Unraveling the influence of interface defects on antimony trisulfide solar cells

Antimony trisulfide(Sb_(2)S_(3)) solar cells suffer from large open circuit voltage deficits due to their intrinsic defects which limit the power conversion efficiency.Thus,it is important to elucidate these defects’ origin and defects at the interface.Here,we discover that sulfide radical defects have a significant impact on the performance of Sb_(2)S_(3)solar cells.Moreover,it has been illustrated that these defects at the CdS/Sb_(2)S_(3)interface can be reduced by optimizing the deposition process.A trap distribution model is used to quantify the defect density at the CdS/Sb_(2)S_(3)interface.It shows that the interface defects can be reduced by24% by improving the deposition process.This work reveals the importance of interface defects and guides the future optimization of Sb_(2)S_(3)solar cells.

Effect of Defects at the Buffer Layer CdS/Absorber CIGS Interface on CIGS Solar Cell Performance

This scientific paper presents a study investigating the effects of defects at the CdS/CIGS and CdS/SDL interfaces on the performance of CIGS solar cells. The objective of this study is to analyze the influence of defects at the interface between the CdS buffer layer and the CIGS absorber, as well as the surface defect layer (SDL), on CIGS solar cell performance. The study explores three key aspects: the impact of the conduction band offset (CBO) at the CdS/CIGS interface, the effects of interface defects and defect density on performance, and the combined influence of CBO and defect density at the CdS/ SDL and SDL/CIGS interfaces. For interface defects not exceeding 1013 cm-2, we obtained a good efficiency of 22.9% when -0.1 eV analyzing the quality of CdS/SDL and SDL/CIGS junctions, it appears that defects at the SDL/CIGS interface have very little impact on the performances of the CIGS solar cell. By optimizing the electrical parameters of the CdS/SDL interface defects, we achieved a conversion efficiency of 23.1% when -0.05 eV < CBO < 0.05 eV.

Modulation on electrostatic potential to build a firm bridge at NiO_(x)/perovskite interface for efficient and stable perovskite solar cells

The NiO_(x)/perovskite interface in NiO_(x)-based inverted perovskite solar cells(PSCs)is one of the main issues that restrict device performance and long-term stability,as the unwanted interfacial defects and undesirable redox reactions cause severe interfacial non-radiative recombination and open-circuit voltage(Voc)loss.Herein,a series of self-assembled molecules(SAMs)are employed to bind,bridge,and stabilize the NiO_(x)/perovskite interface by regulating the electrostatic potential.Based on systematically theoretical and experimental studies,4-pyrazolecarboxylic acid(4-PCA)is proven as an efficient molecule to simultaneously passivate the NiO_(x)and perovskite surface traps,release the interfacial tensile stress as well as quench the detrimental interface redox reactions,thus effectively suppressing the interfacial non-radiative recombination and enhancing the quality of perovskite crystals.Consequently,the PSCs with 4-PCA treatment exhibited an eminently increased Voc,leading to a significant increase in power conversion efficiency from 21.28%to 23.77%.Furthermore,the unencapsulated devices maintain 92.6%and 81.3%of their initial PCEs after storing in air with a relative humidity of 20%–30%for 1000 h and heating at 65℃for 500 h in a N_(2)-filled glovebox,respectively.

First-principles study of non-radiative carrier capture by defects at amorphous-SiO_(2)/Si(100)interface

Defects have a significant impact on the performance of semiconductor devices.Using the first-principles combined with one-dimensional static coupling theory approach,we have calculated the variation of carrier capture coefficients with temperature for the interfacial defects P_(b0) and P_(b1) in amorphous-SiO_(2)/Si(100)interface.It is found that the geometrical shapes of P_(b0) and P_(b1) defects undergo large deformations after capturing carriers to form charged defects,especially for the Si atoms containing a dangling bond.The hole capture coefficients of neutral P_(b0) and P_(b1) defects are largest than the other capture coefficients,indicating that these defects have a higher probability of forming positively charged centres.Meanwhile,the calculated results of non-radiative recombination coefficient of these defects show that both P_(b0) and P_(b1) defects are the dominant non-radiative recombination centers in the interface of a-SiO_(2)/Si(100).

Passivation of carbon dimer defects in amorphous SiO_2/4H–SiC(0001) interface:A first-principles study

An amorphous SiO2/4 H–Si C（0001） interface model with carbon dimer defects is established based on density functional theory of the first-principle plane wave pseudopotential method.The structures of carbon dimer defects after passivation by H2 and NO molecules are established,and the interface states before and after passivation are calculated by the Heyd–Scuseria–Ernzerhof（HSE06） hybrid functional scheme.Calculation results indicate that H2 can be adsorbed on the O2–C = C–O2 defect and the carbon–carbon double bond is converted into a single bond.However,H2 cannot be adsorbed on the O2–（C = C）′ –O2 defect.The NO molecules can be bonded by N and C atoms to transform the carbon–carbon double bonds,thereby passivating the two defects.This study shows that the mechanism for the passivation of Si O2/4 H–SiC（0001） interface carbon dimer defects is to convert the carbon–carbon double bonds into carbon dimers.Moreover,some intermediate structures that can be introduced into the interface state in the band gap should be avoided.

Contribution of Surface Defects to the Interface Conductivity of SrTiO_3/LaAlO_3

Based on the first-principles method, the structural stability and the contribution of point defects such as O, Sr or Ti vacancies on two-dimensional electron gas of n- and p-type LaAlO3/SrTiO3 interfaces are investigated. The results show that O vacancies at p-type interfaces have much lower formation energies, and Sr or Ti vacancies at n-type interfaces are more stable than the ones at p-type interfaces under O-rich conditions. The calculated densities of states indicate that O vacancies act as donors and give a significant compensation to hole carriers, resulting in insulating behavior at p-type interfaces. In contrast, Sr or Ti vacancies tend to trap electrons and behave as acceptors. Sr vacancies are the most stable defects at high oxygen partial pressures, and the Sr vacancies rather than Ti vacancies are responsible for the insulator-metal transition of n-type interface. The calculated results can be helpful to understand the tuned electronic properties of LaAlO3 /SrTiO3 heterointerfaces.

Improvement in IBC-silicon solar cell performance by insertion of highly doped crystalline layer at heterojunction interfaces

By inserting a thin highly doped crystalline silicon layer between the base region and amorphous silicon layer in an interdigitated back-contact （IBC） silicon solar cell, a new passivation layer is investigated. The passivation layer performance is characterized by numerical simulations. Moreover, the dependence of the output parameters of the solar cell on the additional layer parameters （doping concentration and thickness） is studied. By optimizing the additional passivation layer in terms of doping concentration and thickness, the power conversion efficiency could be improved by a factor of 2.5%, open circuit voltage is increased by 30 mV and the fill factor of the solar cell by 7.4%. The performance enhancement is achieved due to the decrease of recombination rate, a decrease in solar cell resistivity and improvement of field effect passivation at heterojunction interface. The above-mentioned results are compared with reported results of the same conventional interdigitated back-contact silicon solar cell structure. Furthermore, the effect of a-Si：H/c-Si interface defect density on IBC silicon solar cell parameters with a new passivation layer is studied. The additional passivation layer also reduces the sensitivity of output parameter of solar cell to interface defect density.

Interface of quasicrystal and crystal

A model on the coexisting phase of quasicrystal-crystal is proposed, with which we concretely investigate the inter- face effects for coexisting phases of one-dimensional orthorhombic quasicrystal-isotropic crystal and three-dimensional icosahedral quasierystal-cubic crystal. The phason strain fields which play an important role in some processes are determined. Some factors affecting the strain fields, e.g., the material constants of phonon, phason, phonon-phason coupling of the quasicrystal and the elastic modulus and the size of the crystal are also explored.

Heat transport in low-dimensional materials: A review and perspective

Heat transport is a key energetic process in materials and devices. The reduced sample size, low dimension of the problem and the rich spectrum of material imperfections introduce fruitful phenomena at nanoscale. In this review, we summarize recent progresses in the understanding of heat transport process in low-dimensional materials, with focus on the roles of defects, disorder, interfaces, and the quantum- mechanical effect. New physics uncovered from computational simulations, experimental studies, and predictable models will be reviewed, followed by a perspective on open challenges.

Tunable and improved microwave absorption of flower-like core@shell MFe_(2)O_(4)@MoS_(2)(M=Mn,Ni and Zn)nanocomposites by defect and interface engineering

Previous results revealed that the defect and/or interface had a great impact on the electromagnetic pa-rameters of materials.In order to understand the main physical mechanisms and effectively utilize these strategies,in this study,M Fe_(2)O_(4)and flower-like core@shell M Fe_(2)O_(4)@MoS_(2)(M=Mn,Ni,and Zn)sam-ples with different categories were elaborately designed and selectively produced in large scale through a simple two-step hydrothermal reaction.We conducted the systematical investigation on their microstruc-tures,electromagnetic parameters and microwave absorption performances(MAPs).The obtained results revealed that the large radius of M^(2+)cation could effectively boost the concentration of oxygen vacancy in the M Fe_(2)O_(4)and M Fe_(2)O_(4)@MoS_(2)samples,which resulted in the improvement of dielectric loss capabil-ities and MAPs.Furthermore,the introduction of MoS_(2)nanosheets greatly improved the interfacial effect and enhanced the polarization loss capabilities,which also boosted the MAPs.By taking full advantage of the defect and interface,the designed M Fe_(2)O_(4)@MoS_(2)samples displayed tunable and excellent com-prehensive MAPs including strong absorption capability,wide absorption bandwidth and thin matching thicknesses.Therefore,the clear understanding of defect and interface engineering made these strategies well elaborately designed and applicable to improving MAPs.

A DOMINANT DEFECT AT THE Si/SiO_2 INTERFACE IN MOS STRUCTURE

The interface defects at the Si/SiO_2 interface in ρ-type silicon (111) MOS structures have been studied by the DLTS method. A dominant defect H_(it),(0.503) at the Si/SiO_2 interface has been found. Its characteristics are (i) the average hole ionization Gibbs free energy △G_p≥0.503 eV; (ii) by changing the gate bias when the distance from Fermi level to the top of Si valence band at the Si/SiO_2 interface is less than △G_p there is still the strong DLTS peak; (iii) its hole apparent activation energy increases with the dectease of the height of semiconductor surface potential barrier; and (iv) its hole capture process causes the multiexponential capacitance transience as a function of pulse width and the H_(it)(0.503) level are very difficult to be fully filled with the holes introduced by thepulst with alimited width. All above show that there is a continuous transition energy band between the energy bands of the covalent crystal silicon and the SiO_2 in the Si/SiO_2 systems formed by thermal oxidation; the dominant defect H_(it)(0.503) is distributed in the transition region, and the distance of H_(it)(0.503) level from the top of the valence band increases with the distance from the silicon surface.

Defect and interface engineering in core@shell structure hollow carbon@MoS_(2)nanocomposites for boosted microwave absorption performance

Defect and interface engineering are efficient approaches to adjust the physical and chemical properties of nanomaterials.In order to effectively utilize these strategies for the improvement of microwave absorption properties(MAPs),in this study,we reported the synthesis of hollow carbon shells and hollow carbon@MoS_(2)nanocomposites by the template-etching and templateetching-hydrothermal methods,respectively.The obtained results indicated that the degree of defect for hollow carbon shells and hollow carbon@MoS_(2)could be modulated by the thickness of hollow carbon shell,which effectively fulfilled the optimization of electromagnetic parameters and improvement of MAPs.Furthermore,the microstructure investigations revealed that the precursor of hollow carbon shells was encapsulated by the sheet-like MoS_(2)in high efficiency.And the introduction of MoS_(2)nanosheets acting as the shell effectively improved the interfacial effects and boosted the polarization loss capabilities,which resulted in the improvement of comprehensive MAPs.The elaborately designed hollow carbon@MoS_(2)samples displayed very outstanding MAPs including strong absorption capabilities,broad absorption bandwidth,and thin matching thicknesses.Therefore,this work provided a viable strategy to improve the MAPs of microwave absorbers by taking full advantage of their defect and interface engineering.

Investigation of an a-Si/c-Si interface on a c-Si(P) substrate by simulation

We investigate the recombination mechanism in an a-Si/c-Si interface,and analyze the key factors that influence the interface passivation quality,such as Q_s,δ_p/δ_n and D_（it）.The polarity of the dielectric film is very important to the illustration level dependent passivation quality;when nδ_n = pδ_p and the defect level E_t equal to E_i（c-Si）,the defect states are the most effective recombination center,AFORS-HET simulation and analysis indicate that emitter doping and a-Si/c-Si band offset modulation are effective in depleting or accumulating one charged carrier.Interface states（D_（it）） severely deteriorate V_（oc） compared with J_（sc） for a-Si/c-Si HJ cell performance when D_（it） is over 1×10^（10） cm^（-2）·eV^（-1）.For a c-Si（P）/a-Si（P~＋） structure,φ_（BSF） in c-Si andφ_0 in a-Si have different performances in optimization contact resistance and c-Si（P）/a-Si（P~＋） interface recombination.

Self-supported transition metal chalcogenides for oxygen evolution

Owing to stable spatial framework and large electrochemical interface,self-supported transition metal chalcogenides have been actively explored in renewable energy fields,especially in oxygen evolution reaction(OER).Here,we review the research progress of self-supported transition metal chalcogenides(including sulfides,selenides,and tellurides)for the OER in recent years.The basic principle and evaluation parameters of OER are first introduced,and then the preparation methods of transition metal chalcogenides on various self-supporting substrates(including Ni foam(NF),carbon cloth(CC),carbon fiber paper(CFP),metal mesh/plate,etc.)are systematically summarized.Subsequently,advanced optimization strategies(including interface and defect engineering,heteroatom doping,edge engineering,surface morphology engineering,and construction of heterostructure)are introduced in detail to improve the inherent catalytic activity of self-supported electrocatalysts.Finally,the challenges and prospects of developing more promising self-supported chalcogenide electrocatalysts are proposed.

Anion regulating endows core@shell structured hollow carbon spheres@MoSxSe_(2−x)with tunable and boosted microwave absorption performance

Due to the good manipulation of electronic structure and defect,anion regulating should be a promising strategy to regulate the electromagnetic(EM)parameters and optimize the EM wave absorption performances(EMWAPs).In this work,we proposed a facile route for the large-scale production of core@shell structured hollow carbon spheres@MoSxSe_(2−x)(x=0.2,0.6,and 1.0)multicomponent nanocomposites(MCNCs)through a mild template method followed by hydrothermal process.The obtained results revealed that the designed hollow carbon spheres@MoSxSe_(2−x)MCNCs presented the improved sulfur vacancy concentration by regulating the x value from 0.2 to 1.0.The obtained hollow carbon spheres@MoSxSe_(2−x)MCNCs displayed the extraordinary comprehensive EMWAPs because of the introduced abundant defects and excellent interfacial effects.Furthermore,the as-prepared hollow carbon spheres@MoSxSe_(2−x)MCNCs presented the progressively improved comprehensive EMWAPs with the x value increasing from 0.2 to 1.0,which could be explained by their boosted polarization loss abilities and impedance matching characteristics originating from the enhanced sulfur vacancy concentration.Therefore,our findings not only demonstrated that the anion regulating was a promising method to optimize EM parameters and EMWAPs,but also provided a facile route to design the transition metal dichalcogenides-based MCNCs as the much more attractive candidates for highperformance microwave absorbers.