Fast Organic Cation Exchange in Colloidal Perovskite Quantum Dots toward Functional Optoelectronic Applications.

Colloidal quantum dots with lower surface ligand density are desired for preparing the active layer for photovoltaic, lighting, and other potential optoelectronic applications. In emerging perovskite quantum dots (PQDs), the diffusion of cations is thought to have a high energy barrier, relative to that of halide anions. Herein, we investigate the fast cross cation exchange approach in colloidal lead triiodide PQDs containing methylammonium (MA+) and formamidinium (FA+) organic cations, which exhibits a significantly lower exchange barrier than inorganic cesium (Cs+)-FA+ and Cs+-MA+ systems. First-principles calculations further suggest that the fast internal cation diffusion arises due to a lowering in structural distortions and the consequent decline in attractive cation-cation and cation-anion interactions in the presence of organic cation vacancies in mixed MA+-FA+ PQDs. Combining both experimental and theoretical evidence, we propose a vacancy-assisted exchange model to understand the impact of structural features and intermolecular interaction in PQDs with fewer surface ligands. Finally, for a realistic outcome, the as-prepared mixed-cation PQDs display better photostability and can be directly applied for one-step coated photovoltaic and photodetector devices, achieving a high photovoltaic efficiency of 15.05% using MA0.5FA0.5PbI3 PQDs and more precisely tunable detective spectral response from visible to near-infrared regions.

Controllable Colloidal Synthesis of MAPbI3 Perovskite Nanocrystals for Dual-Mode Optoelectronic Applications.

This study demonstrates an acetate ligand (AcO-)-assisted strategy for the controllable and tunable synthesis of colloidal methylammonium lead iodide (MAPbI3) perovskite nanocrystals (PNCs) for efficient photovoltaic and photodetector devices. The size of colloidal MAPbI3 PNCs can be tuned from 9 to 20 nm by changing the AcO-/MA ratio in the reaction precursor. In situ observations and detailed characterization results show that the incorporation of the AcO- ligand alters the formation of PbI6 octahedral cages, which controls PNC growth. A well-optimized AcO-/MA ratio affords MAPbI3 PNCs with a low defect density, a long carrier lifetime, and unique solid-state isotropic properties, which can be used to fabricate solution-processed dual-mode photovoltaic and photodetector devices with a conversion efficiency of 13.34% and a detectivity of 2 × 1011 Jones, respectively. This study provides an avenue to further the precisely controllable synthesis of hybrid PNCs for multifunctional optoelectronic applications.

Dual-Interface Modulation with Covalent Organic Framework Enables Efficient and Durable Perovskite Solar Cells.

Dual-interface modulation including buried interface as well as the top surface has recently been proven to be crucial for obtaining high photovoltaic performance in lead halide perovskite solar cells (PSCs). Herein, for the first time, the strategy of using functional covalent organic frameworks (COFs), namely HS-COFs for dual-interface modulation, is reported to further understand its intrinsic mechanisms in optimizing the bottom and top surfaces. Specifically, the buried HS-COFs layer can enhance the resistance against ultraviolet radiation, and more importantly, release the tensile strain, which is beneficial for enhancing device stability and improving the order of perovskite crystal growth. Furthermore, the detailed characterization results reveal that the HS-COFs on the top surface can effectively passivate the surface defects and suppress non-radiation recombination, as well as optimize the crystallization and growth of the perovskite film. Benefiting from the synergistic effects, the dual-interface modified devices deliver champion efficiencies of 24.26% and 21.30% for 0.0725 cm2 and 1 cm2 -sized devices, respectively. Moreover, they retain 88% and 84% of their initial efficiencies after aging for 2000 h under the ambient conditions (25 °C, relative humidity: 35-45%) and a nitrogen atmosphere with heating at 65 °C, respectively.

Hybrid Block Copolymer/Perovskite Heterointerfaces for Efficient Solar Cells.

Solution processable semiconductors like organics and emerging lead halide perovskites (LHPs) are ideal candidates for photovoltaics combining high performance and flexibility with reduced manufacturing cost. Moreover, the study of hybrid semiconductors would lead to advanced structures and deep understanding that will propel this field even further. Herein, a novel device architecture involving block copolymer/perovskite hybrid bulk heterointerfaces is investigated, such a modification could enhance light absorption, create an energy level cascade, and provides a thin hydrophobic layer, thus enabling enhanced carrier generation, promoting energy transfer and preventing moisture invasion, respectively. The resulting hybrid block copolymer/perovskite solar cell exhibits a champion efficiency of 24.07% for 0.0725 cm2 -sized devices and 21.44% for 1 cm2 -sized devices, respectively, together with enhanced stability, which is among the highest reports of organic/perovskite hybrid devices. More importantly, this approach has been effectively extended to other LHPs with different chemical compositions like MAPbI3 and CsPbI3 , which may shed light on the design of highly efficient block copolymer/perovskite hybrid materials and architectures that would overcome current limitations for realistic application exploration.

Ligand-Assisted Coupling Manipulation for Efficient and Stable FAPbI3 Colloidal Quantum Dot Solar Cells.

For emerging perovskite quantum dots (QDs), understanding the surface features and their impact on the materials and devices is becoming increasingly urgent. In this family, hybrid FAPbI3 QDs (FA: formamidium) exhibit higher ambient stability, near-infrared absorption and sufficient carrier lifetime. However, hybrid QDs suffer from difficulty in modulating surface ligand, which is essential for constructing conductive QD arrays for photovoltaics. Herein, assisted by an ionic liquid formamidine thiocyanate, we report a facile surface reconfiguration methodology to modulate surface and manipulate electronic coupling of FAPbI3 QDs, which is exploited to enhance charge transport for fabricating high-quality QD arrays and photovoltaic devices. Finally, a record-high efficiency approaching 15 % is achieved for FAPbI3 QD solar cells, and they retain over 80 % of the initial efficiency after aging in ambient environment (20-30 % humidity, 25 °C) for over 600 h.

Logistic regression models of cytokines in differentiating vitreoretinal lymphoma from uveitis.

BACKGROUND: Vitreoretinal lymphoma (VRL) can commonly masquerade as chronic idiopathic uveitis due to its nonspecific clinical presentation. Thus, its early diagnosis is difficult. In this study, new logistic regression models were used to classify VRL and uveitis. Additionally, the diagnostic performance of interleukin (IL)-10, the IL-10/IL-6, and the Interleukin Score for IntraOcular Lymphoma Diagnosis (ISOLD) are evaluated. METHODS: Sixty-nine aqueous humors (AH) (46 VRL, 23 uveitis) and 65 vitreous humors (VH) (49 VRL, 16 uveitis) were collected from a single-center retrospective cohort. Logistic regression models were conducted based on IL-6 and IL-10. The cut-off values, area under the receiver operating characteristic curve (ROC) curve (AUC), sensitivity and specificity of IL-10, the IL-10/IL-6, the ISOLD, and the models were calculated from the ROC. Furthermore, Spearman's rank correlation analysis was performed to determine cytokine levels in VH and AH. RESULTS: We redefined the cut-off values of IL-10, the IL-10/IL-6, the ISOLD, and the logistic regression models. In AH, the AUC values of IL-10, ISOLD, IL10/IL6, and the model were 0.91, 0.953, 0.952, and 0.967. In VH, they were 0.93, 0.95, 0.954, and 0.954, respectively. IL-6 (r = 0.7844) and IL-10 (r = 0.8506) in AH and VH showed a strong correlation. CONCLUSIONS: IL-6 and IL-10 levels were introduced into new logistic regression models. The diagnostic efficacy of the models improved compared to the indicators mentioned above among Chinese patients. Additionally, the models could predict the probability of VRL more accurately. A strong correlation of cytokine levels showed the great potential of AH as prioritized auxiliary diagnostic for VRL.

Highly efficient A-site cation exchange in perovskite quantum dot for solar cells.

The mixed cation colloidal Cs1-XFAXPbI3 perovskite quantum dots (PQDs) obtained by cation exchange between CsPbI3 and FAPbI3 PQDs have been reported to exhibit enhanced photovoltaic performance. However, the cation exchange mechanism requires further in-depth investigation in terms of both material properties and device application. In this work, the impact of PQD weight ratio, PQD concentration, and host solvent polarity during cation exchange is comprehensively investigated for the first time. In addition, the whole exchange process under varying conditions is monitored by photoluminescence spectroscopy. As a result, we observe extremely fast cation exchange (∼20 min) under a condition at a CsPbI3/FAPbI3 PQD weight ratio of 1:1, a concentration of 70 mg/ml, and a host solvent using toluene. Moreover, we directly fabricate a PQD solar cell device using these obtained mixed cation Cs0.5FA0.5PbI3 PQDs and achieved an enhanced power conversion efficiency of 14.58%. We believe that these results would provide more insights into the cation exchange in emerging PQDs toward efficient photovoltaic fabrication and application.

Tailoring Phase Alignment and Interfaces via Polyelectrolyte Anchoring Enables Large-Area 2D Perovskite Solar Cells.

Ruddlesden-Popper phase 2D perovskite solar cells (PSCs) exhibit improved lifetime while still facing challenges such as phase alignment and up-scaling to module-level devices. Herein, polyelectrolytes are explored to tackle this issue. The contact between perovskite and hole-transport layer (HTL) is important for decreasing interfacial non-radiative recombination and scalable fabrication of uniform 2D perovskite films. Through exploring compatible butylamine cations, we first demonstrate poly(3-(4-carboxybutyl)thiophene-2,5-diyl)-butylamine (P3CT-BA) as an efficient HTL for 2D PSCs due to its great hydrophilicity, relatively high hole mobility and uniform surface. More importantly, the tailored P3CT-BA has an anchoring effect and acts as the buried passivator for 2D perovskites. Consequently, a best efficiency approaching 18 % was achieved and we further first report large-area (2×3 cm2 , 5×5 cm2 ) 2D perovskite minimodules with an impressive efficiency of 14.81 % and 11.13 %, respectively.

Homojunction Perovskite Quantum Dot Solar Cells with over 1 µm-Thick Photoactive Layer.

The solution-processed solar cells based on colloidal quantum dots (QDs) reported so far generally suffer from poor thickness tolerance and it is difficult for them to be compatible with large-scale solution printing technology. However, the recently emerged perovskite QDs, with unique high defect tolerance, are particularly well-suited for efficient photovoltaics. Herein, efficient CsPbI3 perovskite QD solar cells are demonstrated first with over 1 µm-thick active layer by developing an internal P/N homojunction. Specifically, an organic dopant 2,2'-(perfluoronaphthalene-2,6-diylidene) dimalononitrile (F6TCNNQ) is introduced into CsPbI3 QD arrays to prepare different carrier-type QD arrays. The detailed characterizations reveal successful charge-transfer doping of QDs and carrier-type transformation from n-type to p-type. Subsequently, the P/N homojunction perovskite QD solar cell is assembled using different carrier-type QDs, delivering an enhanced power conversion efficiency of 15.29%. Most importantly, this P/N homojunction strategy realizes remarkable thickness tolerance of QD solar cells, showing a record high efficiency of 12.28% for a 1.2 µm-thick QD active-layer and demonstrating great potential for the future printing manufacturing of QDs solar cells.

Aromatic amine-assisted pseudo-solution-phase ligand exchange in CsPbI3 perovskite quantum dot solar cells.

Here, a pseudo-solution-phase ligand exchange (p-SPLE) strategy is developed for fabricating a CsPbI3 quantum dot (QD) solar cell. Using short organic aromatic ligands to partly replace the long-chain ligands in a QD solution, the p-SPLE treated CsPbI3 QD solar cell had an enhanced power conversion efficiency of up to 14.65% together with improved stability.

Synthetic method, growth mechanism and electrochemical properties of PbSnS2 nanosheets for supercapacitors.

Facile hydrothermally synthesized PbSnS2 nanosheets with various morphologies were developed to obtain high performance electrode materials for supercapacitors. A precipitation-dissolution mechanism was proposed to demonstrate the growth process of PbSnS2. The as-prepared nanosheets exhibited superior capacitance (678.8 F g-1 at 50 mV s-1) and a long cycle life (95.5% capacitance retention after 100 000 cycles at 5 A g-1).

[Determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds by solid phase extraction-high performance liquid chromatography].

A new method was established for the determination of neohesperidin dihydrochalcone (NHDC) and naringin dihydrochalcone (Naringin DC) in feeds by solid phase extraction-high performance liquid chromatography (SPE-HPLC). The samples were extracted by methanol and were purified on an HLB solid-phase extraction column. Chromatographic separation was achieved on an XB-C18 column (150 mm×4.6 mm, 5 µm) by linear gradient elution using methanol/water as the mobile phase. The analytes were detected by the diode array detector (DAD). The results revealed a good linear correlation (r>0.999) between the peak areas and mass concentrations of dihydrochalcone sweeteners in the range of 0.2-49.0 mg/L. The limits of quantification (LOQs) of NHDC and Naringin DC were 0.02 and 0.01 mg/kg, respectively. Intra- and inter-day reproducibilities were 0.7%-4.1% and 0.9%-6.0%, respectively. The spiked recoveries for the samples and relative standard deviations (RSDs) were 86.2%-105.0% and 1.0%-6.3% (n=3), respectively. It is both sensitive and repeatable for the quantitative determination of neohesperidin dihydrochalcone and naringin dihydrochalcone in feeds, and thus, can be used to effectively reduce interference in feeds.

Design and Experimental Research of a Rotary Micro-Actuator Based on a Shearing Piezoelectric Stack.

The working principle of a rotating micro-actuator based on a piezoelectric stack was theoretically analyzed and experimentally verified. The actuator is compact in structure, and the key component is the shearing piezoelectric stack. The piezoelectric stack is used to drive the micro-rotor via an electromechanical transition, which produces high-speed rotation of the micro-rotor. We first established the dynamic model of the micro-actuator and numerically analyzed the motion of this model. The step displacement output was observed by simulation, and the step increment is quite large. For experimental verification, we fabricated the piezoelectric micro-actuator with a size of 12 mm × 10 mm × 8 mm and mass of 4.12 g and conducted a series of experiments. The results show qualitative agreement with the theoretical results; the maximum output speed of the micro-actuator is 5.86 × 10 5 µ rad/s, and the motion resolution is 0.64 µ rad, which is greater than that of most traditional piezoelectric actuators. The proposed micro-actuator offers superior performance in driving of selected small objects, such as in micro-/nano-processing and cell operation.

[Determination of 21 plant growth regulator residues in fruits by QuEChERS-high performance liquid chromatography-tandem mass spectrometry].

A method for the simultaneous detection of 21 plant growth regulators in fruits by QuEChERS-high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed. The samples were initially extracted with acetonitrile containing 1% (v/v) acetic acid, followed by clean-up using the powder of magnesium sulfate and C18. The resulting samples were separated on a C18 column, and detected under positive and negative multiple reactions monitoring (MRM) mode through polarity switching between time segments. The matrix-matched external standard calibration curves were used for quantitative analysis. The linearities of chlormequat chloride, mepiquat chloride, choline chloride, cyclanilide, forchlorfenuron, thidiazuron, inabenfide, paclobutrazol, uniconazole and triapenthenol were in the concentration range of 0.1-500 microg/L, daminozide and 6-benzylaminopurine in the concentration range of 1.0-500 microg/L, 2,3,5-triiodobenzoic acid, 2,4-D, cloprop, 4-chlorophenoxyacetic acid (4-CPA) and trinexapac-ethyl in the concentration range of 2.0-1 000 microg/L, abscisic acid (ABA), gibberellic acid (GA3), 1-naphthaleneacetic acid (NAA) and indol-3-ylacetic acid (IAA) in the concentration range of 10-1000 microg/L, with the correlation coefficients higher than 0.990. The limits of detection and the limits of quantification of the method were 0.020-6.0 microg/kg and 0.10-15.0 microg/kg, respectively. For all the samples, the average spiked recoveries ranged from 73.0% to 111.0%, and the relative standard deviations (RSDs, n = 6) were in the range of 3.0% - 17.2%. The method is quick, easy, effective, sensitive and accurate, and can meet the requirements for the determination of the 21 plant growth regulator residues in fruits.

[Short-term observation of Acrysof Toric intraocular lens for correction of preoperative astigmatism in patients having cataract surgery].

OBJECTIVE: To evaluate the results of Toric intraocular lens (IOL) for correction of preoperative astigmatism in patients having cataract phacoemulsification. METHODS: It was a prospective case series study. Seventy-one eyes (60 patients) had implantation of Acrysof Toric IOL. logMAR uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), preexisting corneal astigmatism, residual refractive sphere and cylinder, and toric IOL axis were measured. Four residual astigmatism models were compared according to their axis postoperatively: neutral, against-the-rule (ATR, 180 ± 15 degrees), with-the-rule (WTR, 90 ± 15 degrees) and oblique (OB, 45/135 ± 30 degrees). Rank sum test and Friedman test was used to analyze these data. RESULTS: Three months postoperatively, the median distant UCVA increased significantly from 0.80 to 0.20, residual refractive astigmatism decreased significantly from 2.02 D to 0.67 D. The mean Toric IOL axis rotation was 1.63 ± 1.83 degrees, with rotation less than 5.00 degrees in 96% of eyes. For uncorrected near visual acuity, group ATR fared the best results and the difference between group ATR and groups WTR, neutral and OB was statistically significant. For UCVA, there was no statistically significant difference between group ATR and groups neutral and OB. CONCLUSIONS: Acrysof Toric IOL implantation is a predictable, safe and effective method to correct preexisting corneal astigmatism in patients having cataract phacoemulsification. A pseudophakic eye after Acrysof Toric IOL implantation with low residual ATR myopic astigmatism is beneficial for obtaining a better uncorrected near and distant visual acuities.