Advances in CIGS thin film solar cells with emphasis on the alkali element post-deposition treatment

In the past tens of years,the power conversion efficiency of Cu(In,Ga)Se2(CIGS)has continuously improved and been one of the fastest growing photovoltaic technologies that can also help us achieve the goal of carbon emissions reduction.Among several key advances,the alkali element post-deposition treatment(AlK PDT)is regarded as the most important finding in the last 10 years,which has led to the improvement of CIGS solar cell efficiency from 20.4%to 23.35%.A profound understanding of the influence of alkali element on the chemical and electrical properties of the CIGS absorber along with the underlying mechanisms is of great importance.In this review,we summarize the strategies of the alkali element doping in CIGS solar cell,the problems to be noted in the PDT process,the effects on the CdS buffer layer,the effects of different alkali elements on the structure and morphology of the CIGS absorber layer,and retrospect the progress in the CIGS solar cell with emphasis on the alkali element post deposition treatment.

A brief review of formation energies calculation of surfaces and edges in semiconductors

To have a high quality experimental growth of crystals, understanding the equilibrium crystal shape(ECS) in different thermodynamic growth conditions is important. The factor governing the ECS is usually the absolute surface formation energies for surfaces(or edges in 2D) in different orientations. Therefore, it is necessary to obtain an accurate value of these energies in order to give a good explanation for the observation in growth experiment. Historically, there have been different approaches proposed to solve this problem. This paper is going to review these representative literatures and discuss the pitfalls and advantages of different methods.

Molecular Properties of the Epstein-Barr virus BFRF3 Gene

We report the results of cloning,expression,subcellular localization analysis,and molecular properties of the Epstein-Barr virus （EBV） BFRF3 gene,using several bioinformatics tools.Bioinformatics analysis indicated that the encoding protein of EBV BFRF3 gene （designated BFRF3） has a conserved Herpes_capsid domain,which was found to be closely related to the gammaherpesvirus capsid protein family,and is highly conserved among its counterparts.

Defects properties and vacancy diffusion in Cu_(2)MgSnS_(4)

Cu_(2)Mg_(Sn)S_(4)(CZTS)is a promising photovoltaic absorber material,however,efficiency is largely hindered by potential fluctuation and a band tailing problem due to the abundance of defect complexes and low formation energy of an intrinsic Cu_(Zn)defect.Alternatives to CZTS by group I,II,or IV element replacement to circumvent this challenge has grown research in-terest.In this work,using a hybrid(HSE06)functional,we demonstrated the qualitative similarity of defect thermodynamics and electronic properties in Cu_(2)Mg_(Sn)S_(4)(CMTS)to CZTS.We show Sn_(Mg)to be abundant when in Sn-and Cu-rich condition,which can be detrimental,while defect properties are largely similar to CZTS in Sn-and Cu-poor.Under Sn-and Cu-poor chemic-al potential,there is a general increase in formation energy in most defects except Sn_(Mg),Cu_(Mg)remains as the main contribu-tion to p-type carriers,and Sn_(Mg)may be detrimental because of a deep defect level in the mid gap and the possibility of form-ing defect complex Sn_(Mg)+Mg_(Sn).Vacancy diffusion is studied using generalized gradient approximation,and we find similar va-cancy diffusion properties for Cu vacancy and lower diffusion barrier for Mg vacancy,which may reduce possible Cu-Mg dis-order in CMTS.These findings further confirm the feasibility of CMTS as an alternative absorber material to CZTS and suggest the possibility for tuning defect properties of CZTS,which is crucial for high photovoltaic performance.

Direct or indirect band gap

The direct or indirect nature to the bandgap of a semiconductor is a fundamental property.Despite the extensive research and broad applications of the conventional semiconductors,the understanding of the mechanisms determining their direct or indirect nature to the bandgap remains a challenge.Lack of fundamental understanding of the mechanism controlling the indirect bandgap nature of Si might be the main reason for the difficulty of developing Si-based direct bandgap materials.

Stable Intrinsic Long Range Antiferromagnetic Coupling in Dilutely V Doped Chalcopyrite

A stable and long-range antiferromagnetic(AFM)coupling without charge carrier mediators has been searched for a long time,but the existence of this kind of coupling is still lacking.Based on first principle calculations,we systematically study carrier free long-range AFM coupling in four transition metal chalcopyrite systems:ABTe2(A=Cu or Ag,B=Ga or In)in the dilute doping case.The AFM coupling is mainly due to the p-d coupling and electron redistribution along the interacting chains.The relatively small energy difference between p and d orbitals,as well as between dopants and atoms in the middle of the chain can enhance the stability of longrange AFM configurations.A multi-band Hubbard model is proposed to provide fundamental understanding of long-range AFM coupling.

Supplementary Material: Stepping Stone Mechanism: Carrier-Free Long-Range Magnetism Mediated by Magnetized Cation States in Quintuple Layer

The long-range magnetism observed in group-V tellurides quintuple layers is the only working example of carrierfree dilute magnetic semiconductors(DMS),whereas the physical mechanism is unclear,except the speculation on the band topology enhanced van Vleck paramagnetism.Based on DFT calculations,we find a stable longrange ferromagnetic order in a single quintuple layer of Cr-doped Bi_(2)Te_(3) or Sb_(2)Te_(3),with the dopant separation more than 9?.This configuration is the global energy minimum among all configurations.Different from the conventional super exchange theory,the magnetism is facilitated by the lone pair derived anti-bonding states near the cations.Such anti-bonding states work as stepping stones merged in the electron sea and conduct magnetism.Further,spin orbit coupling induced band inversion is found to be insignificant in the magnetism.Therefore,our findings directly dismiss the common misbelief that band topology is the only factor that enhances the magnetism.We further demonstrate that removal of the lone pair derived states destroys the long-range magnetism.This novel mechanism sheds light on the fundamental understanding of long-range magnetism and may lead to discoveries of new classes of DMS.

stAPAminer:Mining Spatial Patterns of Alternative Polyadenylation for Spatially Resolved Transcriptomic Studies

Alternative polyadenylation(APA)contributes to transcriptome complexity and gene expression regulation and has been implicated in various cellular processes and diseases.Singlecell RNA sequencing(scRNA-seq)has enabled the profiling of APA at the single-cell level;however,the spatial information of cells is not preserved in scRNA-seq.Alternatively,spatial transcriptomics(ST)technologies provide opportunities to decipher the spatial context of the transcriptomic landscape.Pioneering studies have revealed potential spatially variable genes and/or splice isoforms;however,the pattern of APA usage in spatial contexts remains unappreciated.In this study,we developed a toolkit called stAPAminer for mining spatial patterns of APA from spatially barcoded ST data.APA sites were identified and quantified from the ST data.In particular,an imputation model based on the k-nearest neighbors algorithm was designed to recover APA signals,and then APA genes with spatial patterns of APA usage variation were identified.By analyzing wellestablished ST data of the mouse olfactory bulb(MOB),we presented a detailed view of spatial APA usage across morphological layers of the MOB.We compiled a comprehensive list of genes with spatial APA dynamics and obtained several major spatial expression patterns that represent spatial APA dynamics in different morphological layers.By extending this analysis to two additional replicates of the MOB ST data,we observed that the spatial APA patterns of several genes were reproducible among replicates.stAPAminer employs the power of ST to explore the transcriptional atlas of spatial APA patterns with spatial resolution.This toolkit is available at https://github.com/BMILAB/stAPAminer and https://ngdc.cncb.ac.cn/biocode/tools/BT007320.

近年来加泰罗尼亚分离主义运动活跃的动因及走向分析

近年来,由于西班牙经济危机的催化作用、拉霍伊政府加强中央集权的刺激作用、加泰罗尼亚分离主义政治势力的得势、欧洲分离主义运动猖獗等多重因素导致了加泰罗尼亚分离主义运动走向了活跃。由于西班牙的坚决反对,欧盟、美国的不支持,加泰罗尼亚很难在短期内实现分离,其分离问题也很难在短期内得以彻底解决。

Riemann-Hilbert approach to TD equation with nonzero boundary condition

We extend the Riemann-Hilbert approach to the TD equation, which is a highly nonlinear differential integrable equation. Zero boundary condition at infinity for the TD equation is not suitable. Inverse scattering transform for this equation involves the singular Riemann-Hilbert problem, which means that the sectionally analytic functions have singularities on the boundary curve. Regularization procedures of the singular Riemann-Hilbert problem for two cases, the general case and the case for refiectionless potentials, are considered. Solitonic solutions to the TD equation are given.

A brief review of co-doping

Dopants and defects are important in semiconductor and magnetic devices. Strategies for controlling doping and defects have been the focus of semiconductor physics research during the past decades and remain critical even today. Co-doping is a promising strategy that can be used for effectively tuning the dopant populations, electronic properties, and magnetic properties. It can enhance the solubility of dopants and improve the stability of desired defects. During the past 20 years, significant experimental and theoretical efforts have been devoted to studying the characteristics of co-doping. In this article, we first review the historical development of co-doping. Then, we review a variety of research performed on co-doping, based on the compensating nature of co-dopants. Finally, we review the effects of contamination and surfactants that can explain the general mechanisms of co-doping.

Spectral analysis of generalized Volterra equation

A generalized Volterra lattice with a nonzero boundary condition is considered by virtue of the inverse scattering transform.The two-sheeted Riemann surface associated with the boundary problem is transformed into the Riemann sphere by introducing a suitable variable transformation.The associated spectral properties of the lattice in single-valued variable was discussed.The constraint condition about the nonzero boundary condition and the scattering data is found.

Forced(2+1)-dimensional discrete three-wave equation

We generalize the■-dressing method to investigate a(2+1)-dimensional lattice,which can be regarded as a forced(2+1)-dimensional discrete three-wave equation.The soliton solutions to the(2+1)-dimensional lattice are given through constructing different symmetry conditions.The asymptotic analysis of one-soliton solution is discussed.For the soliton solution,the forces are zero.