Regulation of the quantum barrier and carrier transport toward high-efficiency quasi-2D Dion-Jacobson tin perovskite solar cells

Quasi-2D Dion-Jacobson(DJ)tin halide perovskite has attracted much attention due to its elimination of Van der Waals gap and enhanced environmental stability.However,the bulky organic spacers usually form a natural quantum well structure,which brings a large quantum barrier and poor film quality,further limiting the carrier transport and device performance.Here,we designed three organic spacers with different chain lengths(ethylenediamine(EDA),1,3-propanediamine(PDA),and 1,4-butanediamine(BDA))to investigate the quantum barrier dependence.Theoretical and experimental characterizations indicate that EDA with short chain can reduce the lattice distortion and dielectric confinement effect,which is beneficial to the effective dissociation of excitons and the inhibition of trap-free non-radiative relaxation.In addition,EDA cation shows strong interaction with the inorganic octahedron,realizing large aggregates in precursor solution and high-quality films with improved structural stability.Furthermore,femtosecond transient absorption proves that EDA cations can also weaken the formation of small n-phases with large quantum barrier to achieve effective carrier transport between different nphases.Finally,the quasi-2D DJ(EDA)FA_(9)Sn_(10)I_(31)solar cells achieves a 7.07%power conversion efficiency with good environment stability.Therefore,this work sheds light on the regulation of the quantum barrier and carrier transport through the chain length of organic spacer for qua si-2D DJ lead-free perovskites.

Effect of interface roughness on the carrier transport in germanium MOSFETs investigated by Monte Carlo method

Interface roughness strongly influences the performance of germanium metal-organic-semiconductor field effect transistors （MOSFETs）. In this paper, a 2D full-band Monte Carlo simulator is used to study the impact of interface roughness scattering on electron and hole transport properties in long- and short- channel Ge MOSFETs inversion layers. The carrier effective mobility in the channel of Ge MOSFETs and the in non-equilibriurn transport properties are investigated. Results show that both electron and hole mobility are strongly influenced by interface roughness scattering. The output curves for 50 nm channel-length double gate n and p Ge MOSFET show that the drive currents of n- and p-Ge MOSFETs have significant improvement compared with that of Si n- and p-MOSFETs with smooth interface between channel and gate dielectric. The 82% and 96% drive current enhancement are obtained for the n- and p-MOSFETs with the completely smooth interface. However, the enhancement decreases sharply with the increase of interface roughness. With the very rough interface, the drive currents of Ge MOSFETs are even less than that of Si MOSFETs. Moreover, the significant velocity overshoot also has been found in Ge MOSFETs.

Effect of dimensional expansion on carrier transport behaviors of the hexagonal Bi-based perovskite crystals

All-inorganic Cs_(3)Bi_(2)I_(9)(CBI)halide perovskites are sought to be candidate for photoelectrical materials because of their low toxicity and satisfactory stability.Unfortunately,the discrete molecular[Bi2I9]3−clusters limit the charge-transport behaviors.Herein,the defect halide perovskite based on trivalent Bi^(3+)is expanded to Cs_(3)Bi_(2)I_(6)Br_(3)(CBIB).Centimeter-size CBIB single crystal(Φ15×70 mm^(3))was grown by the vertical Bridgeman method.The powder X-ray diffraction analysis shows that CBIB has structure with lattice parameters of a=b=8.223Å,c=10.024Å,α=β=90°andγ=120°.The density functional theory(DFT)calculations demonstrate that the charge density distribution was enhanced after the dimensional expansion.The enhancement of carrier transport ability of(00l)in-plane is characterized before and after dimensional improvement.The obtained CBIB(001)exhibited an electron mobility up to 40.03 cm^(2)V^(−1)s^(−1)by time-of-flight(TOF)technique,higher than 26.46 cm^(2)V^(−1)s^(−1)of CBI(001).Furthermore,the X-ray sensitivity increases from 707.81μC Gy^(−1)cm^(−2)for CBI(001)to 3194.59μC Gy−1 cm^(−2)for CBIB(001).This research will deepen our understanding of Bi-based perovskite materials and afford more promising strategies for lead-free perovskite optoelectronic devices modification.

Direct Observation of Carrier Transportation Process in InGaAs/GaAs Multiple Quantum Wells Used for Solar Cells and Photodetectors

The resonant excitation is used to generate photo-excited carriers in quantum wells to observe the process of the carriers transportation by comparing the photoluminescence results between quantum wells with and without a p-n junction. It is observed directly in experiment that most of the photo-excited carriers in quantum wells with a p-n junction escape from quantum wells and form photoeurrent rather than relax to the ground state of the quantum wells. The photo absorption coei^cient of multiple quantum wells is also enhanced by a p-n junction. The results pave a novel way for solar cells and photodetectors making use of low-dimensional structure.

Carrier Transport Across Grain Boundaries in Polycrystalline Silicon Thin Film Transistors

We established a model for investigating polycrystalline silicon（poly-Si） thin film transistors（TFTs）.The effect of grain boundaries（GBs） on the transfer characteristics of TFT was analyzed by considering the number and the width of grain boundaries in the channel region,and the dominant transport mechanism of carrier across grain boundaries was subsequently determined.It is shown that the thermionic emission（TE） is dominant in the subthreshold operating region of TFT regardless of the number and the width of grain boundary.To a poly-Si TFT model with a 1 nm-width grain boundary,in the linear region,thermionic emission is similar to that of tunneling（TU）,however,with increasing grain boundary width and number,tunneling becomes dominant.

Carrier transport via V-shaped pits in InGaN/GaN MQW solar cells

Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.

Nonlinear magneto-mechanical-thermo coupling characteristic analysis for transport behaviors of carriers in composite multiferroic piezoelectric semiconductor nanoplates with surface effect

In this paper,to better reveal the surface effect and the screening effect as well as the nonlinear multi-field coupling characteristic of the multifunctional piezoelectric semiconductor(PS)nanodevice,and to further improve its working performance,a magneto-mechanical-thermo coupling theoretical model is theoretically established for the extensional analysis of a three-layered magneto-electro-semiconductor coupling laminated nanoplate with the surface effect.Next,by using the current theoretical model,some numerical analyses and discussion about the surface effect,the corresponding critical thickness of the nanoplate,and the distributions of the physical fields(including the electron concentration perturbation,the electric potential,the electric field,the average electric displacement,the effective polarization charge density,and the total charge density)under different initial state electron concentrations,as well as their active manipulation via some external magnetic field,pre-stress,and temperature stimuli,are performed.Utilizing the nonlinear multi-field coupling effect induced by inevitable external stimuli in the device operating environment,this paper not only provides theoretical support for understanding the size-dependent tuning/controlling of carrier transport as well as its screening effect,but also assists the design of a series of multiferroic PS nanodevices.

Pressure Effects on the Charge Carrier Transportation of BaF_2 Nanocrystals

The charge transport behavior of barium fluoride nanocrystals is investigated by in situ impedance measurement up to 35 GPa. It is found that the parameters change discontinuously at about 6.9 GPa, corresponding to the phase transition of BaF2 nanocrystals under high pressure. The charge carriers in BaF2 nanocrystals include both Fions and electrons. Pressure makes the electronic transport more difficult. The defects at grains dominate the electronic transport process. Pressure could make the charge-discharge processes in the Fm3m phase more difficult.

Multi-carrier transport in ZrTe_5 film

Single-layered zirconium pentatelluride （ZrTes） has been predicted to be a large-gap two-dimensional （2D） topolog- ical insulator, which has attracted particular attention in topological phase transitions and potential device applications. Herein, we investigated the transport properties in ZrTe5 films as a function of thickness, ranging from a few nm to several hundred nm. We determined that the temperature of the resistivity anomaly peak （Tp） tends to increase as the thickness decreases. Moreover, at a critical thickness of ~ 40 rim, the dominating carriers in the films change from n-type to p-type. A comprehensive investigation of Shubnikov-de Hass （SdH） oscillations and Hall resistance at variable temperatures revealed a multi-carrier transport tendency in the thin films. We determined the carrier densities and mobilities of two majority car- riers using the simplified two-carrier model. The electron carriers can be attributed to the Dirac band with a non-trivial Berry phase ~, while the hole carriers may originate from surface chemical reaction or unintentional doping during the microfabrication process. It is necessary to encapsulate the ZrTe5 film in an inert or vacuum environment to potentially achieve a substantial improvement in device quality.

Effect of transient space-charge perturbation on carrier transport in high-resistance CdZnTe semiconductor

The polarization effect introduced by electric field deformation is the most important bottleneck of CdZnTe detector in x-ray imaging. Currently, most of studies focus on electric field deformation caused by trapped carriers;the perturbation of electric field due to drifting carriers has been rarely reported. In this study, the effect of transient space-charge perturbation on carrier transport in a CdZnTe semiconductor is evaluated by using the laser-beam-induced current(LBIC) technique.Cusps appear in the current curves of CdZnTe detectors with different carrier transport performances under intense excitation, indicating the deformation of electric field. The current signals under different excitations are compared. The results suggest that with the increase of excitation, the amplitude of cusp increases and the electron transient time gradually decreases. The distortion in electric field is independent of carrier transport performance of detector. Transient space-charge perturbation is responsible for the pulse shape and affects the carrier transport process.

Measurement accuracy analysis of the free carrier absorption determination of the electronic transport properties of silicon wafers

By, introducing the random and systematic errors in simulated data computed from conventional frequency-scan and laterally resolved modulated free carrier absorption theory models, we investigate the relative determination sensitivities of three electronic transport properties, namely, carrier lifetime carrier diffusivity and front surface recombination velocity of silicon wafers determined by frequency-scan and laterally resolved techniques. The phase and amplitude data with random errors as functions of the modulation frequency at zero pump-probe-beam separation or of the two-beam separation at four different modulation frequencies are simultaneously fitted to an appreciated carrier diffusion model to extract three transport parameters. The statistical results and fitted accuracies of the transport parameter determined by both techniques are theoretically analysed. Corresponding experimental results are carried out to compare to the simulated results. The simulated and experimental results show that the determination of the transport properties of silicon wafers by the laterally resolved technique are more accurate, as compared with that by the frequency-scan technique.

A Pin gene families encoding components of auxin efflux carriers in Brassica juncea

Based on the sequence information of Arabidopsis PIN1, two cDNAs encoding PIN homologues fromBrassica juncea, Bjpin2 and Bjpin3, were isolated through cDNA library screening. Bjpin2 and Bjpin3encoded proteins containing 640 and 635 amino acid residues, respectively, which shared 97.5% identities witheach other and were highly homologous to Arabidopsis PIN1, PIN2 and other putative PIN proteins. BjPIN2and BjPIN3 had similar structures as AtPIN proteins. Northern blot analysis indicated that Bjpin2 wasexpressed in stem, leaf and floral tissues, while Bjpin3 was expressed predominantly in stem and hypocotyls.Two promoter fragments of pin genes, Bjpin-X and Bjpin-Z, were isolated by 'genome walking' techniqueusing primers at 5'-end of pin cDNA. Promoter-gus fusion studies revealed the GUS activities driven byBjpin-X were at internal side of xylem and petal; while those driven by Bjpin-Z were detected at leaf vein,epidermal cell and cortex of stem, vascular tissues and anther. Results of the pin genes with differentexpression patterns in B. juncea suggested the presence of a gene family.

Hepatocellular transport proteins and their role in liver disease

MOLECULAR PHYSIOLLGY OF HEPATOCELLULAR TRANSPORT PROTEINS Basolaferal transport systems Na+-dependent bile salt uptake Uptake of bile salts into the liver was first isolated perfused rat liver[1],isolated hepatocyte cultures and basolateral plasma membrane vesicles [2,4].

Isolation and functional analysis of a Brassica juncea gene encoding a com-ponent of auxin efflux carrier

Polar auxin transport plays a divergent role in plant growth and developmental processes including root and embryo development, vascular pattern formation and cell elongation. Recently isolated Arabidopsis pin gene family was believed to encode a component of auxin efflux carrier (G(?)lweiler et al, 1998). Based on the Arabidopsis pin1 sequence we have isolated a Brassica juncea cDNA (designated Bjpin1), which encoded a 70-kDa putative auxin efflux carrier. Deduced BjPIN1 shared 65% identities at protein level with AtPINl and was highly homologous to other putative PIN proteins of Arabidopsis (with highest homology to AtPIN3). Hydrophobic analysis showed similar structures between BjPINl and AtPIN proteins. Presence of 6 exons (varying in size between 65 bp and 1229 bp) and 5 introns (sizes between 89 bp and 463 bp) in the genomic fragment was revealed by comparing the genomic and cDNA sequences. Northern blot analysis indicated that Bjpin1 was expressed in most of the tissues tested, with a relatively higher level of transcript in flowers and a lower level in root tissues. Promoter-reporter gene fusion studies further revealed the expression of Bjpin1 in the mature pollen grains, young seeds, root tip, leaf vascular tissue and trace bundle, stem epidermis, cortex and vascular cells. BjPINl was localized on the plasma membrane as demonstrated through fusion expression of green fluorescent protein (GFP). Auxin efflux carrier activity was elevated in transgenic Arabidopsis expressing BjPIN1.

Dynamical study on charge injection and transport in a metal/polythiophene/metal structure

The dynamical process of charge injection from metal electrode to a nondegenerate polymer in a metal/polythiophene （PT）/metal structure has been investigated by using a nonadiabatic dynamic approach. It is found that the injected charges form wave packets due to the strong electron-lattice interaction in PT. We demonstrate that the dynamical formation of the wave packet sensitively depends on the strength of applied voltage, the electric field, and the contact between PT and electrode. At a strength of the electric field more than 3.0 × 10^4 V/cm, the carriers can be ejected from the PT into the right electrode. At an electric field more than 3.0 × 10^5 V/cm, the wave packet cannot form while it moves rapidly to the right PT/metal interface. It is shown that the ejected quantity of charge is noninteger.

Evaluation of effective carrier system and function on hydrocarbon accumulation in Gaoyou Sag,Subei Basin,China

Effective carrier system comprises carrier beds which transport hydrocarbons. The spatial and temporal effectiveness of carrier system is identified according to the relevance of hydrocarbon show, hydrocarbon inclusion and sealing ability of fault to hydrocarbons distribution, together with matching relation of activity history of fault and hydrocarbon generation history of source rock. On the basis of the above considerations, transporting ability of effective carrier system can be evaluated using parameters such as fluid potential, porosity and permeability, spatial coefficient of effective pathway as well as activity rate of fault. Additionally, a new concept of＂transporting threshold porosity＂ was proposed. Five styles of effective carrier systems were established in Gaoyou Sag, displaying either layered or zonal distribution characteristics, and transporting time ranges from the sedimentary time of Ezdz to early stage of sanduo uplift. Effective carrier systems can be described to be lowly-efficient and highly-efficient. Major faults （convex or steep fault plane） with activity rate greater than 20 m/Ma and structure ridges of sand layers with spatial coefficient of effective pathway greater than 25% are defined to be highly-efficient carrier beds. Hydrocarbons are concentrated around high-efficient carrier beds and E1 f traps of northern shanian area are predicted to have great potential.

The Physiological Mechanism of Postphloem Sugar Transport in Citrus Fruit

The dynamics of translocation and partitioning of 14C-phothsynthates, the concentration of sucrose in fruit tissues and the effects of the membrane carrier- and ATPase-specific inhibitors on 14C-sucrose uptake by juice sacs of the satsuma mandarin(Citrus unshiu Marc. cv. Miyagawa wase)fruit were examined at the stage of fruit enlargement and fruit full ripe. Kinetic data of 14C-photosynthate translocation indicated that the rate of photosynthate transport into juice sacs decreased with fruit maturation and sugar accumulation. Along the photosynthate translocation path, i. e. from vascular bundles to segment epidermis then to juice sacs, a descending sugar gradient was observed. With fruit maturation and sugar accumulation in juice sacs, the 14C photosynthate gradient increased, whereas the static sucrose concentration gradient decreased with fruit maturation and sugar accumulation. The higher gradient of specific 14C radioactivity was considered to favor diffusion and sugar transport into juice sacs at the later stage of fruit development. The rate of uptake 14C-sucrose by juice sacs of satsuma mandarin fruit was markedly reduced by PCMBS, EB, DNP and NO3-treatment. The above results suggested the participation of a carrier-mediated, energy-dependent sugar active transport process in juice sacs of satsuma mandarin fruit.

An effective strategy for cloning the mitochondrial citrate carrier: identification, characterization and tissue distribution in silver eel

A general and effective strategy to identify cDNA encoding for mitochondrial silver eel citrate carrier (CIC) has been developed. In particular using prim- ers directed towards the highly conserved signature motif of the ortholog citrate cDNA sequences, the full-length silver eel cDNA from liver was obtained. This is 1193 bp in length with 5’ and 3’ untranslated regions of 90 and 149 bp, respectively. The open rea- ding frame encodes a mature protein of 297 amino acids, preceded by a presequence of 20 amino acids. Additionally the mature CIC overexpressed in Es- cherichia coli and reconstituted into phospholipids vesicles showed the same substrate specificity of the native protein previously characterized in silver eel. The tissue distribution of silver eel CIC mRNAs was investigated and transcripts were detected at high levels in swim bladder whereas a weaker signal was found in brain, gill, intestine and liver.

Using the Hg_xMg_(1-x)Te ternary compound as a room temperature photodetector: The electronic structure, charge transport, and response function of the energetic electromagnetic radiation

In the present work, firstly, a first-principles study of the structural, electronic, and electron transport properties of the HgxMg1-xTe（HMT） ternary compound is performed using the ABINIT package and the results are compared with Cd0.9Zn0.1 Te（CZT） as a current room-temperature photodetector. Next, the response functions of Hg0.6Mg0.4Te and Cd0.9Zn0.1Te under electromagnetic irradiation with 0.05 Me V, 0.2 MeV, 0.661 MeV and 1.33 MeV energies are simulated by using the MCNP code. According to these simulations, the Hg0.6Mg0.4Te ternary compound is suggested as a good semiconductor photodetector for use at room temperature.