Recent strategies to improve moisture stability in metal halide perovskites materials and devices

At present,the stability of the new generation of solar cells based on hybrid perovskites is the bottleneck for their practical applications.Photochemical effects,high temperature,ultraviolet light,humidity and other known or still unknown factors might cause reduction of effectiveness or even irreversible loss of materials properties due to decomposition of functional layers within perovskite solar cells(PSCs).These factors alone have a serious impact on each component of the device,while their combinations lead to much more complicated effects and consequences.This review focuses on the stability of PSCs and the degradation of the device in a humid environment.We assess the instability factors and deep-seated principles of evolution of the device structure in a humidity environment with the emphasis on the influence on their interrelations.The related solutions are reviewed from the perspective of the encapsulation,perovskite active layer,carrier transport layer and electrodes.Combined with the latest research,we believe that the waterproof strategy of PSCs requires either tight encapsulation or thorough modifications in the device itself.Therefore,it is important to develop feasible strategies to improve the overall device stability over humid according to the target characteristics of various devices.     

An enrichment device of silica-based monolithic material and its application to determine micro-carbaryl by NIRS

Silica-based monolithic column material was synthesized and an enrichment device was fabricated with the material by assembling the material inside a glass column.The enrichment device was applied for the determination of micro-carbaryl with near-infrared spectroscopy(NIRS).The aqueous solutions of carbaryl passed through the device and the carbaryl was enriched on the surface of the material where diffuse reflection NIR spectra were measured.These procedures of enrichment and measurement ensured to conc...     

Organic thin-film solar cells: Devices and materials

In recent years, the performance of organic thin-film solar cells has gained rapid progress, of which the power conversion efficiencies (ηp) of 3%-5% are commonly achieved, which were difficult to obtain years ago and are improving steadily now. The ηp of 7.4% was achieved in the year 2010, and ηp of 9.2% was disclosed and confirmed at website of Mitsubishi Chemical in April, 2011. The promising future is that the ηp of 10% is achievable according to simulation results. Apparently, these are attributed to material innovations, new device structures, and also the better understanding of device physics. This article summarizes recent progress in organic thin-film solar cells related to materials, device structures and working principles. In the device functioning part, after each brief summary of the working principle, the methods for improvements, such as absorption increment, organic/electrode interface engineering, morphological issues, are addressed and summarized accordingly. In addition, for the purpose of increasing exciton diffusion efficiency, the benefit from triplet exciton, which has been proposed in recent years, is highlighted. In the active material parts, the chemical nature of materials and its impact on device performance are discussed. Particularly, emphasis is given toward the insight for better understanding device physics as well as improvements in device performance either by development of new materials or by new device architecture.     

Ricinus communis agglutinin I functionalisation of poly(methyl methacrylate) (PMMA) as a substrate for microfluidic device

We report a functionalisation strategy which is able to generate Ricinus communis agglutinin I (RCA 120) modified PMMA microfluidic device for binding and culturing living cells. The functionalisation is achieved by standard amine-aldehyde (Schiff base) reaction through the cross-linker, glutaraldehyde. To prove the ability of the RCA 120 modified PMMA surface, the PC 12 cell line (rat pheochromocytoma cells) has been captured and cultured by the microfluidic device. In the presence of tunicamycin, the dose/time-dependence on decreasing of binding affinity of RCA 120 modified device with PC 12 cell is also observed. The experimental results demonstrate that the lectin-functionalized microfluidic device can be employed as efficient cell culturing platform, and has a great promise of being used as a powerful tool for monitoring the interaction of drug with living cell.     

Dual interfacial engineering for efficient Cs2AgBiBr6 based solar cells

The emerging lead-free halide double perovskite solar cells have attracted widespread attentions due to their long-term stability and non-toxicity, but suffer from the low device performance. One efficiencylimiting factor is the improper contacts between the halide double perovskite and anode/cathode electrodes. Here, we improve the efficiency and stability of the bismuth-halide double perovskite based solar cells by a synergistic interface design for both electron and hole transport layers(ETL/HTL). The results show that the modification of the TiO_2 ETL with a thin hydrophobic C60 layer and replacement of the lithium-doped small molecule HTL with an un-doped conjugated polymer lead to higher surface quality of perovskite film and better energy-level alignment at the contacts. As a result, the optimized device shows reduced trap density, suppressed charge recombination and enhanced charge extraction, leading to an increase of 69% in device efficiency. In addition, the device also exhibits superior stability in ambient environment, heat stress and light bias after interface optimization. This work provides an efficient strategy for the device optimization of the emerging lead-free perovskite solar cells.     

The effect of interfacial diffusion on device performance of polymer solar cells: a quantitative view by active-layer doping

The diffusion of constituent materials at interfaces is one of the key factors for device performance and stability.In this work,the effect of interfacial diffusion of a classic interfacial material PFN on device performance of polymer solar cells was studied quantitatively by doping PFN into active layer based on P3HT:PC61BM blend.The PCEs of devices with 550 ppm PFN decrease to half compared to those of the control devices without PFN,which are mainly attributed to the decrease of short-circuit current(Jsc)and fill factor(FF).Advanced analyses of equivalent circuit,absorption spectra,and atomic force microscopy indicates that the presence of PFN in the active layer increases the leakage current,decreases the aggregation of P3HT,and reduces the phase separation.This research reveals the physical mechanism of interfacial diffusion in device performance and provides a basis for further improving the performance and stability of PSCs.     

Recent progress of hybrid cathode interface layer for organic solar cells

Organic solar cells(OSCs) have gained conspicuous progress during the past few decades due to the development of materials and upgrading of the device structure. The power conversion efficiency(PCE) of the single-junction device had surpassed 19%. The cathode interface layer(CIL), by optimizing the connection between the active layer and the cathode electrode, has become a momentous part to strengthen the performances of the OSCs. Simultaneously, CIL is also indispensable to illustrating the wor...     

STUDY ON DIRECT HYDROLYSIS OF METHYL FORMATE TO FORMIC ACID

Both batch reactor and continuous tubular reactor were designed for the hydrolysis of methylformate to formic acid.By the former device,the effects of some reaction conditions,such as reactiontemperature,pressure,water/ester ratio and the addition of methanol and formic acid into the startingmaterial,on the induction period,the equilibrium time and the hydrolysis conversion of methyl formatewere investigated.By the latter device,as the length/diameter ratio of the reaction tube was large,itwas similar to an ideal plug flow reactor.The results obtained from the two reactors on the samereaction were compared.     

EXPERIMENT TECHNIQUE RESEARCH OF SINGLE CRYSTAL X-RAY DIFFRACTION UNDER HIGH PRESSURE

We have set up the high pressure device used for single crystal X-ray diffraction, determined the X-ray absorption curve of the device on Nicolet four-circle diffractometer, established the data collection programme of a fixed φ scheme, and corrected the offsets of the optical centering of the crystal by using a reflection which is measured in eight different orientations. The mixture ratio of methanol: ethanol: water 16: 3: 1 was used as a pressure medium, high pressure calibration was based on the wavelength shift of the R_1 fluorescence line of ruby, and the pressure of 100 kbar was obtained.     

Electroluminescence performances of 1,1-bis(4-(N,N-dimethylamino)phenyl)-2,3,4,5-tetraphenylsilole based polymers in three cathode architectures

A new silole monomer with two 4-(N,N-dimethylamino)phenyl substitutions on silicon atom as designed and synthesized.Three copolymers PF-N-HPS1,PF-N-HPS10 and PF-N-HPS20 were then obtained by copolymerizations of 2,7-fluorene derivatives with the silole monomer at feed ratios of 1%,10%,and 20%.Their UV-vis absorption,electrochemical,photoluminescent,and electroluminescent (EL) properties were investigated.PF-N-HPS possessed HOMO levels of 5.25-5.58 eV,and showed green emissions.Using PF-N-HPS as the emissive layer,three different polymer light-emitting diodes were fabricated as device A with ITO/PEDOT/PF-N-HPS/Al,device B with ITO/PEDOT/PF-N-HPS/Ba/Al,and device C with ITO/PEDOT/PF-N-HPS/TPBI/Ba/Al.For the device A,PF-N-HPS only showed very low EL efficiency of 0.06-0.33 cd/A,indicating that the Al cathode could not inject electron efficiently to the emissive polymers containing the 4-(N,N-dimethylamino)phenyl groups.For the device B,low work function Ba supplied better electron injections,and the EL efficiency could be improved to 0.85-1.44 cd/A.TPBI with a deep HOMO level of 6.2 eV could enhance electron transport and hole blocking.Thus modified recombinations and largely elevated EL efficiency of 4.56-7.96 cd/A were achieved for the device C.The separation of the emissive layer and metal cathode with the TPBI layer may also suppress exciton quenching at the cathode interface.     

Redox active polymer metal chelates for use in flexible symmetrical supercapacitors: Cobalt-containing poly(acrylic acid) polymer electrolytes

The novel polymer metal chelate electrolytes(polychelates)were prepared by incorporation of cobalt sulfate(Co)into poly(acrylic acid)(PAA)host matrix.Quasi-solid state supercapacitor devices were fabricated using polychelates,PAA-Co X(X:3,5,7,and 10)where X represents the doping fraction(w/w)of Co in PAA.All polymer metal electrolytes were showed excellent bending-stretching properties,thermal stability and electrochemical durability with an optimum ionic conductivity of 3.15×10^-4 S cm^-1.Hierarchically porous activated carbon and nano-sized conductive carbon were used to form carbon composite symmetrical device electrodes.The electric double-layer capacitor(EDLC)and redox reactions of Co-incorporated polychelates at the interfaces of porous activated carbon provided an optimum specific capacitance of 341.33 F g^-1 with a device of PAA-Co7,which is at least 15 times enhancement compared to the device of pristine PAA.The PAA-Co7 device also provided energy density of 21.25 Wh kg^-1 at a power density of 117.69 W kg^-1.A prolonged cyclic stability of the device exhibited superior capacitive performance after 10,000 charge-discharge cycles and the maintained 90%of its initial performance.In addition,the supercapacitor with a dimension of 1.5 cm×3 cm containing PAA-Co7 successfully operated the red-blue-green(RGB)LED light.     

Enhanced efficiency and stability in Sn-based perovskite solar cells with secondary crystallization growth

The conversion efficiencies reported for Tin(Sn)halide-based perovskite solar cells(PSCs)fall a large gap behind those of lead halide-based PSCs,mainly because of poor film quality of the former.Here we report an efficient strategy based on a simple secondary crystallization growth(SCG)technique to improve film quality for tin halide-based PSCs by applying a series of functional amine chlorides on the perovskite surface.They were discovered to enhance the film crystallinity and suppress the oxidation of Sn²⁺remarkably,hence reduce trap state density and non-irradiative recombination in the absorber films.Furthermore,the SCG film holds the band levels matching better with carrier transport layers and herein favoring charge extraction at the device interfaces.Consequently,a champion device efficiency of 8.07% was achieved alo ng with significant enhancements in VOC and JSC,in contrast to 5.35% of the control device value.Moreover,the SCG film-based devices also exhibit superior stability comparing with the control one.This work explicitly paves a novel and general strategy for developing high performance lead-free PSCs.     

On-chip classification of micro-particles using laser light scattering and machine learning

The rapid detection of microparticles exhibits a broad range of applications in the field of science and technology. The proposed method differentiates and identifies the 2 μm and 5 μm sized particles using a laser light scattering. The detection method is based on measuring forward light scattering from the particles and then classifying the acquired data using support vector machines. The device is composed of a microfluidic chip linked with photosensors and a laser device using optical fiber....     

Printable and stable all-polymer solar cells based on non-conjugated polymer acceptors with excellent mechanical robustness

All-polymer solar cells(all-PSCs)trigger enormous commercial applications,and great progress has been made in recent years.However,from small-area devices to large-area modules,the poor adaption of the materials for printing methods and the large efficiency loss are still great challenges.Herein,three novel non-conjugated polymer acceptors(PTH-Y,PTClm-Yand PTClo-Y)are developed for all-PSCs.It can be found that non-conjugated polymer acceptors can effectively minimize the technique and efficiency gaps between small-area spin-coating and large-area blade-printing method,which can facilitate the preparation of large-area flexible device.By directly inheriting the spin-coating condition,the blade-coating processed device based on PTCloY achieves an impressive power conversion efficiency(PCE)of 12.42%,comparable to the spin-coating processed one(12.74%).Such a non-conjugated polymer system also can well tolerate large-scale preparation and flexible substrate.Notable PCE of 11.94%for large-area rigid device and 11.56%for large-area flexible device are obtained,which is the highest value for large-area flexible all-PSCs fabricated by blade-coating.In addition,the non-conjugated PTClo-Y-based devices show excellent thermal stability and mechanical robustness.These results demonstrate that the non-conjugated polymer acceptors are potential candidates for the fabrication of highly-efficient,large-area and robust flexible all-PSCs by printing methods.     

Hexa-Coordinate phosphorus Chemistry and Life Chemistry

The amino acids' side chains were acting as the relay device to regulate the chemical reactivi-ties of the N-phosphoryl amino acids. These modulation effects were performed through the partici-pation of the phosphoryl group.     

Post-treatment by an ionic tetrabutylammonium hexafluorophosphate for improved efficiency and stability of perovskite solar cells

Interface engineering is an effective way to improve efficiency and long-term stability of perovskite solar cells(PSCs).Herein,an ionic compound tetrabutylammonium hexafluorophosphate(TP6)is adopted to passivate surface defects of the perovskite film.It is found that TP6 effectively reduced the surface defects,especially at the grain boundaries where the defects are abundant.Meanwhile,the exposed long alkyl chains and fluorine atoms in the TP6 enhanced the moisture stability of the perovskite film due to its strong hydrophobicity.In addition,the driving force of charge carrier separation and transport is increased by enlarged built-in potential.Consequently,the power conversion efficiency(PCE)of PSCs is significantly improved from 20.59% to 22.41%by increased open-circuit voltage(V_oc)and fill factor(FF).The unencapsulated device with TP6 treatment exhibits better stability than the control device,and the PCE retains-80%of its initial PCE after 30 days under 15%-25%relative humidity in storage,while the PCE of the control device declines by more than 50%.     

CARRIER PHOTOGENERATION IN POLY（N-VINYL-CARBAZOLE）-BASED PHOTOCONDUCTIVE THIN-FILM DEVICES

In this paper, photoexcitation processes in the bilayer devices based on inorganic materials and poly（N-vinylcarbazole） （PVK） were investigated. In order to clarify the roles of inorganic materials in photoconductive properties of bilayer devices, TiO2 and ZnS were chosen to combine with PVK. A model for generation of photocurrent （Iph） in single layer device of PVK was obtained. It is deduced that the recombination rate constant （Pcomb） and the ionization rate constant （y） ofexcitons should be considered as the most important factors for Iph. For inorganic materials （TiO2 or ZnS）/PVK bilayer devices, in reverse bias of-4 V, the photocurrent of 115 mA/cm^2 in the TiO2/PVK device was observed, but the photocurrent in the ZnS/PVK device was only 10 mA/cma under the illumination light of 340 nm and the light intensity of 14.2 mW/cm^2. The weaker photocurrent is attributed to the absorption of ZnS within UV region and the energy offset at the interface between PVK and ZnS, which impedes the transport of charge carriers.     

INFLUENCE OF TRACES OF WATER ON THE SYNTHESIS AND ELECTROLUMINESCENCE PROPERTIES OF POLY(2-METHOXY, 5- (2'''' -ETHYLHEXYL OXY)- 1, 4-PHENYLENE VINYLENE)

It was found that traces of water in the reaction medium would result in a great increase of gel and a decrease ofmolecular weight of the poly(2-methoxy, 5-(2'-ethylhexyloxy)-1, 4-phenylene vinylene) during the polymerization, whichultimately led to inferior film qualities and device properties. The device (ITO/PEDOT/MEH-PPV/Ba/Al) with MEH-PPVprepared under dry conditions has an external quantum efficiency of above 2.0%.     

Machine learning enables intelligent screening of interface materials towards minimizing voltage losses for p-i-n type perovskite solar cells

Interface engineering is proved to be the most important strategy to push the device performance of the perovskite solar cell(PSC) to its limit, and numerous works have been conducted to screen efficient materials. Here, on the basis of the previous studies, we employ machine learning to map the relationship between the interface material and the device performance, leading to intelligently screening interface materials towards minimizing voltage losses in p-i-n type PSCs. To enhance the explain...     

Recent progress in functionalized electrophosphorescent iridium(Ⅲ) complexes

Iridium(Ⅲ) complexes are one of the most important electrophosphorescent dyes with tunable emissions in the range of visible and near infrared lights,high photoluminescence yields and short lifetimes for high-efficiency organic light-emitting diodes(OLED) with 100% exciton harvesting.This review summarizes the recent development of electroluminescent Ir~(3+) complexes functionalized with host-featured carrier-transporting groups,with emphasis on correlations between functionalization,optoelectronic properties and device performance.According to the introducing approaches,the complexes were sorted with conjugated and aliphatic linkages,as well as the types of functional groups.The modification effect on physical properties and the state-of-the-art device performances were discussed.