Two‑Dimensional Metal Halides for X‑Ray Detection Applications

Metal halide perovskites have recently emerged as promising candidates for the next generation of X-ray detectors due to their excellent optoelectronic properties.Especially,two-dimensional(2D)perovskites afford many distinct properties,including remarkable structural diversity,high generation energy,and balanced large exciton binding energy.With the advantages of 2D materials and perovskites,it successfully reduces the decomposition and phase transition of perovskite and effectively suppresses ion migration.Meanwhile,the existence of a high hydrophobic spacer can block water molecules,thus making 2D perovskite obtain excellent stability.All of these advantages have attracted much attention in the field of X-ray detection.This review introduces the classification of 2D halide perovskites,summarizes the synthesis technology and performance characteristics of 2D perovskite X-ray direct detector,and briefly discusses the application of 2D perovskite in scintillators.Finally,this review also emphasizes the key challenges faced by 2D perovskite X-ray detectors in practical application and presents our views on its future development.

Dimensionality regulation in tin halide perovskite solar cells: Toward high performance and stability

Tin halide perovskites(THPs)have received extensive attention due to their low toxicity and excellent optoelectronic properties,and are considered to be the most promising alternatives to develop efficient lead-free perovskite solar cells.However,due to the unique and inherent characteristics of Sn^(2+)being easily oxidized to Sn^(4+)and fast crystallization,tin perovskite solar cells(TPSCs)show relatively poor performance and stability,compared to the lead counterparts.Recently,the introduction of bulky organic spacers into three-dimensional(3D)THPs for dimensional regulation can not only prevent the intrusion of water and oxygen,but also inhibit the self-doping effect and ion migration.In this review,we will detail how dimensional regulation enables TPSCs with high performance and superior stability.First,we summarize the intrinsic properties of THPs and analyze the root causes of their poor performance and instability.Next,we discuss the specific structure and types of the dimensional regulation strategy.Then,the mechanism of dimensional regulation is discussed in detail,mainly from inhibiting the Sn^(2+)oxidation,optimizing crystallization,passivating defects,and improving energy level alignment.Finally,future challenges and prospects for dimensional regulation are elaborated to help researchers develop more efficient and stable TPSCs.

A chlorinated copolymer donor demonstrates a 18.13% power conversion efficiency

The rapid development of low-bandgap(LBG)nonfullerene acceptors and wide-bandgap(WBG)copolymer donors in recent years has boosted the power conversion efficiency(PCE)of organic solar cells(OSCs)to the 18%level[1−21].The commercialization of OSCs is highly expected.However,critical issues like the cost and the stability also determine whether OSCs can enter the market or not[22].

Flexible perovskite solar cells based on green,continuous roll-to-roll printing technology

By designing and fabricating thin film electronic devices on a flexible substrate instead of more commonly used rigid substrate, flexible electronics produced has opened a field of special applications. In this article, we first reviewed available products that may be used as flexible substrates, their characteristics and unique advantages as supporting material for flexible electronic devices. Secondly, flexible perovskite solar cell is examined in detail, with special focus on its potential large-scale fabrication processes. In particular, a comprehensive review is provided on low cost solution printing techniques that is viewed highly as a viable tool for potential commercialization of the perovskite solar cells. Furthermore, a summary is given on green processing for the solution printing production of flexible perovskite devices.

纤维素纳米晶须及其水凝胶的研究进展

纤维素是自然界中产量最大的天然高分子之一,因具有优良的性能、低廉的成本、且可再生循环等优点被广泛应用。天然纤维素通过特定方法处理得到的纤维素纳米晶须(CNCs)及其改性共聚物为原料制备的水凝胶因具有更加优良的力学性能、生物相容性、天然可降解性及丰富的来源等特点,近年来颇受科学家的关注。文中简要介绍了纤维素的结构、性质及CNCs的制备方法,综述了以CNCs及其改性共聚物为原料合成水凝胶的方法、性能表征和应用潜能的研究进展。

Development and Evaluation of a Loop-mediated Isothermal Amplification Assay for the Rapid Detection and Identification of Pectobacterium carotovorum on Celery in the Field

Pectobacterium carotovorum is the causal agent of bacterial soft rot in a wide range of vegetable host species.Once P.carotovorum infects the plant,the spread of the disease is difficult to control.In this study,a rapid and sensitive method based on loop-mediated isothermal amplification(LAMP)was developed for detecting P.carotovorum in celery with soft rot using a primer set designed from the pmrA conserved sequence of P.carotovorum.The specificity of the LAMP primer set for P.carotovorum was extensively validated on both P.carotovorum strains and nontarget strains.The sensitivity was 1 pg of P.carotovorum genomic DNA,which demonstrated 10 times more sensitive than the conventional PCR assay.LAMP was also used to detect P.carotovorum in bacterial suspension.The lowest detection concentration was 104 CFU·mL^−1.In addition,a LAMP assay,in conjunction with a crude DNA extraction method,was successfully performed on P.carotovorum-infected samples derived from both artificially and naturally infected plants.In summary,the LAMP assay established in this study constitutes a simple,sensitive,and rapid method for the detection of P.carotovorum,and has potential application in the control of celery soft rot disease through early detection.

Intermediates transformation for efficient perovskite solar cells

Perovskite materials have made a great progress in terms of the power conversion efficiency(PCE), rising from 3.8% to 25.2%. To obtain pinhole-free, superior crystal, and high-quality perovskite films with less defect, intermediates transformation is important, which has been clearly studied and widely applied.In this review, we systematically summarize the commonly formed intermediates and detailedly analyze their mechanisms from five aspects:(1) Solvent-induced intermediate;(2) HI-induced intermediate;(3)CH3NH2-induced intermediate;(4) MAAc-induced intermediate;(5) other intermediates. Finally, we also provide some prospects on high-quality perovskite fabrication based on using intermediates prudently.

Suppressed light-induced phase transition of CsPbBr_(2)I: Strategies, progress and applications in the photovoltaic field

The rapid rise in the power conversion efficiency(PCE)of CsPbBr_(2)I-based perovskite solar cells(PSCs),from 4.7%in 2016 to 11.08%in 2020,render it a promising material for use in photovoltaic devices.However,the phase stability and current hysteresis caused by photo-induced phase segregation in CsPbBr_(2)I represent major obstacles to further improvements in the PCE for such devices.In this review,we describe the basic structure and optical properties of CsPbBr_(2)I,and systematically elaborate on the mechanism of the phase transition.We then discuss the strategies in progress to suppress phase transition in CsPbBr_(2)I,and their potential application in the photovoltaic field.Finally,challenges and application prospects for CsPbBr2I PSCs are summarized in the final section of this article.

Strategies from small-area to scalable fabrication for perovskite solar cells

Recently,perovskite solar cells(PSCs) have flourished,and their power conversion efficiency(PCE) has increased from the initial 3.8% to 25.2% in 2019,which is an unprecedented advance.However,usually high-efficiency and stable PSCs are small-area devices prepared by spin coating.This method is not suitable for the preparation of large-area devices in commercialization.Therefore,there is an urgent need to develop new materials and methods for the scalable fabrication of PSCs.In this review,we first describe the common small-area PSCs preparation methods,understand the nucleation and crystal growth kinetics of perovskite,and analyze the reasons that hinder the development of small-area devices to large-area devices.Next,in order to meet the challenges of PSC’s scalable fabrication,we summarize and analyze four strategies:scaling up precursor solutions,scalable deposition methods for large-area films,scaling up charge-transport layers and back electrodes,developing solar modules.Finally,challenges and prospects are proposed to help researchers prepare high-efficiency large-area PSCs.

HI hydrolysis-derived intermediate as booster for CsPbI3 perovskite: from crystal structure, film fabrication to device performance

Nowadays,inorganic CsPbI3 perovskite solar cells(PSCs)have become one of the most attractive research hotspots in photovoltaic field for its superior chemical stability and excellent photo-electronic properties.Since the first independent report in 2015,the power conversion efficiency(PCE)of CsPbI3 based PSCs has sharply increased from 3.9%to 19.03%.Importantly,during the developing process of CsPbI3 PSCs,HI hydrolysis-derived intermediate plays an important role:from stabilizing the crystal structure,optimizing the fabricated film to boosting the device performance.In this review,the different crystal and electronic structures of CsPbI3 are introduced.We then trace the history and disputes of HI hydrolysis-derived intermediate to make this review more logical.Meanwhile,we highlight the functions of HI hydrolysis-derived intermediate,and systematically summarize the advanced works on CsPbI3 PSCs.Finally,the bottlenecks and prospects are revealed to further increase the CsPbI3 PSCs performance.

Unveiling the origin of performance enhancement of photovoltaic devices by upconversion nanoparticles

To better utilize the infrared(IR)region in sunlight for photovoltaic devices(PVs),upconversion nanoparticles(UCNPs)have been proposed to improve power conversion efficiency(PCE).However,researchers recently have found that the upconversion(UC)effect is negligible in PVs performance improvement for their ultra-low UC photoluminescence quantum yields of UCNPs solid film,while the real mechanism of UCNPs in PVs has not been clearly studied.Herein,based on the material inorganic perovskitesγ-CsPbI_(3),NaYF_(4):20%Yb^(3+),2%Er^(3+)UCNPs were integrated into different transport layer to optimize device performance.Compared with reference device,the short-circuit current density and PCE of optimized device reached 20.87 mA/cm^(2)(20.39 mA/cm^(2))and 18.34%(17.72%),respectively,without sacrificing open-circuit voltage and filling factor.Further experimental characterizations verified that the improved performance was attributable to enhanced visible light absorption instead of IR.To theoretically explain the statement,the light field distribution in device was simulated and the absorption in different layers was calculated.The results revealed that the introduction of UCNPs with different refractive index from other layers caused light field disturbance,and improved visible light captured by γ-CsPbI_(3).Importantly,through experiments and theoretical calculation,the research deeply explored the potential mechanism of UCNPs in optimizing PVs performance.

Advances in perovskite quantum-dot solar cells

Perovskite quantum-dots (PQDs) have emerged as prominent candidates for intriguing photovoltaic application due to their superior optoelectronic properties such as multiple exciton generation, bandgap tunability, electronic and surface chemistry properties, as well as flexible composition [1–5].

Perovskite films with gradient bandgap for self-powered multiband photodetectors and spectrometers

Bandgap-graded materials present varying spectral responses at different positions,making them possible to be used as an alternative to photoactive materials array in multi-spectral responsive devices,thus miniaturizing the apparatus.However,the preparation of bandgap-graded materials usually requires complicated deposition process.Here we report a facile lowtemperature solution process to make films with lateral bandgap gradients,which form spontaneously via self-spreading and interdiffusion of solutions.We show lead halide perovskite films with MAPbCl_(3)-MAPbBr_(3)and MAPbBr_(3)-MAPbI_(3)gradients,which exhibit light absorption onsets ranging from 410 to 781 nm.The bandgap-graded films were used to make self-powered multiband photodetectors,which show different spectral responses at different positions without applying bias voltage.Furthermore,self-powered spectrometers were made by using the multiband photodetectors.

有机太阳电池关键材料研究进展

有机太阳电池具有质量轻、柔性、印刷制备等优点,有巨大的应用潜力,从其诞生那一刻起便引起了学术界和工业界的广泛研究兴趣.历经25年的发展,有机太阳电池效率已突破18%,其快速进步得益于不断涌现的高性能新材料和器件制备技术,以及对电池活性层形貌、分子堆积和器件机理的深入理解.基于有机共轭结构的电子给体和电子受体材料是决定有机太阳电池性能的关键材料.本文将以给、受体材料的发展历程为主线,聚焦那些明星材料和里程碑工作,阐述高性能关键材料的分子结构演变和进化过程,最后展望其面临的挑战和未来发展方向.

Progress of the key materials for organic solar cells

Organic solar cells have attracted academic and industrial interests due to the advantages like lightweight,flexibility and roll-to-roll fabrication.Nowadays,18%power conversion efficiency has been achieved in the state-of-the-art organic solar cells.The recent rapid progress in organic solar cells relies on the continuously emerging new materials and device fabrication technologies,and the deep understanding on film morphology,molecular packing and device physics.Donor and acceptor materials are the key materials for organic solar cells since they determine the device performance.The past 25 years have witnessed an odyssey in developing high-performance donors and acceptors.In this review,we focus on those star materials and milestone work,and introduce the molecular structure evolution of key materials.These key materials include homopolymer donors,D-A copolymer donors,A-D-A small molecular donors,fullerene acceptors and nonfullerene acceptors.At last,we outlook the challenges and very important directions in key materials development.

厚膜有机太阳电池效率突破16%

近年来有机太阳电池效率突飞猛进,单结电池效率已经突破18%,然而这些高效率电池的活性层厚度通常只有100 nm左右,随着厚度增加,电池效率下降明显.为了实现有机太阳电池的产业化,发展对厚度不敏感,且可适用于卷对卷印刷制备的高性能厚膜电池势在必行.本文通过在D18:Y6二元活性层中加入少量富勒烯受体PC61BM,使得电池对厚度的敏感性显著降低. PC61BM的加入使厚膜活性层的电子和空穴迁移率明显提高,载流子传输更加平衡,并且显著降低了陷阱辅助复合.D18:Y6:PC61BM(1:1.6:0.2)三元电池在活性层厚度超过300 nm时,还能保持16%以上的效率,是目前性能最优异的厚膜有机太阳电池之一.

5H-dithieno[3,2-b:20,30-d]pyran-5-one unit yields efficient wide-bandgap polymer donors

Recently,great progress has been made in organic solar cells due to the emergence of high-performance nonfullerene acceptors[1-6].Over 16%and 17%power conversion efficiencies(PCEs)were achieved for nonfullerene-acceptor-based single-junction and tandem cells,respectively[7,8].Owing to complementary light absorption,wide-bandgap donor-acceptor(D-A)copolymers are ideal electron-donating partners for nonfullerene acceptors.However,efficient D-A copolymer donors are still limited.

Interface engineering gifts CsPbI2.25Br0.75 solar cells high performance

Organic-inorganic halide perovskite (ABX3) solar cells (PSCs)have made great progress in recent years [1]. The power conversion efficiency (PCE) has increased up to 25.2%(NREL Best Research-Cell Efficiency Chart, https://www.nrel.gov/pv/cell-efficiency.html, Accessed August 2019). However, they suffer from poor thermal stability due to the volatile A-site organic cations.

应用于高分子给体的稠环双内酯构筑单元

近年来,由于新型、高效高分子给体和非富勒烯受体的不断涌现,有机太阳电池性能得以快速提高.本文开发了基于稠环双内酯构筑单元的高分子给体材料,设计合成了两种五元稠环双内酯单元BL1和BL2,并进一步用这两种单元构筑了D-A共轭高分子给体P1和P2.BL1和BL2的分子结构通过X射线单晶衍射方法得到解析.BL1呈现完全平面化的分子结构,BL2则由于分子中两个相邻羰基的排斥作用而呈现一种扭曲平面结构.由于双内酯基团的强吸电子性以及BL1和BL2单元较大的稠环平面,高分子给体P1和P2展现出较深的HOMO能级和较好的空穴迁移率.基于上述高分子给体和非富勒烯受体IT-4F的太阳电池P1:IT-4F和P2:IT-4F实现了较高的开路电压,分别为0.96和0.94 V,能量转换效率分别为10.44%和7.31%.

钙钛矿叠层太阳电池

自2009年报道以来,钙钛矿太阳电池的能量转换效率从3.8%增长到25.5%,是发展最为迅猛的一类太阳电池.为了进一步提高能量转换效率,突破肖克利·奎伊瑟效率极限(S-Q极限),可以采用带隙互补的吸光材料制备多结太阳电池,从而提高太阳光利用率.由于钙钛矿吸光材料具有可溶液加工、带隙可调的特性,它是制备叠层太阳电池的理想材料.本文介绍了近年来基于钙钛矿材料的高效叠层太阳电池:钙钛矿/硅,钙钛矿/铜铟镓硒,钙钛矿/钙钛矿和钙钛矿/有机叠层太阳电池.作者首先介绍了叠层电池的结构和工作原理,之后分别总结了以上四种叠层电池的重要进展,最后围绕器件结构、效率、大面积制备、稳定性、成本以及铅毒性这六个方面,讨论了未来钙钛矿叠层太阳电池面临的挑战.目前钙钛矿/硅、钙钛矿/铜铟镓硒和钙钛矿/钙钛矿叠层电池的能量转换效率分别达到了29.1%、25.9%和25.6%,均超过了相应单结电池的最高效率,有巨大发展空间.钙钛矿叠层太阳电池将会吸引越来越多的关注,成为太阳能研究领域的重要方向.