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Passivation of organic iodides without annealing induces the formation of iodine interstitial (Ii) defects. The cations of organic iodides with appropriate structures can suppress Ii migration, leading to a device efficiency of 24.20% and enhanced operational stability.

Matched energy level alignment and minimal non-radiative recombination at the buried perovskite/charge transport material interface are essential for efficient electron transfer and highly-efficient perovskite solar cells (PSCs). Herein, we develop a facile and feasible method by inserting Cesium(I) Bis(trifluoromethanesulfonyl)imide (CsTFSI) interlayer to fabricate high performance PSCs with negligible hysteresis. With CsTFSI modification, tin oxide displays less trap density, improved electrical conductivity and better energy level alignment with perovskite, leading to a considerable increase in power conversion efficiency (PCE). Consequently, the champion target device presents a PCE of 22.05%, much higher than that of the control device (19.93%). Our work provides an effective and simple strategy for the modification of perovskite buried interface to obtain highly efficient PSCs.

Actively controlling the performance of surface-enhanced Raman scattering (SERS) holds great promise in enabling novel applications of this technique. As a popular two-dimensional material, graphene shows intriguing tunable properties and thus has become a promising material in many potential active device applications. Here we proposed and experimentally demonstrated low-voltage electrically tunable SERS by using a plasmonic gold nanorod-graphene/ion-gel hybrid structure. The SERS signals of molecules adsorbed on such a structure were found to be continuously tunable through an external small bias voltage. As such a tuning process is highly related with the charge transfer between the adsorbed molecules and graphene, the proposed design is also helpful in understanding the charge transfer-based enhancement mechanism of SERS.

Freezing-induced hydrate formation from MgCl2 aqueous solution was monitored using terahertz time-domain spectroscopy.

Semitransparent organic solar cells (STOSCs) are consisted of semitransparent active layer with a structure of both top and bottom transparent electrodes and can be used as power generation windows for both electricity generation and light transmission. In order to better realize these two functions, numerous attentions have been paid on the transparent top electrodes to acquire excellent transparency and maintain high conductivity, as well as the novel photoactive materials to achieve the absorption of near-infrared region. Herein, we review recent advances in a variety of transparent top electrodes and active materials for highly efficient STOSCs, moreover, we also further highlight the application of optical engineering in STOSCs, and give some thoughts about these STOSCs.

The interaction of MgCl

Organic–inorganic hybrid perovskite solar cells (PSCs) have made unprecedented progress in the past ten years, the power conversion efficiency of which increased from 3.8% in 2009 to 25.5% in 2020. The choice of hole transport layers (HTLs) is a key factor for achieving efficient and stable PSCs. Recently, 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD) has been proven to be the most suitable small molecule HTL material in n–i–p PSCs. However, the conductivity and hole mobility of spiro-OMeTAD are dependent on the dopants. Bis(trifluoromethane)sulfonamide lithium salt (LiTFSI) and 4-tert-butylpyridine (TBP) have become the standard HTL dopants to improve the charge transport properties of n–i–p PSCs. Both of these two dopants are effective but have a negative impact on the device stability (induced by ion migration, hygroscopicity, and corrosiveness). In response, lots of efforts have been devoted to the development of alternative and new dopants. In this review, the influence of different doping strategies and corresponding doping mechanisms on device performance and stability was mainly discussed. The stability issues of doped spiro-OMeTAD based PSCs were also described. Finally, we proposed some possible future research goals for dopants based on these existing results to obtain long-lasting and high-efficiency PSCs.

Due to the compromise between exciton diffusion length and light absorption, the active layer thickness of organic solar cells (OSCs) is limited. As we all know, embedding metal nanostructures into OSCs can improve the performance of OSCs by triggering surface plasma resonance, scattering, and other effect without increasing the physical thickness of light trapping layer. Besides, the plasma response and other roles will distinguish when metal nanostructures are embedded into different position of OSCs, which are equally important to the performance of OSCs. In this paper, the enhancement mechanisms of various metal nanostructures in different layers of OSCs are summarized from the electricity and optics aspects. This review also further highlights the progress of plasma effect and their working mechanism in OSCs, and it is expected to provide more perspective of plasma effect for performance enhancement of OSCs.

Low-temperature solution-processed ZnO has decided advantages in flexible and tandem solar cells, while its application encountered difficulties in perovskite optoelectronic devices due to chemical instability at the ZnO–perovskite interface. It has been proven to be a result of protonation reaction between ZnO and organic cations in perovskite materials, thus accelerating the perovskite decomposition. Herein, considering this degradation mechanism, the enhanced interface stability is demonstrated by eliminating the deprotonization ability of ZnO with the modification of methylammonium chloride (MACl), even contacting it with high acidic MA-based perovskite (MAPbI3). After thermal stressing, the film appearance, light absorbance and crystal structure of MAPbI3 on the modified ZnO layer can maintain their initial states, and the long-term stability of MAPbI3-based perovskite solar cells (PSCs) is greatly strengthened. Meanwhile, for CsPbI2Br-based PSCs without organic cations, an improved efficiency not only reveals the foreseeable defect passivation effect of residual Cl but also certifies the great potential of the MACl modified ZnO layer in inorganic PSCs. This study overcomes the shortcomings of ZnO in PSCs comprising organic cations-based perovskite photoactive layer and provides an excellent candidate for a variety of other optoelectronic fields based on perovskite materials.

Organic-inorganic hybrid perovskite solar cells (PSCs) has achieved the power conversion efficiency (PCE) of 25.2% in the last 10 years, and the PCE of inverted PSCs has reached22%. The rapid enhancement has partly benefited from the employment of suitable hole transport layers. Especially, poly(3,4-ethenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is one of the most widely used polymer hole transport materials in inverted PSCs, because of its high optical transparency in the visible region and low-temperature processing condition. However, the PCE and stability of PSCs based on pristine PEDOT:PSS are far from satisfactory, which are ascribed to low fitness between PEDOT:PSS and perovskite materials, in terms of work function, conductivity, film growth, and hydrophobicity. This paper summaries recent progress regarding to modifying/remedy the drawbacks of PEDOT:PSS to improve the PCE and stability. The systematically understanding of the mechanism of modified PEDOT:PSS and various characteristic methods are summarized here. This Review has the potential to guide the development of PSCs based on commercial PEDOT:PSS.

We systematically studied the ability of 20 alkali halides to form solid hydrates in the frozen state from their aqueous solutions by terahertz time-domain spectroscopy combined with density functional theory (DFT) calculations. We experimentally observed the rise of new terahertz absorption peaks in the spectral range of 0.3-3.5 THz in frozen alkali halide solutions. The DFT calculations prove that the rise of observed new peaks in solutions containing Li+, Na+, or F- ions indicates the formation of salt hydrates, while that in other alkali halide solutions is caused by the splitting phonon modes of the imperfectly crystallized salts in ice. As a simple empirical rule, the correlation between the terahertz signatures and the ability of 20 alkali halides to form a hydrate has been established.

NiO has a perfect-aligned energy level with CH3NH3PbI3 perovskite such that it serves as a hole transport layer (HTL), but NiO-based perovskite solar cells (PSCs) still suffer from low efficiency due to the poor interface contact between the perovskite layer and the NiO HTL, and haphazardly stacked perovskite grains. Herein, poly[(9,9­dioctylfluorenyl­2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)] (PFBT) is introduced between the NiO and perovskite layers in the form of a polymer aggregate to enhance perovskite crystallinity and decrease the interface charge recombination between perovskite and NiO in PSCs, resulting in an improved performance. Moreover, PFBT modified perovskite films showed sharper, smoother, and more compact crystalline grains with fewer grain boundaries, leading to the decreased nonradiative recombination. This study offers a simple strategy to achieve highly efficient PSCs with the incorporation of polymer semiconductor aggregates to passivate the interface between the perovskite and NiO layers.

It is an important strategy to improve the performance of polymer solar cells (PSCs) by incorporating metal nanoparticles into functional layers. Herein, gold (Au)@titanium dioxide (TiO2) plasmonic core-shell nanoparticles (PCSNPs) are synthesized and doped into zinc oxide (ZnO) as hybrid electron transport layer in PSCs. Improved light trapping and electrical conductivity are achieved through localized surface plasma resonance of Au@TiO2 PCSNPs. As a result, the short-circuit current density is apparently enhanced, while remaining the unchanged open-circuit voltage. The maximum PCE of 8.801% is obtained when 1.5 wt% Au@TiO2 PCSNPs are introduced into the ZnO layer. This study provides a new inspiration for the development of high efficiency PSCs.

Hypoxia/reoxygenation (H/R) is used as an in vivo model of ischemia/reperfusion injury, and myocardial ischemia can lead to heart disease. Calcium overload is an important factor in myocardial ischemia–reperfusion injury and can lead to apoptosis of myocardial cells. Therefore, it is of great clinical importance to find ways to regulate calcium overload and reduce apoptosis of myocardial cells, and thus alleviate myocardial ischemia–reperfusion injury. There is evidence that heat shock protein 70 (HSP70) has a protective effect on the myocardium, but the exact mechanism of this effect is not completely understood. Stromal interaction molecule 1 and inositol 1,4,5-triphosphate receptor (STIM/1IP3R) play an important role in myocardial ischemia–reperfusion injury. Therefore, this study aimed to investigate whether HSP70 plays an anti-apoptotic role in H9C2 cardiomyocytes by regulating the calcium overload pathway through STIM1/IP3R. Rat H9C2 cells were subjected to transient oxygen and glucose deprivation (incubated in glucose-free medium and hypoxia for 6 h) followed by re-exposure to glucose and reoxygenation (incubated in high glucose medium and reoxygenation for 4 h) to simulate myocardial ischemia reperfusion-induced cell injury. H9C2 cell viability was significantly decreased, and lactate dehydrogenase (LDH) release and apoptosis were significantly increased after oxygen and glucose deprivation. Transfection of HSP70 into H9C2 cells could reduce the corresponding effect, increase cell viability and anti-apoptotic signal pathway, and reduce the apoptotic rate and pro-apoptotic signal pathway. After hypoxia and reoxygenation, the expression of STIM1/IP3R and intracellular calcium concentration of HSP70-overexpressed H9C2 cells were significantly lower than those of hypoxia cells. Similarly, direct silencing of STIM1 by siRNA significantly increased cell viability and expression of anti-apoptotic protein Bcl-2 and decreased apoptosis rate and expression of pro-apoptotic protein BAX. These data are consistent with HSP70 overexpression. These results suggest that HSP70 abrogates intracellular calcium overload by inhibiting upregulation of STIM1/IP3R expression, thus reducing apoptosis in H9C2 cells and playing a protective role in cardiomyocytes.

The achievable functionalities of metasurfaces are mainly determined by the capability of their unit cells to control the local electromagnetic responses. To realize full control over light, it is highly desired to find a kind of unit cell that can achieve complete control of the phase, amplitude, and polarization, which remains a big challenge and cannot be fully replaced with iteration algorithms. Here, such control is achieved by exploiting interference in a dielectric unit cell composed of multiple meta-atoms, namely, a meta-molecule. This strategy provides sufficient effective geometric degrees of freedom within the meta-molecule to enable full control over its optical properties, as is demonstrated here with a complete meta-molecule database. As a proof-of-concept demonstration, polarization-independent, polarization-dependent, and vectorial meta-holograms are proposed and experimentally characterized. High imaging quality is achieved in both the measured intensity and phase distributions. This is allowed by the ability of the meta-molecules to fully record the information of the target images. This strategy opens a direct way toward optical devices with various desirable functionalities.

Surface-enhanced Raman scattering (SERS) is an ultrahigh sensitive detection technique for a variety of research fields. Both electromagnetic and chemical enhancement mechanisms are generally considered to contribute simultaneously to SERS signals. However, it is difficult to actively control the enhancement of SERS signals after the substrate is fabricated, since tuning one or both of the aforementioned enhancement mechanisms remains an experimental challenge. Here, we propose a method for actively implementing the photoinduced modulation of SERS signals, which is that under UV irradiation, the Fermi level of graphene can be dynamically modulated due to the adsorption and desorption of gas molecules. The method is validated in gas atmospheres of O

Carbon dots (CDs) have significant potential in the chemical decoration, crystal modification, and surface passivation of perovskite photovoltaics. However, incompatibility between the hydrophilic/hygroscopic nature of CDs and moisture sensitive perovskite remains an issue. Solving this problem would yield a significant improvement for stable perovskite devices embedded with CDs. Herein, hydrophobic passivation layers are realized for perovskite solar cells (PSCs) through the surface engineering of CDs, exploiting electrostatic self-assembly of trichloro(3,3,3-trifluoropropyl)silane (C3H4Cl3F3Si) and CDs. The embedded CDs modify perovskite grains and passivate grain boundary defects, thereby promoting the carrier lifetime and charge collection. The inserted C3H4Cl3F3Si insulating layer provides a tunneling junction at the contact of the perovskite and electron transport layer. This tunneling layer can selectively conduct electrons and block holes, which spatially separate photo-generated carriers to suppress their recombination. As a result, the optimized perovskite devices deliver the highest efficiency of 21.12% with a high fill factor of 82.86%. Moreover, the variation of surface wettability can be achieved by the self-assembly of C3H4Cl3F3Si, which improves the stability of perovskite devices by maintaining nearly 90% efficiency for over 30 days' exposure to an ambient atmosphere without encapsulation.

The cooling-induced formation of a hydrate in aqueous NaCl solutions was probed using terahertz time-domain spectroscopy (THz-TDS). It was found that the NaCl hydrate formation is accompanied by the emergence of four new absorption peaks at 1.60, 2.43, 3.34 and 3.78 THz. Combining X-ray diffraction measurements with solid-state based density functional theory (DFT) calculations, we assign the observed terahertz absorption peaks to the vibrational modes of the formed NaCl·2H2O hydrate during cooling. This work shows that THz-TDS based analysis has great potential in studying ionic hydrates and the newly revealed collective vibrational modes could be sensitive indicators to achieve quantitative analysis in phase transitions and lattice dynamics.

Charge carrier recombination occurring in the interface has become a major hindrance impairing the efficiency and stability of perovskite solar cells (PSCs). Passivation of electronic defects at the surface and grain boundaries is one of the most important strategies to suppress charge recombination and improve crystallization in PSCs. Herein, sodium sulfate (Na2SO4) passivation layer was incorporated into the TiO2/perovskite interface to improve charge transfer. Compared to the devices without Na2SO4, the device with the optimized concentration of Na2SO4 solution exhibits an increased short-circuit current density of 22.83 mA/cm2 and an enhanced fill factor of 73.68%, yielding an increased power conversion efficiency from 15.20% to 18.75%. The efficiency improvement is attributed to the decreased defects and traps as well as the enhanced film crystallization quality.

In this letter, the efficiency enhancement of polymer solar cells is achieved via interface modification. The Cs2CO3 is incorporated onto TiO2 electron transport layer, which leads to an increase of power conversion efficiency from 5.25% to 6.88%. The introduction of Cs2CO3 modification layer can improve the contact between active layer and electron transport layer, and the ultrathin Cs2CO3 layer hardly hinders the electron transport due to the quantum tunneling effect, resulting in the improvement of short circuit current and the fill factor.

In this work, the performance of inverted polymer solar cells (PSCs) was enhanced by introducing an organic/inorganic/organic (OIO) composite electron-transporting layer (ETL) with the structure of poly ethylenemine(PEI)/SnO2/poly[(9,9-bis(30-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN). The work function measurement and surface morphology indicate that OIO ETL modulates the energy level between active layer and cathode, and reduces the interfacial defects due to the poor contact between organic material and inorganic substance. Also, the OIO ETL could enhance the light absorption of active layer. Therefore, both a high short-circuit current density and fill factor are obtained in the devices owning an OIO ETL, which leads to a dramatic enhancement of device efficiency from 5.51% to 7.18%, accounting for a 30.30% increase. This novel concept of OIO ETL paves a new path for the future applications in the field of PSCs.

BackgroundAsthma exacerbations accelerate the disease progression, as well as increases the incidence of hospitalizations and deaths. There have been studies on the effects of outdoor air pollution and asthma exacerbations; however, evidence regarding single lag0 and lag1 exposure patterns is inconclusive.ObjectiveTo synthesize evidence regarding the relationship between outdoor air pollution and the asthma exacerbation risk in single lag0 and lag1 exposure patterns.MethodsWe performed a systematic literature search using PubMed, Embase, Cochrane Library, Web of Science, ClinicalTrials, China National Knowledge Internet, Chinese BioMedical, and Wanfang databases until August 1st, 2020. Additionally, we reviewed the reference lists of the relevant articles. Two authors independently evaluated the eligible articles and performed structured extraction of relevant information. Pooled relative risks (RRs) and 95% confidence intervals (CIs) of lag0 and lag1 exposure patterns were estimated using the random-effect models.ResultsEighty-four studies met the eligibility criteria and provided sufficient information for meta-analysis. Outdoor air pollutants were associated with significantly increased risks of asthma exacerbations in both single lag0 and lag1 exposure patterns [lag0: RR (95%CI) (pollutants), 1.057(1.011, 1.103) (air quality index; AQI), 1.007(1.005, 1.010) (PM2.5), 1.009(1.005, 1.012) (PM10), 1.010(1.006, 1.014) (NO2), 1.030(1.011, 1.048) (CO), 1.005(1.002, 1.009) (O3); lag1: RR (95%CI) (pollutants), 1.064(1.022, 1.106) (AQI), 1.005(1.002, 1.008) (PM2.5), 1.007(1.004, 1.011) (PM10), 1.008(1.004, 1.012) (NO2), 1.025(1.007, 1.042) (CO), 1.010(1.006, 1.013) (O3)], except SO2 [lag0: RR (95%CI), 1.004(1.000, 1.007); lag1: RR (95%CI), 1.003(0.999, 1.006)]. Subgroup analyses revealed stronger effects in children and asthma exacerbations associated with other events (including symptoms, lung function changes, and medication use as required).ConclusionThese findings demonstrate that outdoor air pollution significantly increases the asthma exacerbation risk in single lag0 and lag1 exposure patterns.PROSPERO registration numberCRD42020204097 (https://www.crd.york.ac.uk/PROSPERO).Strengths and limitations of this studyWe performed a systematic literature search of six databases (with no specified start date or language limitation).Secondary references were included.Publication bias was assessed by applying Begg’s and Egger’s tests.This study focused on the association between outdoor air pollution and the asthma exacerbation risk in single lag0 and lag1 exposure patterns.There were few available studies regarding the AQI, other events, and death analyses.

Melatonin (MLT), as a neurotransmitter and an endogenous neurohormone, plays an important role in physiological functions through interactions with specific receptors. The conformations of MLT are closely related to its biological activities and functions. However, the internal relationship between the structure and interaction of MLT and its allosteric transition remains unclear. In this work, we obtain the broadband fingerprint terahertz (THz) spectrum of MLT in the range of 0.5-18 THz using the air-plasma terahertz time-domain spectroscopy (THz-TDS) system. DFT calculations are employed to analyze the vibration characteristics of MLT. The result shows that the low-frequency vibrations mainly come from the strong coupling between inter- and intramolecular vibrations, and the contribution of intramolecular vibrations gradually dominates with increasing frequency. Meanwhile, the local vibrations of the different functional groups distribute widely in the THz low-frequency band, relating to the diversity of conformational changes in the molecule. The intermolecular hydrogen bonds (HBs) have distinct resonant responses and play critical roles in the THz low-frequency vibrations. The study reveals the complex characteristics of the resonant coupling of MLT with THz electromagnetic waves. The results will help to understand the conformational preferences of MLT in neural signal transmission processes.

Dopamine (DA) is an essential neurotransmitter and hormone of the nervous system, its structural and conformational properties play critical roles in biological functions and signal transmission processes. Although this neuroactive molecule has been studied extensively, the low-frequency vibration features that are closely related to the conformation and molecular interactions in the terahertz (THz) band still remain unclear. In this study, a broadband THz time-domain spectroscopy (THz-TDS) system in the frequency band of 0.5-18 THz was used to characterize the unique THz fingerprint of DA. In addition, density functional theory (DFT) calculations were performed to analyze the vibrational properties of DA. The results suggest that each THz resonant absorption peak of DA corresponds to specific vibrational modes, and the collective vibration also exists in the broadband THz range. Moreover, the interactions between the DA ligand and the D2 and D3 receptors were investigated by docking, and the simulated THz spectra were obtained. The results indicate the dominant role of hydrogen bonding interactions and the specificity of molecular conformation. This work may help to understand the resonance coupling between THz electromagnetic waves and neurotransmitters.

Aim: This study aims to explore the similarity and difference of hippocampal miRNAomes between humans and mice. Materials & methods: A systematic comparison of the miRNAomes between healthy human and mouse hippocampi was performed using high-throughput sequencing followed by bioinformatic analyses. Results: A novel miRNA termed novel-21–5p and a human-specific miR-656–3p were identified in human hippocampi, which were expressed ubiquitously and predicted to be associated with neural activities. Compared with mouse, abundantly expressed miRNAs in human hippocampus were notably enriched in pathways pertaining to neural activities, such as neurotrophin TRK receptor signaling pathway, axon guidance and synaptic transmission. Expression pattern of orthologous miRNAs between human and mouse hippocampi was conserved. Meanwhile, the expression conservation was positively correlated with the sequence conservation. Conclusion: Hippocampal miRNAomes between humans and mice were overall comparable; the differences in expression or function across species should be considered when constructing mouse models.

The low-frequency absorption spectrum of l -histidine hydrochloride monohydrate (LHHM) over 0.5–4.0 THz was measured by terahertz time-domain spectroscopy (THz-TDS). The comparison between the THz absorption spectra of LHHM and l -histidine (LHis) was made. The two distinctive THz spectra of LHHM and LHis indicate that THz spectroscopy is sensitive to different specimens. The low-temperature THz spectral features of LHHM presented the blue-shift and splitting as the temperature decreased. Solid-state density functional theory (DFT) calculation of the vibrational modes of LHHM was performed for better understanding the THz characteristic spectrum, and the validity of the calculation modes was confirmed by comparing with the experimental observations. Powder X-ray diffraction (PXRD) was also carried out to check the structures of LHHM and LHis.

The low-frequency spectra of gallic acid (GA) and its monohydrate were investigated by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 4.5THz. The dehydration process of GA monohydrate was monitored on-line. The kinetic mechanism of the dehydration process was analyzed depending on the THz spectral change at different temperatures. The results indicate that the diffusion of water molecule dominates the speed of the entire dehydration process. Solid-state density functional theory (DFT) calculations of the vibrational modes of both GA and its monohydrate were performed based on their crystalline structures for better interpreting the experimental THz spectra. The results demonstrate that the characterized features of GA mainly originate from the collective vibrations of molecules. And the interactions between GA and water molecules are responsible for THz fingerprint of GA monohydrate. Multi-techniques including differential scanning calorimetry and thermogravimetry (DSC-TG) and powder X-ray diffraction (PXRD) were also carried out to further investigate GA and its monohydrate.

Terahertz (THz) technology is particularly suitable for non-destructive detection of porcelain sherd due to the unique properties of non-ionizing, high penetration, and broad-spectrum. In this paper, we investigated the reflection characteristics of the pigments and sediments for red and green porcelain sherd of Bayi Kiln made in Shanxi province during the Jin Dynasty by terahertz time-domain spectroscopy (THz-TDS), obtaining the spectral responses of different components. Furthermore, Raman spectroscopy was used as a complementary technique to complete the qualitative analysis of the pigments and sediments. In addition, the reflective THz imaging was performed to visualize the pigments and sediments in different regions of the porcelain sherd, realizing the visual detection of the pattern on the surface of the porcelain sherd. These results show that THz-TDS and THz-imaging can serve as effective tools for the detection and analysis of ancient Chinese porcelain.

Recently, polymer solar cells (PSCs) based on low bandgap thienothiophene-benzodithiophene copolymer have exhibited rapidly raised efficiency, but light soaking phenomena has caused a great impact on device performance. Herein, Al3+ was introduced between indium tin oxides (ITO) electrode and poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) electron extraction layer of PSCs. The incorporated Al3+ could not only effectively fill the defects on the surface of ITO, but also decrease electron transport barrier, which facilitates charge transfer and increases the dissociation of photogenerated excitons. As a consequence, the optimal buffer layer improves the photoconductivity response and suppresses the photocurrent hysteresis phenomena.

To overcome the intrinsic chemical-reduction-activity of highly p-doped PEDOT:PSS and improve the open-circuit voltage (Voc) of planar inverted perovskite solar cells, a kind of oxidized carbon nanorods (OCNRs) is developed by a ball-milling/chemical-oxidation method and incorporated into PEDOT:PSS hole transport layer (HTL). The incorporation of OCNRs can increase the work function of the PEDOT:PSS layer, which avoids the energy-level mismatch between the PEDOT:PSS HTL and the HOMO level of the CH3NH3PbI3 perovskite layer, leading to a relatively high Voc of 1.01 V (vs. 0.92 V for the PEDOT:PSS device). Moreover, the introduction of OCNRs into the PEDOT:PSS HTL increases the grain size and uniformity of the perovskite layer, accompanied by the improved charge transport ability. As a result, the fill factor of perovskite solar cells is increased from 75.4% to 81.7%, and the best power conversion efficiency of 19.02% is achieved.

γ-Aminobutyric acid (GABA) is the chief inhibitory neurotransmitter in the central nervous system, its conformational behavior is critical for selective biological functions and the process of signal transmission. Although this neuroactive molecule has been extensively studied, its vibrational properties related to the conformation and intermolecular interactions in the terahertz (THz) band have not been identified experimentally yet. In this study, we applied a broadband THz time-domain spectroscopy (THz-TDS) system from 0.5 to 18 THz to characterize a unique THz fingerprint of GABA. The density functional theory calculation results agree well with the THz experimental spectrum. The study shows that the vibrational modes of GABA at 1.15 and 1.39 THz originate from distinct collective vibrations. The absorptions at the higher THz frequencies also carry part of collective vibrations, but more reflect the specific and local vibrational information, including the skeleton deformation and the rocking of the functional groups, which are closely associated with the conformation and flexibility of GABA. This study may help to understand the conformational transitions of neurotransmitter molecules and the resonant response to THz waves.

Terahertz spectral features of alkali halide crystals were studied with the combination of broadband terahertz time-domain spectroscopy and the solid-state-based density functional theory calculations. To understand the particular modes of the observed terahertz features of the alkali halide crystals, the resonant modes of KCl and CsCl were analyzed using face-centered cubic and body-centered cubic lattice models, respectively. The results show that the characteristic terahertz absorption peaks could be assigned to the lattice vibration of the ionic crystals. Furthermore, the terahertz responses of a series of alkali halides were recorded, and obvious absorption peaks were observed in each salt in the frequency region below 8.5 THz. What is more interestingly is that the frequencies of these observed peaks are red-shifted with the increases of the mass and radius of the ions. This correlation between the resonant frequency of the lattice vibration, the reduced atomic mass, and the equilibrium distance between the ions agrees well with the harmonic oscillator model.

Terahertz spectroscopy provides a powerful and informative link between infrared spectroscopy and microwave spectroscopy, and is now beginning to make its transition from initial development to broader use by chemists, materials scientists and biologists. In this study, utilizing terahertz spectroscopy we monitored the crystallization and isomerization of azobenzene. In flash-frozen trans-azobenzene solutions, the processes of crystallization and phase transition were observed. A new phase has been experimentally confirmed to exist stably at low temperatures. The results on gradual-frozen experiment indicate that the formation of the observed new phase is determined by the cooling rate. Besides, based on the distinctive spectral features of the isomers, the thermal- and photo-induced isomerization processes of azobenzene were investigated. This work presents that the terahertz spectroscopy has a great potential to study the phase transitions and crystallization of liquid samples under different freezing conditions.

Paper and paper products banknotes play an important role in daily life. Two terahertz (THz) time-domain spectrometers (TDS) with combined spectral coverage from 0.5 to 10 THz were used to characterize the optical properties of several types of paper and banknotes. We found that the paper and banknotes show remarkable fingerprints in the terahertz regime, which are highly related to the vibrational modes of the main component of paper and banknotes — cellulose. Meanwhile, THz transmission imaging measurements had been performed and shown the capability of imaging the key anti-counterfeit labels of banknotes such as watermarks, security threads and optically variable inks. The presented study here indicates that the THz spectroscopy together with the imaging method could provide a visible, contactless and nondestructive alternative to delineating paper and paper product banknotes.

Introducing novel nanomaterials into azobenzene (AB) and its derivatives enables a remarkable influence on the molecular isomerization and thus is of great interest for a variety of applications. We systematically study the thermal and photoinduced isomerization of p-aminoazobenzene (pAAB) directly anchored on MoS2/GO nanocomposites by employing in-situ and real-time surface-enhanced Raman scattering (SERS) spectroscopy. The MoS2/GO nanocomposite provides the enhancements for the thermal isomerization efficiency of pAAB of more than 3-fold compared with that of the bare pAAB. We also show that the MoS2/GO nanocomposite has little impact on the UV-induced isomerization of the pAAB, but has apparent impact on the reverse cis-to-trans isomerization of the pAAB under blue light illumination. The results reveal that the effect of MoS2/GO nanocomposite on the photoinduced isomerization of pAAB depends on irradiation wavelength, which can be attributed to the competing interplay of charge transfer and structural relaxation in the hybrid system composed of pAAB and MoS2/GO nanocomposites. The study helps elucidate how the isomerization of azobenzene molecules is affected as incorporated into nanoscale assemblies, and thus open new opportunities for the applications of the isomerization of azobenzene in complex hybrid nanodevices.

The neurotransmitter norepinephrine (NE) was investigated by broadband terahertz time-domain spectroscopy (THz-TDS) in the air-plasma system range from 0.5 to 18.2 THz. NE has a unique absorption spectrum in the THz band, which can be used as a characteristic fingerprint for molecular detection and identification. The temperature-dependent THz spectra of NE were recorded in the range from 83 to 293 K, and a blue-shift of the absorption peaks was observed as the temperature decreased. A solid-state density functional theory (DFT) calculation was implemented to better understand the low-frequency vibrational property of NE, and the calculated results agree well with the THz experimental observations. This result suggests that the broadband THz system can obtain more abundant spectral signals of NE and each THz resonance peak has its own specific vibrational mode, which corresponds to a specific structure and interaction. Even with the adjacent absorption peaks, the vibrational behaviors are different. The deformation of the aromatic ring and the flexibility of the side chain directly affect the NE molecular conformation, which may be closely associated with the receptor binding preference for the neurotransmitter. The conformational diversity of NE may help to understand the biological function of the neurotransmitter in the nervous system.

We present terahertz time-domain spectroscopy (THz-TDS) to explore the conformational dynamics of thermally induced and photoinduced isomerization of azobenzene. The essence of the method is that isomerization of azobenzene proceeds via large structural changes in the molecule, while the THz response is sensitive to these changes. We experimentally demonstrate that the THz spectra of azobenzene show remarkable variations upon heating and irradiation, and as such quantitatively recorded and identified THz spectroscopy can be used to monitor the isomerization process. Specifically, the measured THz spectra clearly reveal that the rate of thermal-isomerization from cis-to-trans in non-polar solvents is faster than that in polar solvents, and an about 6-fold acceleration of the rate could be achieved when Au NPs were introduced as a catalyst into azobenzenes. Moreover, we provide evidence that the temperature and Au NP catalyst do not have an obvious influence on the photoinduced isomerization of azobenzene. The presented example illustrates the power of the THz-TDS method to open up a novel avenue for exploring molecular dynamics.

Now consumer terminal equipment is becoming more and more popular in social life. It has become a very significant research topic to build a proper customization and tailoring model to guide the rapid customization of a dedicated operating system, because of its complex business situation. The existing tailoring and customization technology of Linux operating system cannot meet the customization process of consumer terminal system. To create a more generic and instructive reference model, a hierarchical tailoring and customization model for Linux operating system oriented to application function analysis was proposed, which was based on the component technique of software reuse thinking. This model helps to solve the tailoring and customization of consumer terminal operating systems.

Metal element doping can effectively overcome the drawbacks of transition metal oxide electron transport layer (ETL), such as point defects and unmatched band structure, thereby improving the charge transport and extraction capacity of perovskite solar cells (PSCs). Herein, the application of Co (III) doped compact TiO2 layer for planar heterojunction PSCs is demonstrated. The Co ions replace the Ti ions, which can reduce the oxygen vacancy defects in pristine TiO2, thus decreasing the carrier recombination in electronic trap states and enabling faster electron transport and collection. Co (III) doping can also reduce the work function of TiO2 ETL and adjust its band structure to form a better level alignment, which is beneficial to improving the electron extraction capacity by decreasing the barrier against the electron transport. Meanwhile, the TiO2 ETL with smoother surface leads to a good interface contact. Correspondingly, the quality of perovskite film is also improved. An overall rise of the open-circuit voltage, short-circuit current density and the fill factor are realized, yielding an increased PCE from 16.86% to 19.16%. Our work provides a facile and effective method to solve the problems of non-stoichiometry defects and energy level mismatching for TiO2 or other metal oxide semiconductors transport layer.