efficiency of 20.14%. Meanwhile, the open-circuit voltage(V_(oc)) increases from 1.07 V to 1.14 V. The flexible PSCs also show robust bending stability with 86.8% of the initial efficiency is retained after 1000 bending cycles at a bending radius of 5 mm. X-ray photoelectron spectroscopy(XPS), atomic force microscopy(AFM), and contact angle measurements show that the density of oxygen vacancies, the surface roughness of the SnO_(2) layer, and film hydrophobicity are significantly increased, respectively. These improvements could be due to the oxygen-deficient environment in a vacuum chamber, and the rapid evaporation of solvents. The proposed vacuum-assisted low-temperature annealing method not only improves the efficiency of flexible PSCs but is also compatible and promising in the large-scale commercialization of flexible PSCs.

Stabilizing α-phase FAPbI3 solar cells

Organic–inorganic hybrid perovskite solar cells(PSCs)have been recognized as a promising and cost-effective photovoltaic technology with the power conversion efficiency(PCE) exceeding 25%[1–3]. The high efficiency is attributed to the exceptional optoelectronic properties, such as high absorption coefficient, long carrier diffusion length, low non-radiative recombination rate, and so on[4–7].

Trends in the prevalence and incidence of chronic obstructive pulmonary disease among adults aged≥50 years in the United States,2000-2020

Background:Understanding the trends of the prevalence and incidence rate of chronic obstructive pulmonary disease(COPD)is vital for improving the control and prevention of COPD.We aimed to examine the trends in the prevalence and incidence rate of COPD among adults aged 50 years or older in the United States during 2000-2020.Methods:Utilizing data from the Health and Retirement Study,we analyzed COPD prevalence across survey waves and calculated COPD incidence rates between consecutive interview waves,stratified by gender and race.We employed joinpoint regression models to investigate trends in COPD prevalence and incidence.Results:The individuals reporting COPD are more likely to be women and Caucasians.The age-adjusted prevalence of COPD among adults aged 50 years and over showed an increasing trend throughout the study period,spanning from 9.02%in 2000 to 9.88%in 2020(average biennial percent change[ABPC]=0.41,95%confidence interval[CI]:0.10,0.71;p=0.01).The age-adjusted incidence rate of COPD among adults aged 50 and over showed a decreasing trend throughout the study period 1031.1 per 100,000 person-years in 2000 to 700.5 per 100,000 person-years in 2020(ABPC=-1.63,95%CI:-2.88,-0.36;p=0.02).Conclusion:Our findings indicate a rising prevalence of COPD among older adults in the United States since 2000,while the incidence rate of COPD has shown a declining trend.

The issues on the commercialization of perovskite solar cells

Perovskite solar cells have aroused a worldwide research upsurge in recent years due to their soaring photovoltaic performance,ease of solution processing,and low cost.The power conversion efficiency record is constantly being broken and has recently reached 26.1%in the lab,which is comparable to the established photovoltaic technologies such as crystalline silicon,copper indium gallium selenide and cadmium telluride(CdTe)solar cells.Currently,perovskite solar cells are standing at the entrance of industrialization,where huge opportunities and risks coexist.However,towards commercialization,challenges of up-scaling,stability and lead toxicity still remain,the proper handling of which could potentially lead to the widespread adoption of perovskite solar cells as a low-cost and efficient source of renewable energy.This review gives a holistic analysis of the path towards commercialization for perovskite solar cells.A comprehensive overview of the current state-of-the-art level for perovskite solar cells and modules will be introduced first,with respect to the module efficiency,stability and current status of industrialization.We will then discuss the challenges that get in the way of commercialization and the corresponding strategies to address them,involving the upscaling,the stability and the lead toxicity issue.Insights into the future direction of commercialization of perovskite photovoltaics was also provided,including the flexible perovskite cells and modules and perovskite indoor photovoltaics.Finally,the future perspectives towards commercialization are put forward.

In-situ artificial retina with all-in-one reconfigurable photomemristor networks

Despite that in-sensor processing has been proposed to remove the latency and energy consumption during the inevitable data transfer between spatial-separated sensors,memories and processors in traditional computer vision,its hardware implementation for artificial neural networks(ANNs)with all-in-one device arrays remains a challenge,especially for organic-based ANNs.With the advantages of biocompatibility,low cost,easy fabrication and flexibility,here we implement a self-powered in-sensor ANN using molecular ferroelectric(MF)-based photomemristor arrays.Tunable ferroelectric depolarization was intentionally introduced into the ANN,which enables reconfigurable conductance and photoresponse.Treating photoresponsivity as synaptic weight,the MFbased in-sensor ANN can operate analog convolutional computation,and successfully conduct perception and recognition of white-light letter images in experiments,with low processing energy consumption.Handwritten Chinese digits are also recognized and regressed by a large-scale array,demonstrating its scalability and potential for low-power processing and the applications in MF-based in-situ artificial retina.

Molecular ferroelectric/semiconductor interfacial memristors for artificial synapses

With the burgeoning developments in artificial intelligence,hardware implementation of artificial neural network is also gaining pace.In this pursuit,ferroelectric devices(i.e.,tunneling junctions and transistors)with voltage thresholds were recently proposed as suitable candidates.However,their development is hindered by the inherent integration issues of inorganic ferroelectrics,as well as poor properties of conventional organic ferroelectrics.In contrast to the conventional ferroelectric synapses,here we demonstrated a two-terminal ferroelectric synaptic device using a molecular ferroelectric(MF)/semiconductor interface.The interfacial resistance can be tuned via the polarization-controlled blocking effect of the semiconductor,owing to the high ferroelectricity and field amplification effect of the MF.Typical synaptic features including spike timing-dependent plasticity are substantiated.The introduction of the semiconductor also enables the attributes of optoelectronic synapse and in-sensor computing with high image recognition accuracies.Such interfaces may pave the way for the hardware implementation of multifunctional neuromorphic devices.

Data-driven design of high-performance MASnxPb1-xI3 perovskite materials by machine learning and experimental realization

The photovoltaic performance of perovskite solar cell is determined by multiple interrelated factors,such as perovskite compositions,electronic properties of each transport layer and fabrication parameters,which makes it rather challenging for optimization of device performances and discovery of underlying mechanisms.Here,we propose and realize a novel machine learning approach based on forward-reverse framework to establish the relationship between key parameters and photovoltaic performance in high-profile MASnxPb1-xI3 perovskite materials.The proposed method establishes the asymmetrically bowing relationship between band gap and Sn composition,which is precisely verified by our experiments.Based on the analysis of structural evolution and SHAP library,the rapid-change region and low-bandgap plateau region for small and large Sn composition are explained,respectively.By establishing the models for photovoltaic parameters of working photovoltaic devices,the deviation of short-circuit current and open-circuit voltage with band gap in defective-zone and low-bandgap-plateau regions from Shockley-Queisser theory is captured by our models,and the former is due to the deep-level traps formed by crystallographic distortion and the latter is due to the enhanced susceptibility by increased Sn4+content.The more difficulty for hole extraction than electron is also concluded in the models and the prediction curve of power conversion efficiency is in a good agreement with Shockley-Queisser limit.With the help of search and optimization algorithms,an optimized Sn:Pb composition ratio near 0.6 is finally obtained for high-performance perovskite solar cells,then verified by our experiments.Our constructive method could also be applicable to other material optimization and efficient device development.

There is plenty of room at the top:generation of hot charge carriers and their applications in perovskite and other semiconductor-based optoelectronic devices

Hot charge carriers(HC)are photoexcited electrons and holes that exist in nonequilibrium high-energy states of photoactive materials.Prolonged cooling time and rapid extraction are the current challenges for the development of future innovative HC-based optoelectronic devices,such as HC solar cells(HCSCs),hot energy transistors(HETs),HC photocatalytic reactors,and lasing devices.Based on a thorough analysis of the basic mechanisms of HC generation,thermalization,and cooling dynamics,this review outlines the various possible strategies to delay the HC cooling as well as to speed up their extraction.Various materials with slow cooling behavior,including perovskites and other semiconductors,are thoroughly presented.In addition,the opportunities for the generation of plasmon-induced HC through surface plasmon resonance and their technological applications in hybrid nanostructures are discussed in detail.By judiciously designing the plasmonic nanostructures,the light coupling into the photoactive layer and its optical absorption can be greatly enhanced as well as the successful conversion of incident photons to HC with tunable energies can also be realized.Finally,the future outlook of HC in optoelectronics is highlighted which will provide great insight to the research community.

Tunable flexible artificial synapses:a new path toward a wearable electronic system

The flexible electronics has been deemed to be a promising approach to the wearable electronic systems.However,the mismatching between the existing flexible deices and the conventional computing paradigm results an impasse in this field.In this work,a new way to access to this goal is proposed by combining flexible devices and the neuromorphic architecture together.To achieve that,a high-performance flexible artificial synapse is created based on a carefully designed and optimized memristive transistor.The device exhibits high-performance which has near-linear non-volatile resistance change under 10,000 identical pulse signals within the 515%dynamic range,and has the energy consumption as low as 45 fJ per pulse.It also displays multiple synaptic plasticity features,which demonstrates its potential for real-time online learning.Besides,the adaptability by virtue of its threeterminal structure specifically contributes its improved uniformity,repeatability,and reduced power consumption.This work offers a very viable solution for the future wearable computing.

Facile synthesis of ironenickelecobalt ternary oxide(FNCO)mesoporous nanowires as electrode material for supercapacitor application

Transition Metal Oxides have drawn significant attention due to their reversible chemical redox reaction and long-life stability.Inexorable agglomeration and shrinkage/expansion of transition metal oxides in the nanosize regime have a noticeable effect on their electrochemical properties.Here in this work,mesoporous nanowires(NWs)with a typical composition of iron-nickel-cobalt ternary oxide(FNCO)are synthesized using a simple,facile and cost-effective hydrothermal process followed by furnace annealing.These NWs are then extensively investigated as an electrode material for supercapacitor application.To compare the electrochemical properties,nanowires of nickel-cobalt oxide(NCO),iron-cobalt oxide(FCO)and cobalt oxide(CO)were also produced by following the same protocol.The FNCO NWs are found to overcome the shortcomings in the electrochemical energy storage devices by exhibiting higher values of specific capacitance(2197 Fg^(-1))and energy density(109 Whkg^(-1))at 1 Ag^(-1) current rate.Moreover,the FNCO NWs also showed a cyclic charge/discharge stability of 96%even up to 20,000 cycles.Furthermore,a FNCO//graphene asymmetric device,fabricated with FNCO NWs and graphene as positive and negative electrodes,respectively,which exhibit high energy density(47 Whkg^(-1)),power density(375 Wkg^(-1))and excellent capacitance retention(86%)after 15,000 cycles.