Artificial intelligence in physiological characteristics recognition for internet of things authentication

Effective user authentication is key to ensuring equipment security,data privacy,and personalized services in Internet of Things(IoT)systems.However,conventional mode-based authentication methods(e.g.,passwords and smart cards)may be vulnerable to a broad range of attacks(e.g.,eavesdropping and side-channel attacks).Hence,there have been attempts to design biometric-based authentication solutions,which rely on physiological and behavioral characteristics.Behavioral characteristics need continuous monitoring and specific environmental settings,which can be challenging to implement in practice.However,we can also leverage Artificial Intelligence(AI)in the extraction and classification of physiological characteristics from IoT devices processing to facilitate authentication.Thus,we review the literature on the use of AI in physiological characteristics recognition pub-lished after 2015.We use the three-layer architecture of the IoT(i.e.,sensing layer,feature layer,and algorithm layer)to guide the discussion of existing approaches and their limitations.We also identify a number of future research opportunities,which will hopefully guide the design of next generation solutions.

Influence of charge transport layer on the crystallinity and charge extraction of pure tin-based halide perovskite film

As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].

Characterization of hot carrier cooling and multiple exciton generation dynamics in PbS QDs using an improved transient grating technique

Multiple exciton generation （MEG） dynamics in colloidal PbS quantum dots （QDs） characterized with an im- proved transient grating （TG） technique will be reported. Only one peak soon after optical absorption and a fast decay within 1 ps can be observed in the TG kinetics when the photon energy of the pump light hv is smaller than 2.7Eg （Eg： band gap between LUMO and HOMO in the QDs）, which corresponds to hot carrier cooling. When hv is greater than 2.7Eg, however, after the initial peak, the TG signal decreases first and soon increases, and then a new peak appears at about 2 to 3 ps. The initial peak and the new peak correspond to hot carriers at the higher excited state and MEG at the lowest excited state, respectively. By proposing a theoretical model, we can calculate the hot carrier cooling time constant and MEG occurrence time constant quantitatively. When MEG does not happen for hv smaller than 2.7Eg, hot carrier cools with a time con- stant of 400 fs. When MEG occurs for hv larger than 2.7Eg, hot carrier cools with a time constant as small as 200 fs, while MEG occurs with a time constant of 600 fs. The detailed hot carrier cooling and MEG occurrence dynamics characterized in this work would shed light on the further understanding of MEG mechanism of various type of semiconductor QDs.

Surface-Modified Graphene Oxide/Lead Sulfide Hybrid Film-Forming Ink for High-Efficiency Bulk Nano-Heterojunction Colloidal Quantum Dot Solar Cells

Solution-processed colloidal quantum dot solar cells(CQDSCs) is a promising candidate for new generation solar cells.To obtain stable and high performance lead sulfide(PbS)-based CQDSCs,high carrier mobility and low non-radiative recombination center density in the PbS CQDs active layer are required.In order to effectively improve the carrier mobility in PbS CQDs layer of CQDSCs,butylamine(BTA)-modified graphene oxide(BTA@GO) is first utilized in PbS-PbX2(X=I-,Br-) CQDs ink to deposit the active layer of CQDSCs through one-step spin-coating method.Such surface treatment of GO dramatically upholds the intrinsic superior hole transfer peculiarity of GO and attenuates the hydrophilicity of GO in order to allow for its good dispersibility in ink solvent.The introduction of B TA@GO in CQDs layer can build up a bulk nano-heterojunction architecture,which provides a smooth charge carrier transport channel in turn improves the carrier mobility and conductivity,extends the carriers lifetime and reduces the trap density of PbS-PbX2 CQDs film.Finally,the BTA@GO/PbS-PbX2 hybrid CQDs film-based relatively large-area(0.35 cm2) CQDSCs shows a champion power conversion efficiency of 11.7% which is increased by 23.1% compared with the control device.

Colloidal quantum-dot bulk-heterojunction solar cells

Lead sulfide colloidal quantum dots(PbS CQDs),as a nov-el material for optoelectronic devices,have lately attracted a lot of attention mainly because of their tunable optoelectron-ic characteristics and low-temperature film preparation.PbS CQDs can harvest infrared(IR)light in single-junction,multi-junction,and tandem solar cells[1−3].Thanks to the combina-tion of surface chemical engineering and device structure en-gineering,the power conversion efficiency(PCE)for PbS CQDs solar cells has increased from less than 1%in 2005 to current 13.8%[4,5].

Anthradithiophene based hole-transport material for efficient and stable perovskite solar cells

A novel hole-transport material(HTM)based on an anthradithiophene central bridge named BTPA-7 is developed.In comparison to spiro-OMeTAD(2,2’,7,7’-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9’-spirobifluorene),the synthetic steps of BTPA-7 are greatly reduced from 6 to 3 and the synthetic cost of BTPA-7 is nearly a half that of spiro-OMeTAD.Moreover,BTPA-7 exhibits a relatively lower conductivity but higher hole mobility and higher glass transition temperature(Tg)than spiro-OMeTAD.Compared with the photovolatic performance for spiro-OMeTAD,FA0.85MA0.15PbI3 and MAPbI3 PSC devices based on BTPA-7 exhibit slightly lower PCEs with the values of 17.58%(18.88%for spiro-OMeTAD)and 11.90%(13.25%for spiro-OMeTAD),respectively.Nevertheless,a dramatically higher JSC of PSC based on BTPA-7is achieved,which arises from the higher hole mobility of BTPA-7.In addition,the relatively hydrophobic character of BTPA-7 eventually enhances the PSC device stability.Lower cost,higher hole mobility,higher Tg,satisfactory photovoltaic performance,and superior device stability of BTPA-7 can be utilized as a substitute for spiro-OMeTAD in PSCs.

Learning Data Correction for Myoelectric Hand Based on“Survival of the Fittest”

In recent years,myoelectric hands have become multi-degree-of-freedom(DOF)devices,which are controlled via machine learning methods.However,currently,learning data for myoelectric hands are gathered manually and thus tend to be of low quality.Moreover,in the case of infants,gathering accurate learning data is nearly impossible because of the difficulty of communicating with them.Therefore,a method that automatically corrects errors in the learning data is necessary.Myoelectric hands are wearable robots and thus have volumetric and weight constraints that make it infeasible to store large amounts of data or apply complex processing methods.Compared with general machine learning methods such as image processing,those for myoelectric hands have limitations on the data storage,although the amount of data to be processed is quite large.If we can use this huge amount of processing data to correct the learning data without storing the processing data,the machine learning performance is expected to improve.We then propose a method for correcting the learning data through utilisation of the signals acquired during the use of the myoelectric hand.The proposed method is inspired by“survival of the fittest.”The effectiveness of the method was verified through offline analysis.The method reduced the amount of learning data and learning time by approximately a factor of 10 while maintaining classification rates.The classification rates improved for one participant but slightly deteriorated on average among all participants.To solve this problem,verifying the method via interactive learning will be necessary in the future.

How to get high-efficiency lead chalcogenide quantum dot solar cells?

Lead chalcogenide colloidal quantum dots(CQDs)are regarded as attractive absorption materials for novel solar cells(SCs).The cost of lead chalcogenide CQD has been decreased to a commercialization target of$5/g due to the direct production of CQD inks.However,the photoelectric conversion efficiency(PCE)of lead chalcogenide CQDSCs is presently close to 14%,well below the commercialization target(20%),which is only 41%of the theoretical Shockley-Queisser limit efficiency.In this study,the different losses of open-circuit voltage(V_(oc)),fill factor(FF),and short circuit current density(J_(sc))for current CQDSCs are systematically discussed,as well as the percentage and likely causes of each loss.Then the primary reasons for the CQDSCs’performance constraints are highlighted.Following that,we focus on the CQDSCs interfaces(i.e.,CQD/CQD,CQD/HTL,and ETL/CQD)and explore viable ways to reduce device performance loss.Finally,based on the discussion above,we propose many enhancements to significantly solve numerous major obstacles impeding device performance to boost the PCE of CQDSCs for future commercialization significantly.

Femtosecond pulses cleaning by transient-grating process in Kerr-optical media

We use a transient-grating （TG） process in a Kerr bulk medium to clean a femtosecond laser pulse. Using the technique, the temporal contrast of the generated TG signal is improved by more than two orders of magnitude in comparison with the incident pulse in a 0.5-mm-thick fused silica plate. The laser spectrum is smoothed and broadened, and the pulse duration is shortened simultaneously. We expect to extend this technique to a clean pulse with broadband spectral bandwidth at a wide spectral range because it is a phase-matched process.

Super stable CsPbBr3@SiO2 tumor imaging reagent by stress-response encapsulation

Great photoelectric properties can herald the high potentials of CsPbBr3 nanocrystals(NCs)to function as the fluorescent probes for early tumor diagnosis.However,the intrinsic water vulnerability of CsPbBr3 NCs highly restricts their biomedical applications.To conquer this challenge,we herein introduce a nature inspired"stress-response"method to tightly encapsulate CsPbBr3 into SiO2 nano-shells that can dramatically improve the water stability of CsPbBr3@SiO2 nanoparticles for over 48 h.We further highlighted the advantageous features of CsPbBr3@SiO2 by using them as the fluorescent probes for CT26 tumor cell imaging with their high water stability,biocompatibility,and low cytotoxicity.Our work for the first time exhibited the potential of lead halide perovskite NCs for tumor diagnosis,and can highly anticipate the further in vivo biomedical applications that light up live cells.

CsPb(I_(x)Br_(1-x))_(3) solar cells

Owing to its nice performance, low cost, and simple solution-processing, organic-inorganic hybrid perovskite solar cell(PSC) becomes a promising candidate for next-generation high-efficiency solar cells.The power conversion efficiency(PCE) has boosted from 3.8% to 25.2% over the past ten years. Despite the rapid progress in PCE, the device stability is a key issue that impedes the commercialization of PSCs. Recently, all-inorganic cesium lead halide perovskites have attracted much attention due to their better stability compared with their organic-inorganic counterpart. In this progress report, we summarize the properties of CsPb(IxBr1-x)3 and their applications in solar cells. The current challenges and corresponding solutions are discussed. Finally, we share our perspectives on CsPb(IxBr1-x)3 solar cells and outline possible directions to further improve the device performance.