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A detailed investigation on the stability and electronic properties of In n Na 2 ( n = 4–9) clusters is performed by density functional theory, in search for unusually stable motifs. The In 6 Na 2 cluster is characterized by an electronic shell closure with enhanced stability, a larger gap between the highest-occupied and the lowest-unoccupied molecular orbitals, a higher ionization potential, and a lower electronic affinity as compared with adjacent clusters, suggesting that In 6 Na 2 is a magic cluster. Furthermore, the calculated vertical ionization potentials of In n Na 2 agree well with available experimental data, indicating that the obtained structures are good candidates for the ground-state geometries of In n Na 2 .

and low-work-function metals. [ 8 ] Generally, these interlayers have the function of bridging the Fermi energy of the electrode and the energy levels of the organic semiconductor and increasing the built-in electric fi eld in the devices. [ 6 ] Recently, we reported a new category of air stable material, ferroelectric polymer poly(vinylidenefl uoride-trifl uoroethylene) (P(VDFTrFE)), as a universal interlayer, which has tunable and highdensity, aligned dipoles controlled by the external applied bias. [ 9 ] This ferroelectric interlayer can effectively increase or decrease the work function of any electrode to serve as both anode and cathode due to the switchable dipole direction. A strong electric fi eld can be induced in the semiconducting polymers by the unscreened polarization charges of the P(VDF-TrFE), which has been demonstrated to improve the PCE of several types of organic photovoltaic cells (OPVs) to unprecedented values, superior to many other methods. In our previous studies, it was also shown that the polarization of P(VDF-TrFE) on the organic semiconductor fi lms is stable [ 10,11 ] and the surface charges are not screened by photogenerated carriers. [ 10 ]

Balancing and increasing the flux through an engineered heterologous pathway in a target organism to achieve high yield and productivity remains an overwhelming challenge in metabolic engineering. Here we report a novel strategy combining directed evolution and promoter engineering for rapid and efficient multi-gene pathway optimization. As proof of concept, this strategy was applied to optimize a cellobiose utilizing pathway in an industrial Saccharomyces cerevisiae strain for highly efficient cellulosic biofuels production. The resulting strain exhibited significantly higher cellobiose consumption rate (6.41-fold) and ethanol productivity (6.36-fold) compared to its parent strain. This study also showed that both the ratios and absolute values of the expression levels of the genes in the cellobiose utilizing pathway play an important role in cellobiose uptake, and β-glucose is likely one of the key factors affecting cellobiose metabolism.

The successful synthesis and outstanding properties of graphene have promoted strong interest in studying hypothetical graphene-like silicon sheet (silicene). Very recently, 2D silicon nanosheet (Si-NS) stabilized by hexyl groups was reported in experiment. We here present an atomic-level investigation of the geometric stability and electronic properties of Si-NS by density functional calculations and molecular dynamics simulations. The most stable structure of the hexyl-modified Si-NS corresponds to the one in which the hexyl groups are regularly attached to both sides of the sheet, with the periodicity of the hexyl groups on the sheet being 7.17 A, in good agreement with the experimental value of 7.1 A. The electrostatic repulsion effect of the hexyl groups could be an important reason for the favorable structure. The electronic structure of the hexyl-modified Si-NS shows a direct band gap that is not sensitive to the length of the alkyl group but sensitive to the strain effect, which can be used to tun...

Pronounced ferromagnetism was observed in a crystalline blend film of conjugated polymer poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) by using magnetic force microscopy measurements. A substantial room-temperature saturation magnetization of about 0.65 emu g −1 was measured by an alternating gradient field magnetometer. Multiple experimental evidences demonstrate the charge transfer from the P3HT to the PCBM and the formation of P3HT crystal domain are expected to be two critical factors for the originals of room-temperature organic ferromagnetism.

This study reported a novel fluorinated copolymer (FTQ) and shown it to exhibit a significantly higher open circuit voltage (VOC) in bulk heterojunction solar cells with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) compared to the low band-gap polymer Thiophene–Quinoxaline (TQ). Fluorination lowers the polymer HOMO level effectively which pushes down the highest occupied molecular orbital (HOMO) level of the TQ from −5.36 eV to −5.51 eV and increases the relative dielectric constant from 4.2 to 5.5, resulting in a high VOC. The highest VOC of 950 mV was achieved in the FTQ/PCBM solar cell device. For these optimized blends, the device made of FTQ:PC71BM with a 1 : 1 weight ratio yielded a high power conversion efficiency of 5.3% after a very short time thermal annealing process. These findings will be of importance for achieving high-performance of polymer solar cells by functional group substitution in low band gap polymers.

Understanding the influence of light on ion migration in organic–inorganic halide perovskite (OIHP) materials is important to understand the photostability of perovskite solar cells. We reveal that light could greatly reduce the ion migration energy barrier in both polycrystalline and single crystalline OIHP. The activation energies derived from conductivity measurement under 0.25 Sun decrease to less than one half of the values in the dark. A typical ion drift velocity in CH3NH3PbI3 polycrystalline films is 1.2 μm s−1 under 1 Sun, compared with 0.016 μm s−1 under 0.02 Sun. Ion migration across the photoactive layers in most OIHP devices thus takes only subseconds under 1 Sun illumination, which is much shorter than what it was thought to take. Most important of all, ion migration through a single crystal surface is still too slow to be observed even after illumination for two days due to the large ion diffusion activation energy, >0.38 eV.

López Varo, Pilar et al., Solar energy conversion using semiconductors to fabricate photovoltaic devices relies on efficient light absorption, charge separation of electron-hole pair carriers or excitons, and fast transport and charge extraction to counter recombination processes. Ferroelectric materials are able to host a permanent electrical polarization which provides control over electrical field distribution in bulk and interfacial regions. In this review, we provide a critical overview of the physical principles and mechanisms of solar energy conversion using ferroelectric semiconductors and contact layers, as well as the main achievements reported so far. In a ferroelectric semiconductor film with ideal contacts, the polarization charge would be totally screened by the metal layers and no charge collection field would exist. However, real materials show a depolarization field, smooth termination of polarization, and interfacial energy barriers that do provide the control of interface and bulk electric field by switchable spontaneous polarization. We explore different phenomena as the polarization-modulated Schottky-like barriers at metal/ferroelectric interfaces, depolarization fields, vacancy migration, and the switchable rectifying behavior of ferroelectric thin films. Using a basic physical model of a solar cell, our analysis provides a general picture of the influence of ferroelectric effects on the actual power conversion efficiency of the solar cell device, and we are able to assess whether these effects or their combinations are beneficial or counterproductive. We describe in detail the bulk photovoltaic effect and the contact layers that modify the built-in field and the charge injection and separation in bulk heterojunction organic cells as well as in photocatalytic and water splitting devices. We also review the dominant families of ferroelectric materials that have been most extensively investigated and have provided the best photovoltaic performance., The research leading to these results has received funding from the European Union Seventh Framework Program [FP7/2007–2013] under grant agreement 316494 and from MINECO of Spain under project TEC2013-47283-R and Grant FPU12/02712. F.R. acknowledges funding and partial salary support for work on multiferroic materials from NSERC, through an EWR Steacie Memorial Fellowship.

An anomalous photovoltaic effect with open-circuit voltage larger than bandgap is discovered in hybrid perovskite solar cells., Organic-inorganic hybrid perovskites (OIHPs) have been demonstrated to be highly successful photovoltaic materials yielding very-high-efficiency solar cells. We report the room temperature observation of an anomalous photovoltaic (APV) effect in lateral structure OIHP devices manifested by the device’s open-circuit voltage (VOC) that is much larger than the bandgap of OIHPs. The persistent VOC is proportional to the electrode spacing, resembling that of ferroelectric photovoltaic devices. However, the APV effect in OIHP devices is not caused by ferroelectricity. The APV effect can be explained by the formation of tunneling junctions randomly dispersed in the polycrystalline films, which allows the accumulation of photovoltage at a macroscopic level. The formation of internal tunneling junctions as a result of ion migration is visualized with Kelvin probe force microscopy scanning. This observation points out a new avenue for the formation of large and continuously tunable VOC without being limited by the materials’ bandgap.

Ultraweak light detection with solid-state and cooling-free photodetectors is important for both fundamental research and practical applications. A general phototransistor architecture for detecting ultraviolet-visible light down to 100 fW cm

Organometal trihalide perovskite (OTP) solar cells might be the next commercially available thin film solar cells due to its high power conversion efficiency and low fabrication cost, which should be attributed to the fantastic optoelectronic properties of OTP materials. Recent studies disclosed that OTP is actually a kind of soft material with both charge carrier conduction and ionic conduction. Increasing observations indicate that mobile ions impact a lot on the electronic/optoelectric properties of OTP film, which hence have raised substantial related studies already. In this chapter, we will provide critical review about the current understanding of ion migration behaviours in OTP solar cells and discuss its impacts on the photovoltaic device efficiency and stability. Besides, the emerging efforts about suppressing ion migration in perovskite films will be summarized. The purpose of this chapter is to provide a quick and brief introduction of the research progress in the ion migration studies.

Organometal trihalide perovskites have been demonstrated as excellent light absorbers for high-efficiency photovoltaic applications. Previous approaches to increasing the solar cell efficiency have focused on optimization of the grain morphology of perovskite thin films. Here, we show that the structural order of the electron transport layers also has a significant impact on solar cell performance. We demonstrate that the power conversion efficiency of CH3NH3PbI3 planar heterojunction photovoltaic cells increases from 17.1 to 19.4% when the energy disorder in the fullerene electron transport layer is reduced by a simple solvent annealing process. The increase in efficiency is the result of the enhancement in open-circuit voltage from 1.04 to 1.13 V without sacrificing the short-circuit current and fill factor. These results shed light on the origin of open-circuit voltage in perovskite solar cells, and provide a path to further increase their efficiency. Ongoing efforts are devoted to raising the efficiency of solar cells in converting energy from solar radiation. Now, improved structural order in the charge transport layers of perovskite solar cells is shown to increase the efficiency from 17.1% to 19.4%.

Ultraviolet photodetectors have applications in fields such as medicine, communications and defence1, and are typically made from single-crystalline silicon, silicon carbide or gallium nitride p–n junction photodiodes. However, such inorganic photodetectors are unsuitable for certain applications because of their high cost and low responsivity (

A solution-processed fullerene-based organic Schottky junction photovoltaic device is fabricated to produce a large open circuit voltage, 0.85-0.95 V, which is higher than that of most organic bulk-heterojunction devices. A power conversion efficiency of 5% is achieved in fullerene-derivative [6,6]-phenyl-C71-butyric acid methylester-based Schottky junction devices.

Foundation works induce construction vibration, which has a significant influence on the surrounding environment and may damage existing buildings, or disturb occupants or vibration sensitive equipment. The result is a risk faced by project owner which should be predicted before construction. This risk is more difficult to predict and the uncertainty is often greater than for general construction. In this paper, a fuzzy expert system is built based on fuzzy logic to predict the construction vibration risk. The production knowledge structure and Mamdani inference method are used, and the Matlab fuzzy logic toolbox and Simulink are used to develop the system. After describing the fuzzy expert system, this paper provides an example to illustrate the application of the method.

Power conversion properties of perovskite solar cells are studied in the temperature range of 310 K to 240 K (and recovering back). As the temperature lowers down, the fill factor (FF) decreases while the open circuit voltage (VOC) increases in the case of reverse scans (scanning from positive voltages to negative ones). The decreased FF is ascribed to the increased resistance of charge transport materials (both TiO2 and Spiro-OMeTAD) as well as the increased interfacial charge transfer resistance, while the increased VOC is due to retarded recombination which is revealed by the transient photovoltage decay measurement. Hysteresis appears in the current-voltage curves, but it shrinks with temperature decreasing and even vanishes as the temperature becomes lower than 270 K. Mott-Schottky capacitance analysis shows that ion migration exists in the device, especially for temperatures >270 K. The “S shape” current-voltage characteristic is observed at lowered temperatures, which is caused by retarded charge extraction across the interface between the active layer and charge-transport materials. Similar power conversion properties are observed when elevating the temperature from 240 K to 310 K; thus, the temperature-sensitive behavior is reversible. The observed behavior is compared with silicon solar cells. The study shows that lowering the temperature is harmful to the charge extraction processes of perovskite solar cells. Highly conductive charge-transport materials are needed for the devices to operate in a colder environment.Power conversion properties of perovskite solar cells are studied in the temperature range of 310 K to 240 K (and recovering back). As the temperature lowers down, the fill factor (FF) decreases while the open circuit voltage (VOC) increases in the case of reverse scans (scanning from positive voltages to negative ones). The decreased FF is ascribed to the increased resistance of charge transport materials (both TiO2 and Spiro-OMeTAD) as well as the increased interfacial charge transfer resistance, while the increased VOC is due to retarded recombination which is revealed by the transient photovoltage decay measurement. Hysteresis appears in the current-voltage curves, but it shrinks with temperature decreasing and even vanishes as the temperature becomes lower than 270 K. Mott-Schottky capacitance analysis shows that ion migration exists in the device, especially for temperatures >270 K. The “S shape” current-voltage characteristic is observed at lowered temperatures, which is caused by retarded charge e...

Migration of ions can lead to photoinduced phase separation, degradation, and current-voltage hysteresis in perovskite solar cells (PSCs), and has become a serious drawback for the organic-inorganic hybrid perovskite materials (OIPs). Here, the inhibition of ion migration is realized by the supramolecular cation-π interaction between aromatic rubrene and organic cations in OIPs. The energy of the cation-π interaction between rubrene and perovskite is found to be as strong as 1.5 eV, which is enough to immobilize the organic cations in OIPs; this will thus will lead to the obvious reduction of defects in perovskite films and outstanding stability in devices. By employing the cation-immobilized OIPs to fabricate perovskite solar cells (PSCs), a champion efficiency of 20.86% and certified efficiency of 20.80% with negligible hysteresis are acquired. In addition, the long-term stability of cation-immobilized PSCs is improved definitely (98% of the initial efficiency after 720 h operation), which is assigned to the inhibition of ionic diffusions in cation-immobilized OIPs. This cation-π interaction between cations and the supramolecular π system enhances the stability and the performance of PSCs efficiently and would be a potential universal approach to get the more stable perovskite devices.

Straight silver nanowires were synthesized by accelerated oxidization and then aligned into ordered arrays by off-center spin-coating. Seesaw-like behavior was observed in the polarized transmission spectra of the arrays. With the increment of polarization angle (θP, defined as the angle between axis of nanowires and direction of electric field of light), transmission changed repeatedly with a period of 180°, but it moved to opposite directions between the two regions separated by supporting points locating at 494 nm. The behavior is ascribed to the competition between the extinction behaviors of the two modes of surface plasma polaritons on silver nanowires. One is the longitudinal mode which is excited by long wavelengths and tuned by function of cos2( θ p) and the other is the transverse mode that is excited by short wavelengths and tuned by function of sin2( θ p). Simulation was performed based on the finite-difference time domain method. The effect of the nanowire diameter and length (aspect ratio) on the position of the supporting point was studied. As nanowire width increased from 20 nm to 350 nm, the supporting point moved from 400 to 500 nm. While it changed slightly when the nanowire length increased from 3 μm to infinitely long (width fixed at 260 nm). In current study, the position of the supporting point is mainly determined by the nanowire width.

Density functional study was performed on the stability of In n M ( n = 11–15, M = Li, Na, K) clusters. In 13 M are characterized by electronic shell closure with enhanced stability, larger HOMO–LUMO gap, higher ionization potential, and lower electron affinity as compared with clusters of adjacent sizes, while very similar size dependence was found between In n M and Al n M in their electronic properties, suggesting that In 13 M be magic clusters and promising as building blocks in developing cluster-assembled materials. The calculated AEA of In 13 is close to that of iodine, implying it would behave like a halogen atom in ionic In 13 M molecule.

Permeabilization of Corynebacterium glutamicum cells permits direct determination of enzyme activity measuring NAD(P)H after appropriate calibration and correction for cell density. The optimized conditions found were the treatment of 10 mg cells/ml (dry weight) by Triton X-100 at a final concentration of 0.05% for 5 min at room temperature. Glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase activities were very close to those determined in the cell-free extract. In cell-free extracts malic enzyme activity was about double and that of isocitrate dehydrogenase about triple the values in permeabilized cells. K m values were similar in cell-free extract and permeabilized cells, but larger than literature values obtained with purified enzymes.

The structural and electronic properties of In 12 X (X = C, Si, Ge, Sn) and their anions have been investigated using the density functional theory at BLYP and B3LYP levels. The equilibrium geometries of In 12 X (X = Si, Ge, and Sn) and their anions favor the pseudo D 5 h structures, while those of In 12 C and its anion tend to form C s ones. The calculated adiabatic electron affinities of In 12 Si and In 12 Ge are 2.01 and 2.04 eV, respectively, in good agreement with the available experimental data. The magnetic moments of the ground state In 12 X are all zero, indicating that they have closed shell electronic structures. Thus, indium behaves as a trivalent atom in the clusters.

The generalized gradient approximation based on density functional theory is applied to study the structural stability, electronic properties, and static linear polarizability of Ba@C74. It is found that the most favorable endohedral site for a Ba atom is off-center under a [6, 6] double bond along the C2 axis on the σh plane, which is denoted as Ba@C74-2. This result can be explained by the electrostatic potential map of the C 74 2 - on the σh plane. Of particular interest is the static linear polarizability of Ba@C74-2. The calculated polarizability component αzz of Ba@C74-2 687.3 A3 is nine times that of C60 77.4 A3, while αxx and αyy are zero. This large anisotropy may be due to its lower C2v symmetry compared to C60 with Ih-symmetry, as well as the transference of about two valence electrons from the Ba atom to the carbon cage.

The applicability of gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) for the quantification of 13C enrichment of proteinogenic amino acids in metabolic tracer experiments was evaluated. Measurement of the 13C enrichment of proteinogenic amino acids from cell hydrolyzates of Corynebacterium glutamicum growing on different mixtures containing between 0.5 and 10% [1-13C]glucose shows the significance of kinetic isotope effects in metabolic flux studies at low degree of labeling. We developed a method to calculate the 13C enrichment. The approach to correct for these effects in metabolic flux studies using delta13C measurement by GC-C-IRMS uses two parallel experiments applying substrate with natural abundance and 13C-enriched tracer substrate, respectively. The fractional enrichment obtained in natural substrate is subtracted from that of the enriched one. Tracer studies with C. glutamicum resulted in a statistically identical relative fractional enrichment of 13C in proteinogenic amino acids over the whole range of applied concentrations of [1-13C]glucose. The current findings indicate a great potential of GC-C-IRMS for labeling quantification in 13C metabolic flux analysis with low labeling degree of tracer substrate directly in larger scale bioreactors.

The geometric and magnetic properties of the M@Pb12 clusters (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni) are studied using the relativistic density-functional method. The geometric optimization shows that the ground states of these clusters are close to the Ih structure. The magnetism calculations demonstrate that the magnetic moments of M@Pb12 vary from 1 μB to 5 μB by doping different transition-metal atoms into Pb12 cage, therefore, they possess tunable magnetic properties and have potential utility in new nanomaterials. The electronic structure calculation shows that the Mn@Pb12 has large energy gap and doping energy. Furthermore, of particular interesting is that its structure and energy gap remain unchanged with a strong external electric field up to 0.1 V/A, thus, Mn@Pb12 would be a good candidate as the building block with high magnetic moment for cluster assembly.

We describe the first DNA-based storage architecture that enables random access to data blocks and rewriting of information stored at arbitrary locations within the blocks. The newly developed architecture overcomes drawbacks of existing read-only methods that require decoding the whole file in order to read one data fragment. Our system is based on new constrained coding techniques and accompanying DNA editing methods that ensure data reliability, specificity and sensitivity of access, and at the same time provide exceptionally high data storage capacity. As a proof of concept, we encoded parts of the Wikipedia pages of six universities in the USA, and selected and edited parts of the text written in DNA corresponding to three of these schools. The results suggest that DNA is a versatile media suitable for both ultrahigh density archival and rewritable storage applications., Comment: 26 pages, 12 figures

Large-aspect-ratio grains are needed in polycrystalline thin-film solar cells for reduced charge recombination at grain boundaries; however, the grain size in organolead trihalide perovskite (OTP) films is generally limited by the film thickness. Here we report the growth of OTP grains with high average aspect ratio of 2.3–7.9 on a wide range of non-wetting hole transport layers (HTLs), which increase nucleus spacing by suppressing heterogeneous nucleation and facilitate grain boundary migration in grain growth by imposing less drag force. The reduced grain boundary area and improved crystallinity dramatically reduce the charge recombination in OTP thin films to the level in OTP single crystals. Combining the high work function of several HTLs, a high stabilized device efficiency of 18.3% in low-temperature-processed planar-heterojunction OTP devices under 1 sun illumination is achieved. This simple method in enhancing OTP morphology paves the way for its application in other optoelectronic devices for enhanced performance., The performance of hybrid perovskite solar cells is diminished by charge recombination, which commonly occurs at grain boundaries. Here, the authors employ a non-wetting hole transport layer which promotes the growth of highly crystalline films with fewer grain boundaries, leading to improved device efficiencies.

Synthetic biology is an interdisciplinary field that takes top-down approaches to understand and engineer biological systems through design-build-test cycles. A number of advances in this relatively young field have greatly accelerated such engineering cycles. Specifically, various innovative tools were developed for in silico biosystems design, DNA de novo synthesis and assembly, construct verification, as well as metabolite analysis, which have laid a solid foundation for building biological foundries for rapid prototyping of improved or novel biosystems. This review summarizes the state-of-the-art technologies for synthetic biology and discusses the challenges to establish such biological foundries.

The presentation provides the recent advances of our group in developing high efficiency organolead trihalide perovskites thin film and single crystal solar cells, and understanding how perovskite solar cells work.

An effective forecasting model for short-term load plays a significant role in promoting the management efficiency of an electric power system. This paper proposes a new forecasting model based on the improved neural networks with random weights (INNRW). The key is to introduce a weighting technique to the inputs of the model and use a novel neural network to forecast the daily maximum load. Eight factors are selected as the inputs. A mutual information weighting algorithm is then used to allocate different weights to the inputs. The neural networks with random weights and kernels (KNNRW) is applied to approximate the nonlinear function between the selected inputs and the daily maximum load due to the fast learning speed and good generalization performance. In the application of the daily load in Dalian, the result of the proposed INNRW is compared with several previously developed forecasting models. The simulation experiment shows that the proposed model performs the best overall in short-term load forecasting.

Water distribution network is important in the critical physical infrastructure systems. The paper studies the emergency resource strategies on water distribution network with the approach of complex network and cascading failures. The model of cascade-based emergency for water distribution network is built. The cascade-based model considers the network topology analysis and hydraulic analysis to provide a more realistic result. A load redistribution function with emergency recovery mechanisms is established. From the aspects of uniform distribution, node betweenness, and node pressure, six recovery strategies are given to reflect the network topology and the failure information, respectively. The recovery strategies are evaluated with the complex network indicators to describe the failure scale and failure velocity. The proposed method is applied by an illustrative example. The results showed that the recovery strategy considering the node pressure can enhance the network robustness effectively. Besides, this strategy can reduce the failure nodes and generate the least failure nodes per time.

The surface morphology of PEDOT:PSS after mild oxygen plasma treatment were investigated by scanning electron microscopy and atomic force microscopy. The nanometer-scale islands on the surface of treated PEDOT:PSS were observed. Vacuum deposited organic light-emitting diodes (OLEDs) with treated PEDOT:PSS as anode buffer layer had been fabricated. The OLEDs with an appropriately treated PEDOT:PSS as anode buffer layer exhibited significantly enhanced lifetime and decreased driving voltage. The results suggest that the appropriate mild oxygen plasma treatment of PEDOT:PSS layers may be useful for the improvement of the interface with the hole transport layer and enhanced device performance.

The geometric and electronic properties of metal–carbon encaged fullerenes Sc2C2@C84 have been studied using the density functional theory at the Becke exchange gradient correction and the Perdew–Wang correlation gradient correction function level with the double numerical atomic orbitals basis sets augmented by polarization functions. The Sc2C2 cluster was found to be stable in C84 cage, while the cage expands slightly. The Sc2C2 cluster can rotate freely in the cage around the Sc–Sc axis which is coincident with the vertical principal axis of the cage. As the Sc2C2 cluster is encaged, the degeneracy of energy splits, and the HOMO–LUMO energy gap becomes smaller than that of the pure C84, which suggests that Sc2C2@C84 has higher reactivity than C84. Based on our calculated results, the electronic structure of Sc2C2@C84 might be formally described as (Sc2C2)+1@(C84)−1 due to the charge transferring from the Sc2C2 cluster to C84 cage.

The electronic properties of the nonclassical four-membered ring fullerene (4-Me–C6H4)2–C62, H2–C62, and F2–C62 are studied using the density functional theory. The computational results show that, the frontier orbitals of C62, particularly the highest occupied molecular orbital, are localized mainly around the four-membered ring. High stability is predicted for (4-Me–C6H4)2–C62 due to its much larger energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, compared with that of C62. The frontier orbitals theory is used to study the possibility of synthesizing H2–C62 and F2–C62 in which H2 and F2 are used to replace the (4-Me–C6H4)2 in (4-Me–C6H4)2–C62, and the results show that F2–C62 might be much stable and easier to synthesize than H2–C62.

An irreversible light-soaking effect was disclosed in perovskite solar cells using TiO2 as an electron transporting layer. The power conversion efficiency of a fresh device was improved more by twice after light soaking for 15 min and then remained 70% even though the device was recovered in the dark for 4 days. The buried mechanism was explored by shedding light on the interaction between light and titanium dioxide. Oxygen vacancies in TiO2 were found to be increased by light-soaking, especially for wavelengths shorter than 400 nm. Such vacancies enhanced the N-type doping in the semiconductor, which not only increased the conductivity of the titania film but also accelerated the charge extraction rate between perovskite crystallites and titania, and finally contributed to upgraded power conversion efficiency.

Perovskite photodetectors are fabricated via structuring a perovskite/organic heterojunction with CH3NH3PbI3 and a high-mobility and stable organic semiconductor dioctylbenzothieno [2,3-b] benzothiophene (C8BTBT), which possess broad range photoresponse from ultraviolet to near-infrared, fast response, and excellent stability. The CH3NH3PbI3/C8BTBT heterojunction photodetectors exhibit an excellent ratio of photocurrent to dark current, Ilight/Idark, as high as 2.4 × 104, a high responsivity up to 24.8 AW−1, and a fast response of about 4.0 ms. Meanwhile, the photodetectors can maintain 90% performance even exposed in ambient condition without encapsulation for 20 d. In addition, the detailed mechanism is disclosed based on ultraviolet photoemission spectroscopy, steady-state photoluminescence (PL) spectra, and PL lifetime experiments. The C8BTBT layer acts as an efficient hole-extraction layer to let the holes quickly transport to the electrodes due to its perfect filling in the gaps between perovskite grains, as well as its intrinsic high mobility and the energy-level match with the CH3NH3PbI3. The stable C8BTBT layer can well play as a waterproof layer as well to prevent the perovskite CH3NH3PbI3 from the degradation. The research provides an excellent method for fabricating high-performance and stable perovskite photodetectors using perovskite/organic heterojunction.

The nonexcitonic character for organometal trihalide perovskites is demonstrated by examining the field-dependent exciton dissociation behavior. Moreover, it is found that photogenerated excitons can be effectively dissociated into free charges inside perovskite without the assistance of charge extraction layer or external field, which is a stark contrast to the charge-separation behavior in excitonic materials in the same photovoltaic operation system.

DNA assembly is one of the most important foundational technologies for synthetic biology and metabolic engineering. Since the development of the restriction digestion and ligation method in the early 1970s, a significant amount of effort has been devoted to developing better DNA assembly methods with higher efficiency, fidelity, and modularity, as well as simpler and faster protocols. This review will not only summarize the key DNA assembly methods and their recent applications, but also highlight the innovations in assembly schemes and the challenges in automating the DNA assembly methods.

The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CH3NH3PbI3 solar cells. The elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.

Solvent-annealing is found to be an effective method to increase the grain size and carrier diffusion lengths of trihalide perovskite materials. The carrier diffusion length of MAPbI3 is increased to over 1 μm. The efficiency remains above 14.5% when the MAPbI3 thickness changes from 250 nm to 1 μm, with the highest efficiency reaching 15.6%.