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Benefiting from the superior optoelectronic properties and low-cost manufacturing techniques, mixed-halide wide bandgap (WBG) perovskite solar cells (PSCs) are currently considered as ideal top cells for fabricating multi-junction or tandem solar cells, which are designed to beyond the Shockley-Queisser (S-Q) limit of single-junction solar cells. However, the poor long-term operational stability of WBG PSCs limits their further employment and hinders the marketization of multi-junction or tandem solar cells. In this review, recent progresses on improving environmental stability of mixed-halide WBG PSCs through different strategies, including compositional engineering, additive engineering, interface engineering, and other strategies, are summarized. Then, the outlook and potential direction are discussed and explored to promote the further development of WBG PSCs and their applications in multi-junction or tandem solar cells.

Solvent residue is inevitable to occur in solution processed thin films, but its influence on the thin film quality has not been identified and addressed to date. Methylammonium acetate (MAAc) ionic liquid has recently been realized as an environmentally friendly solvent for solution processed perovskites. The specific high viscosity, low vapor pressure and strong association with perovskite precursor of the MAAc solvent is a double-edged sword, which endowed an advantageously ambient air operational and anti-solvent free perovskite deposition, but the MAAc is likely to be retained within the film and bring in detrimental effects on device performance of the corresponding solar cells. Herein, we reported a novel route to eliminate the residual solvent via a facial hydrochloric acid (HCl) annealing post-treatment (HAAP). In particular, chemical displacement reaction between the incorporated HCl and residual MAAc can be initiated to form volatile MACl and HAc, efficiently extracting MAAc residue. In the meanwhile, the stimulated mass transport via downward penetration and upward escape can trigger secondary perovskite growth with enlarged grain size and smoothened surface, leading to reduced defect state and improved interfacial contact intimacy, and also partial chloride ions are able to enter the crystal lattice to stabilize perovskite phase structure. As a result, a champion efficiency up to 20.78% originating from enhanced Voc was achieved, and more than 96% of its initial efficiency can be maintained after 1000 h shelf-storage.

The elucidation of intermolecular interactions for the systematic control of nucleation and crystallization is key to produce perovskite photovoltaics with superior performance. In this study, we a...

Low-dimensional Ruddlesden–Popper (LDRP) perovskites have attracted great attention due to their superior stabilities. However, these LDRP perovskites are required to grow vertically with respect to the substrates to enable efficient charge transport for highly efficient and stable perovskite solar cells (PSCs). Herein, we introduce a strategy to form a highly vertically oriented LDRP phase by introducing bromide (Br) into organic ammonium spacer of butylamine (BA) lead halide perovskites, i.e., (C4H9NH3)2MA4Pb5BrxI16−x. The LDRP perovskites with a small amount of Br (I–Br–I system with Br : PbI2 = 2 : 5 (molar ratio)) show the best abilities to form high-quality thin films and excellent vertical crystalline orientation, which facilitates charge transport and thus leads to highly efficient PSCs. As a result, a high champion PCE of 15.75% is achieved for the I–Br–I LDRP PSC compared to that of the pure iodine (I–I–I) device (12.15%). This work provides a new way to achieve efficient and stable LDRP PSCs.

Two-dimensional Ruddlesden–Popper layered metal-halide perovskites have attracted increasing attention for their desirable optoelectronic properties and improved stability compared to their three-dimensional counterparts. However, such perovskites typically consist of multiple quantum wells with a random well width distribution. Here, we report phase-pure quantum wells with a single well width by introducing molten salt spacer n-butylamine acetate, instead of the traditional halide spacer n-butylamine iodide. Due to the strong ionic coordination between n-butylamine acetate and the perovskite framework, a gel of a uniformly distributed intermediate phase can be formed. This allows phase-pure quantum well films with microscale vertically aligned grains to crystallize from their respective intermediate phases. The resultant solar cells achieve a power conversion efficiency of 16.25% and a high open voltage of 1.31 V. After keeping them in 65 ± 10% humidity for 4,680 h, under operation at 85 °C for 558 h, or continuous light illumination for 1,100 h, the cells show

All-inorganic lead halide perovskites are promising candidates for optoelectronic applications. However, fundamental questions remain over the component interaction in the perovskite precursor solution due to the limitation of the most commonly used solvents of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). Here, we report an interaction tailoring strategy for all-inorganic CsPbI3-x Brx perovskites by involving the ionic liquid solvent methylammonium acetate (MAAc). C=O shows strong interaction with lead (Pb2+ ) and N-H⋅⋅⋅I hydrogen bond formation is observed. The interactions stabilize the perovskite precursor solution and allow production of the high-quality perovskite films by retarding the crystallization. Without the necessity for antisolvent treatment, the one-step air-processing approach delivers photovoltaic cells regardless of humidity, with a high efficiency of 17.10 % along with long operation stability over 1500 h under continuous light illumination.

Valinomycin, a cyclic peptide, was incorporated into a biomimetic lipid membrane tethered to the surface of a gold (111) electrode. Electrochemical impedance spectroscopy was used to study the ionophore properties of the peptide, and polarization modulation infrared reflection absorption spectroscopy was employed to determine the conformation and orientation of valinomycin in the membrane. The combination of these two techniques provided unique information about the ionophore mechanism where valinomycin transports ions across the membrane by creating a complex with potassium ions and forming an ion pair with a counter anion. The ion pair resides within the hydrophobic fragment of the membrane and adopts a small angle of ∼22° with respect to the surface normal. This novel study provides new insights explaining the valinomycin ion transport mechanism in model biological membranes.

To gain a better knowledge of structural variations (SVs) in Xiang pig, we used next-generation sequencing to analyze the Xiang pigs with larger (XL) or smaller litter sizes (XS). Our analysis yielded 28,040 putative SVs in the Xiang pig. These SVs distributed throughout all of chromosomes. Some functional regions including exons and untranslated regions were less varied than introns and intergenic regions. We detected 4637 and 4119 specific SVs, which contained 1697 and 1582 genes in XL and XS group, respectively. These genes were mainly enriched in the well-known pathways involved in development and reproduction processes. Population validation was carried out on 50 SVs candidates using PCR method in 144 Xiang pig crowds. All of 50 SVs were confirmed by PCR method and 14 SVs were associated with the litter size of Xiang pigs. These results may be helpful for the elucidation of growth and reproduction regulation in Xiang pig.

In this paper, the electrochemiluminescence (ECL) behavior of a hole-transport polymer, poly [9,9-bis(3'-(N,N-dimethylamino) propyl)-2,7-fluorene]-alt-2,7-(9,9-dio ctylfluorene)] (PFN) was examined with the purpose of finding a novel organic ECL emitter. It was found that the PFN exhibits self-electrochemiluminescence (self-ECL) without any exogenous co-reactants. Quite different from the traditional ECL, the addition of tripropyl amine (TPA) quenched the self-ECL of PFN. PFN ECL intensity reaches a peak during electrochemical oxidation process due to the superposition of self-enhanced ECL, and aggregation quenching of excited state by PFN excimer formation. Aluminum tris(8-quinolinolate) (AlQ3) doped with PFN recovers luminescence intensity with restraining quenching effect via ECL resonance energy transfer from PFN to AlQ3, giving rise to a stable luminescence signal, and hence sensory detection of nitroaromatics. The limits of detections for nitroaromatics can reach down to a level of 10−22 M. This work sets the stage for a novel organic polymer-based ECL emitter without using any toxic exogenous co-reactant, and presents a practical avenue for a prototype of realising sensory detection through signal stabilization via energy resonance energy transfer (ERET).

The lower charge mobility of organic semiconductors relative to that of inorganic semiconductors is a thorny problem that still has not been resolved. Here, a new type of arrangement of grid-shaped organic semiconductors with extremely low values of internal reorganization energies (IREs) for both hole (0.056 eV) and electron (0.078 eV) transfer processes has been designed and investigated by density functional theory (DFT) calculations. The structural, thermodynamic and electronic properties of grid spirofluorene (GSF) consisting of four spirobifluorenes have been discussed thoroughly. Our analyses of these unique grid structures indicate that they possess a stringent structure and very weak ring strain energy, and may be easily synthesized in the laboratory. Interestingly, GSF1, GSF2, and GSF9 possess both small hole and lower electron transfer reorganization energies (

Rapid progress of digital communications in the Big Data and Internet of things has stimulated the exploration of next-generation data storage devices. Among various candidates, resistive switching (RS) memory devices and artificial synapses are in the spotlight due to their low power consumption, downscaling potential, and fast operation speed. The exceptional electronic and mechanical characteristics of metal halide perovskites (MHPs) have greatly promoted their application in nonvolatile high density, low-cost, and flexible memory devices. Here, we distill the current state-of-the-art and highlight recent advances of MHP based RS memory devices and artificial synapses. The general structure and characteristics of RS memory devices are first introduced. Afterwards we discuss the excellent memory behaviors accompanied by detailed working mechanisms. Finally, the current challenges and future development prospects are also discussed. This review article is expected to pave the way in the rational design of MHP based memory devices and artificial synapses with unprecedented performance improvement.

Recently, the power conversion efficiency (PCE) of perovskite solar cells (PSC) based on organic-inorganic hybrid Pb halide perovskites has reached 25.2 %. However, the toxicity of Pb has still been a main concern for the large-scale commercialization of Pb-based PSCs. Efforts have been made during the past few years to seek eco-friendly Pb-free perovskites, and it is a growing consensus that Sn is the best choice as Pb alternative over any other Pb-free metal elements. Among Sn-based perovskites, all-inorganic cells are promising candidates for PSCs owing to their more suitable bandgap, better stability, and higher charge mobility compared to the organic-inorganic hybrid counterparts. However, the poor phase stability of all-inorganic Sn-based perovskites (AISPs) and low PCE of their PSCs are most challenging in the field at present. Herein, recent developments on PSCs based on AISPs, including CsSnX3 and Cs2 SnX6 (X=Br, I), are comprehensively reviewed. Primarily, the intrinsic characteristics of the two AISPs are overviewed, including crystallographic property, band structure, charge carrier property, and defect property. Sequentially, state-of-the-art progress, regarding the photovoltaic application of AISPs as light absorber, is summarized. At last, current challenges and future opportunities of AISP-based PSCs are also discussed.

Low-dimensional Ruddlesden-Popper (LDRP) perovskite solar cells (PSCs) have attracted increasing attention due to their excellent long-term stability over three-dimensional (3D) counterparts. However, the introduction of insulated long-range bulkier organic ammonium spacers hindered the charge transport. Here, the short-range organic ammonium spacers, 1-amino-3-butene hydrochloride (BEACl) and 3-butyn-1-amine hydrochloride (BYACl), were employed to construct LDRP perovskites, instead of common butylamine hydrochloride (BACl). We found that charge transport can be significantly improved by controlling the tunneling effect. Moreover, highly oriented and flat perovskite films without pinholes were obtained. Consequently, high PCEs, exceeding 16% for BEA- and 15% for BYA-based devices, which is much higher than that of the BA-based analogous device (13.8%), were achieved. Most importantly, the BEA- and BYA-based LDRP perovskite films and devices show much improved stability. The finding is of great significance for the exploration of new organic ammonium spacers for highly efficient and stable LDRP PSCs.

The Guizhou pony (GZP) is an indigenous species of equid found in the mountains of the Guizhou province in southwest China. We selected four regions of the equine leukocyte antigen (ELA), includingDQA,DRA,DQB,andDRB,and used them to assess the diversity of the major histocompatibility complex (MHC) class II gene using direct sequencing technology.DRAhad the lowestdN/dSratio (0.560) compared with the other three loci, indicating thatDRAwas conserved and could be conserved after undergoing selective processes. NineDQA, fiveDQB, nineDRA,and sevenDRBcodons were under significant positive selection at the antigen binding sites (ABS), suggesting that the selected residues in ABS may play a significant role in the innate immune system of the GZP. Two GZP alleles were shared with Przewalski’s horse, and six older GZP haplotypes had a better relationship with other horse species by one or two mutational steps, indicating that the GZP may be a natural ancient variety of equid. The specific diversity of ABS and the numbers of unique haplotypes in the evolutionary process affords this species a better genetic fitness and ability to adapt to the native environment.

Hole transport materials are crucial for efficient charge extraction in perovskite solar cells to achieve high power conversion efficiency and stability. Herein, the hole transport properties of the 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenylamine)9,9′-spirobifluorene (spiro-OMeTAD) thin films with a dopant lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) are investigated through impedance spectroscopy. Upon doping, we observe a dispersive hole transport with nearly a 100-fold increase in the hole mobility compared with the pristine spiro-OMeTAD films. The hole mobilities slightly decrease with increasing electric fields for both films, exhibiting a negative electric field dependence of mobility due to the positional disorder. Subsequently, the charge carrier density of the LiTFSI-doped spiro-OMeTAD film is three orders of magnitude higher than that of the pristine film. The LiTFSI dopant induces two different electrical regions in the doped thin film, which can be reflected through impedance spectroscopy. The presented investigation through impedance spectroscopy is of high practical interest for the development of hole transport materials and the optimization of the transport layer doping in perovskite solar cells.

The phase control and ordered crystal growth play a crucial role in the efficiency and stability of all-inorganic perovskite solar cells (PSCs). However, the innate dynamics of crystal growth driving the stable phase and high performance are unknown. Here, we for the first time unraveled that the degree of lattice strain is responsible for the suppression of the δ phase growth by in situ Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS) technique. We shadow the internal crystal structural changes in real time and successfully decoupled crystal growth dynamics under different substrate temperatures. The symmetrical crystal lattice and vertical substrate growth were finally achieved. This finding provides insights on the inorganic perovskite crystal growth and has significant benefit for high performing all-inorganic PSCs.

Compared to planar carbazole, the molecular conjugation of iminodibenzyl (Id) was destroyed by a C–C bond and a twisted structure was formed, which exhibited blue-shifted ultralong phosphorescence with a lifetime of 402 ms in a crystal under ambient conditions. For the presence of an oscillating C–C bond between the two benzene rings in Id, more than one molecular configuration in the crystal was discovered by X-ray single-crystal analysis. Moreover, its ultralong phosphorescence color changed from blue to green by varying the excitation wavelength in solution at 77 K. Theoretical calculations also confirmed that different molecular configurations had certain impact on the phosphorescent photophysical properties. This result will allow a major step forward in expanding the scope of ultralong organic phosphorescent (UOP) materials, building a bridge to realize the relationship between molecular structure and UOP property.

Solution-processable small molecules (SMs) have attracted intense attention due to their definite molecular structures, less batch-to-batch variation, and easier structure control. Herein, two new SM donors based on substituted isatin unit (DI3T, DI3T-2F) are synthesized and applied as electron donors with the mixture of PC71 BM to construct organic photovoltaics. As a result, 5,6-difluoro isatin derivative (DI3T-2F) obtains a power conversion efficiency of 7.80% by a simple solution spin-coating fabrication process without any additives, solvent, or thermal annealing process. More intuitively, due to stronger intermolecular interaction and higher hole mobility after the incorporation of fluorine atoms in end units, the devices present good tolerance to active layer thickness. The results indicate that DI3T-2F shows promising potential for large-scale printing processes and flexible application of efficient small molecule organic solar cells.