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1.
Adv Mater ; : e1906995, 2020 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-32017283

RESUMO

The operational instability of perovskite solar cells (PSCs) is known to mainly originate from the migration of ionic species (or charged defects) under a potential gradient. Compositional engineering of the "A" site cation of the ABX3 perovskite structure has been shown to be an effective route to improve the stability of PSCs. Here, the effect of size-mismatch-induced lattice distortions on the ion migration energetics and operational stability of PSCs is investigated. It is observed that the size mismatch of the mixed "A" site composition films and devices leads to a steric effect to impede the migration pathways of ions to increase the activation energy of ion migration, which is demonstrated through multiple theoretical and experimental evidence. Consequently, the mixed composition devices exhibit significantly improved thermal stability under continuous heating at 85 °C and operational stability under continuous 1 sun illumination, with an extrapolated lifetime of 2011 h, compared to the 222 h of the reference device.

2.
Adv Mater ; 32(1): e1905674, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31737948

RESUMO

Although metal halide perovskite (MHP) light-emitting diodes (LEDs) have demonstrated great potential in terms of electroluminescence efficiency, the operational stability of MHP LEDs currently remains the biggest bottleneck toward their practical usage. Well-confined excitons/charge carriers in a dielectric/quantum well based on conventional spatial or potential confinement approaches substantially enhance radiative recombination in MHPs, but an increased surface-to-volume ratio and multiphase interfaces likely result in a high degree of surface or interface defect states, which brings about a critical environmentally/operationally vulnerable point on LED stability. Here, an effective solution is suggested to mitigate such drawbacks using strategically designed surface-2D/bulk-3D heterophased MHP nanograins for long-term-stable LEDs. The 2D surface-functionalized MHP renders significantly reduced trap density, environmental stability, and an ion-migration-immune surface in addition to a fast radiative recombination owing to its spatially and potentially confined charge carriers, simultaneously. As a result, heterophased MHP LEDs show substantial improvement in operational lifetime (T50 : >200 h) compared to conventional pure 3D or quasi-2D counterparts (T50 : < 0.2 h) as well as electroluminescence efficiency (surface-2D/bulk-3D: ≈7.70 ph per el% and pure 3D: ≈0.46 ph per el%).

3.
Nucleic Acids Res ; 48(D1): D882-D889, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31713622

RESUMO

The Encyclopedia of DNA Elements (ENCODE) is an ongoing collaborative research project aimed at identifying all the functional elements in the human and mouse genomes. Data generated by the ENCODE consortium are freely accessible at the ENCODE portal (https://www.encodeproject.org/), which is developed and maintained by the ENCODE Data Coordinating Center (DCC). Since the initial portal release in 2013, the ENCODE DCC has updated the portal to make ENCODE data more findable, accessible, interoperable and reusable. Here, we report on recent updates, including new ENCODE data and assays, ENCODE uniform data processing pipelines, new visualization tools, a dataset cart feature, unrestricted public access to ENCODE data on the cloud (Amazon Web Services open data registry, https://registry.opendata.aws/encode-project/) and more comprehensive tutorials and documentation.

4.
Medicine (Baltimore) ; 98(50): e18351, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31852136

RESUMO

Tenofovir disoproxil fumarate (TDF) is thought to cause varying degrees of hypophosphatemia in patients with chronic hepatitis B (CHB). Therefore, we investigated factors that cause hypophosphatemia in patients treated with TDF and methods to increase serum phosphorus concentrations in clinical practice.We completed a retrospective review of patients with CHB treated with TDF initially at Kosin University Gospel Hospital, Busan, Korea from January 2012 to January 2017. Subclinical hypophosphatemia and hypophosphatemia were defined as serum phosphorus below 3.0 mg/dL and 2.5 mg/dL, respectively.We screened 206 patients with CHB treated with TDF, among which 135 were excluded for the following reasons: baseline malignancy (59), limited data (50), co-administered other antivirals (14), hypophosphatemia at baseline (7), and other reasons (5). The final study population comprised 71 patients. Subclinical hypophosphatemia developed in 43 (60.5%) patients. Hypophosphatemia occurred in 18 patients (25.3%). Liver cirrhosis was the most significant predictor of hypophosphatemia (P = .038, OR = 3.440, CI = 1.082-10.937) Patients diagnosed with subclinical hypophosphatemia were encouraged to increase their intake of nuts and dairy products (25 patients) or reduce their alcohol intake (2), dose reduction of TDF (4) or placed under observation (4). Among patients with subclinical hypophosphatemia, serum phosphorus concentrations were elevated (>3.0 mg/dL) in 23 of 36 patients (63.8%). Increased nut and dairy intake increased phosphorus concentrations to more than 3.0 mg/dl in 16 of 25 patients (64.0%).Entecavir or tenofovir alafenamide fumarate (TAF) should be considered rather than TDF in patients with liver cirrhosis because of the risk of hypophosphatemia. Instead of stopping TDF treatment, encouraging increased intake of phosphorus-rich foods could increase serum phosphorus concentrations in clinical practice.


Assuntos
Antivirais/efeitos adversos , Hepatite B Crônica/tratamento farmacológico , Hipofosfatemia/induzido quimicamente , Tenofovir/efeitos adversos , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , República da Coreia , Estudos Retrospectivos , Fatores de Risco , Resultado do Tratamento
5.
Curr Protoc Bioinformatics ; 68(1): e89, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31751002

RESUMO

The Encyclopedia of DNA Elements (ENCODE) web portal hosts genomic data generated by the ENCODE Consortium, Genomics of Gene Regulation, The NIH Roadmap Epigenomics Consortium, and the modENCODE and modERN projects. The goal of the ENCODE project is to build a comprehensive map of the functional elements of the human and mouse genomes. Currently, the portal database stores over 500 TB of raw and processed data from over 15,000 experiments spanning assays that measure gene expression, DNA accessibility, DNA and RNA binding, DNA methylation, and 3D chromatin structure across numerous cell lines, tissue types, and differentiation states with selected genetic and molecular perturbations. The ENCODE portal provides unrestricted access to the aforementioned data and relevant metadata as a service to the scientific community. The metadata model captures the details of the experiments, raw and processed data files, and processing pipelines in human and machine-readable form and enables the user to search for specific data either using a web browser or programmatically via REST API. Furthermore, ENCODE data can be freely visualized or downloaded for additional analyses. © 2019 The Authors. Basic Protocol: Query the portal Support Protocol 1: Batch downloading Support Protocol 2: Using the cart to download files Support Protocol 3: Visualize data Alternate Protocol: Query building and programmatic access.

6.
Medicine (Baltimore) ; 98(38): e17260, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31568000

RESUMO

INTRODUCTION: This study is a prospective, assessor-blinded, parallel-group, randomized controlled pilot trial to explore the effectiveness of 12-week adjuvant moxibustion therapy for arthralgia in menopausal females at stage I to III breast cancer on aromatase inhibitor (AI) administration, compared with those receiving usual care. METHODS/DESIGN: Forty-six menopausal female patients with breast cancer who completed cancer therapy will be randomly allocated to either adjuvant moxibustion or usual care groups with a 1:1 allocation ratio. The intervention group will undergo 24 sessions of adjuvant moxibustion therapy with usual care for 12 weeks, whereas the control group will receive only usual care during the same period. The usual care consists of acetaminophen administration on demand and self-directed exercise education to manage AI-related joint pain. The primary outcome is the mean change of the worst pain level according to the Brief Pain Inventory-Short Form between the initial visit and the endpoint. The mean changes in depression, fatigue, and quality of life will also be compared between groups. Safety and pharmacoeconomic evaluations will also be included. DISCUSSION: Continuous variables will be compared by an independent t test or Wilcoxon rank-sum test between the adjuvant moxibustion and usual care groups. Adverse events will be analyzed using the chi-square or Fisher exact test. The statistical analysis will be performed by a 2-tailed test at a significance level of .05.


Assuntos
Inibidores da Aromatase/efeitos adversos , Artralgia/terapia , Neoplasias da Mama/tratamento farmacológico , Moxibustão , Idoso , Inibidores da Aromatase/uso terapêutico , Artralgia/induzido quimicamente , Artralgia/economia , Protocolos Clínicos , Análise Custo-Benefício , Feminino , Custos de Cuidados de Saúde , Humanos , Pessoa de Meia-Idade , Moxibustão/efeitos adversos , Moxibustão/economia , Projetos Piloto , Pós-Menopausa , Resultado do Tratamento
7.
J Am Chem Soc ; 141(42): 16553-16558, 2019 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-31529952

RESUMO

High efficiency perovskite solar cells have underpinned the rapid growth of the field. However, their low device stability limits further advancement. Hygroscopic lithium bis(trifluoromethanesulfonyl)imide (Li+TFSI-) and metal electrode are the main causes of the device instability. In this work, the redox reaction between lithium-ion endohedral fullerenes and 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobi-fluorene (spiro-MeOTAD) was controlled to optimize the amount of oxidized spiro-MeOTAD and antioxidizing neutral endohedral fullerenes. Application of this mixture to metal-free carbon nanotube (CNT)-laminated perovskite solar cells resulted in 17.2% efficiency with a stability time of more than 1100 h under severe conditions (temperature = 60 °C, humidity = 70%). Such high performance is attributed to the uninhibited charge flow, no metal-ion migration, and the enhanced antioxidizing activity of the devices.

8.
Sensors (Basel) ; 19(17)2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31480616

RESUMO

The main objectives of this study are to investigate the interference of multiple bottom reflected waves in the surface wave transmission (SWT) measurements in a plate and to propose a practical guide to source-and-receiver locations to obtain reliable and consistent SWT measurements in a plate. For these purposes, a series of numerical simulations, such as finite element modelling (FEM), are performed to investigate the variation of transmission coefficient of surface waves across a surface-breaking crack in various source-to-receiver configurations in plates. Main variables in this study include the crack depths (0, 10, 20, 30, 40 and 50 mm), plate thicknesses (150, 200, 300, 400 and 800 mm), source-to-crack distances (100, 150, 200, 250 and 300 mm) and receiver-to-crack distances. The validity of numerical simulation results was verified by comparison with results from experiments using Plexiglas specimens using two types of noncontact sensors (laser vibrometer and air-coupled sensor) in the laboratory. Based on simulation and experimental results in this study, practical guidelines for sensor-to-receiver locations are proposed to reduce the effects of the interference of bottom reflected waves on the SWT measurements across a surface-breaking crack in a plate. The findings in this study will help obtain reliable and consistent SWT measurements across a surface-breaking crack in plate-like structures.

9.
J Am Chem Soc ; 141(35): 13948-13953, 2019 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-31403287

RESUMO

Surface effects usually become negligible on the micrometer or sub-micrometer scale due to lower surface-to-bulk ratio compared to nanomaterials. In lead halide perovskites, however, their "soft" nature renders them highly responsive to the external field, allowing for extended depth scale affected by the surface. Herein, by taking advantage of this unique feature of perovskites we demonstrate a methodology for property manipulation of perovskite thin films based on secondary grain growth, where tuning of the surface induces the internal property evolution of the entire perovskite film. While in conventional microelectronic techniques secondary grain growth generally involves harsh conditions such as high temperature and straining, it is easily triggered in a perovskite thin film by a simple surface post-treatment, producing enlarged grain sizes of up to 4 µm. The resulting photovoltaic devices exhibit significantly enhanced power conversion efficiency and operational stability over a course of 1000 h and an ambient shelf stability of over 4000 h while maintaining over 90% of its original efficiency.

10.
Adv Mater ; 31(37): e1900111, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31343086

RESUMO

Halide perovskite colloidal quantum dots (CQDs) have recently emerged as a promising candidate for CQD photovoltaics due to their superior optoelectronic properties to conventional chalcogenides CQDs. However, the low charge separation efficiency due to quantum confinement still remains a critical obstacle toward higher-performance perovskite CQD photovoltaics. Available strategies employed in the conventional CQD devices to enhance the carrier separation, such as the design of type-Ⅱ core-shell structure and versatile surface modification to tune the electronic properties, are still not applicable to the perovskite CQD system owing to the difficulty in modulating surface ligands and structural integrity. Herein, a facile strategy that takes advantage of conjugated small molecules that provide an additional driving force for effective charge separation in perovskite CQD solar cells is developed. The resulting perovskite CQD solar cell shows a power conversion efficiency approaching 13% with an open-circuit voltage of 1.10 V, short-circuit current density of 15.4 mA cm-2 , and fill factor of 74.8%, demonstrating the strong potential of this strategy toward achieving high-performance perovskite CQD solar cells.

11.
J Ethnopharmacol ; 241: 112015, 2019 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-31173875

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: Atopic dermatitis (AD) is a pruritic, chronic, relapsing inflammatory skin disease. Gardenia jasminoides extract (GJE) has been used as a traditional remedy for the treatment of various inflammatory diseases, including AD. The specific effects of the extract components, which include crocin, geniposidic acid, and gardenoside, on inflammatory responses in AD are not entirely clear. AIM OF THE STUDY: We determined the effects of G. jasminoides extract with crocin removed (GJE-C) on AD-like skin lesions in Dermatophagoies farina crude extract (Dfe)-treated NC/Nga mice, a well-known AD mouse model. MATERIALS AND METHODS: To prepare the mice, 150 µl of 4% sodium dodecyl sulfate (SDS) was applied to the shaved dorsal skin or ear of NC/Nga mice 1 h before application of 100 mg Dfe. After 7 d, GJE-C was applied every day for 14 d. We performed behavior, histological, ELISA, assays to evaluate chemokines, cytokines, and skin barrier proteins in skin or serum samples from treated and untreated NC/Nga mice. RESULTS: Topical application of GJE-C improved the severity scores of the AD-like skin lesions, frequency of scratching, and ear swelling in Dfe-treated NC/Nga mice similar to the complete GJE. In addition, GJE-C also reduced serum IgE and chemokine levels as well as the inflammatory response. Topical application of GJE-C also resulted in decreased infiltration of inflammatory cells, such as mast cells, via reduction of Th2 inflammatory mediators, including interleukin (IL)-4, IL-5, and IL-13, pro-inflammatory cytokines, and chemokines, and increased skin barrier protein expression in Dfe-treated NC/Nga mice. The GJE components geniposidic acid and gardenoside inhibited the production of atopic-related chemokines in HaCaT cells, but inclusion of crocin dampened this inhibition of chemokine production. CONCLUSIONS: Together, these findings indicate that GJE-C may improve AD-like lesions by inhibiting the Th2 inflammatory response and expression of chemokines while increasing the expression of skin barrier proteins. These data provide experimental evidence that GJE-C may harbor therapeutic potential for AD.


Assuntos
Anti-Inflamatórios/uso terapêutico , Antígenos de Dermatophagoides/efeitos adversos , Citocinas/imunologia , Dermatite Atópica/tratamento farmacológico , Gardenia , Extratos Vegetais/uso terapêutico , Animais , Anti-Inflamatórios/farmacologia , Carotenoides/farmacologia , Carotenoides/uso terapêutico , Linhagem Celular , Sobrevivência Celular , Dermatite Atópica/imunologia , Dermatophagoides farinae , Humanos , Imunoglobulina E/sangue , Masculino , Camundongos , Extratos Vegetais/farmacologia , Pele/efeitos dos fármacos , Pele/imunologia , Pele/patologia , Células Th2/efeitos dos fármacos , Células Th2/imunologia
12.
Medicine (Baltimore) ; 98(15): e15174, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30985703

RESUMO

INTRODUCTION: This is a prospective, open-label, parallel-group, randomized controlled trial that evaluates the effectiveness and safety of adjuvant application of Jaungo (JUG) for radiation-induced dermatitis (RD) in breast cancer patients undergoing radiation therapy, in comparison with general supportive care (GSC). METHODS/DESIGN: Eighty female patients, who have been diagnosed with unilateral breast cancer, will be allocated to either the JUG or GSC group with an allocation ratio of 1:1 after breast conservation surgery, in the Kyung Hee University Korean Medicine Hospital, Seoul, Republic of Korea. Both the groups will be subjected to GSC, but only the JUG group participants will apply adjuvant JUG ointment on the irradiated skin for 6 weeks, twice a day. The primary outcome of this study is the assessment of incidence rate of RD using the Radiation Therapy Oncology Group (RTOG) for toxicity gradation of 2 or more. Maximum pain level, quality of life, adverse reactions, and pharmacoeconomic evaluations will also be included. DISCUSSION: The primary outcome will be statistically compared using the logrank test after estimating the survival curve using the Kaplan-Meier method. Continuous variables will be tested using independent t test or Mann-Whitney U test. The adverse events will be evaluated with Chi-square or Fisher exact test. All the data will be analyzed at a significance level of 0.05 (two-sided) with R software (The R Foundation). TRIAL REGISTRATION: CRIS (Clinical Research Information Service), KCT0003506, 14 February 2019.


Assuntos
Fármacos Dermatológicos/uso terapêutico , Medicamentos de Ervas Chinesas/uso terapêutico , Protetores contra Radiação/uso terapêutico , Radiodermatite/tratamento farmacológico , Dor Abdominal , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/radioterapia , Neoplasias da Mama/cirurgia , Protocolos Clínicos , Fármacos Dermatológicos/efeitos adversos , Fármacos Dermatológicos/economia , Medicamentos de Ervas Chinesas/efeitos adversos , Medicamentos de Ervas Chinesas/economia , Feminino , Humanos , Pessoa de Meia-Idade , Pomadas/efeitos adversos , Pomadas/economia , Pomadas/uso terapêutico , Seleção de Pacientes , Fitoterapia/efeitos adversos , Fitoterapia/economia , Protetores contra Radiação/efeitos adversos , Protetores contra Radiação/economia , Radioterapia/efeitos adversos , Adulto Jovem
13.
Nat Commun ; 10(1): 520, 2019 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-30705276

RESUMO

Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability.

14.
Adv Mater ; 31(47): e1803515, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30761623

RESUMO

Metal halide perovskites have been in the limelight in recent years due to their enormous potential for use in optoelectronic devices, owing to their unique combination of properties, such as high absorption coefficient, long charge-carrier diffusion lengths, and high defect tolerance. Perovskite-based solar cells and light-emitting diodes (LEDs) have achieved remarkable breakthroughs in a comparatively short amount of time. As of writing, a certified power conversion efficiency of 22.7% and an external quantum efficiency of over 10% have been achieved for perovskite solar cells and LEDs, respectively. Interfaces and defects have a critical influence on the properties and operational stability of metal halide perovskite optoelectronic devices. Therefore, interface and defect engineering are crucial to control the behavior of the charge carriers and to grow high quality, defect-free perovskite crystals. Herein, a comprehensive review of various strategies that attempt to modify the interfacial characteristics, control the crystal growth, and understand the defect physics in metal halide perovskites, for both solar cell and LED applications, is presented. Lastly, based on the latest advances and breakthroughs, perspectives and possible directions forward in a bid to transcend what has already been achieved in this vast field of metal halide perovskite optoelectronic devices are discussed.

15.
Nano Lett ; 19(4): 2223-2230, 2019 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-30517789

RESUMO

Single-walled carbon nanotubes (CNTs) has been considered as a promising material for a top electrode of perovskite solar cells owing to its hydrophobic nature, earth-abundance, and mechanical robustness. However, its poor conductivity, a shallow work function, and nonreflective nature have limited further enhancement in power conversion efficiency (PCE) of top CNT electrode-based perovskite solar cells. Here, we introduced a simple and scalable method to address these issues by utilizing an ex-situ vapor-assisted doping method. Trifluoromethanesulfonic acid (TFMS) vapor doping of the free-standing CNT sheet enabled tuning of conductivity and work function of the CNT electrode without damaging underneath layers. The sheet resistance of the CNT sheet was decreased by 21.3% with an increase in work function from 4.75 to 4.96 eV upon doping of TFMS. In addition, recently developed 2D perovskite-protected Cs-containing formamidium lead iodide (FACsPbI3) technology was employed to maximize the absorption. Because of the lowered resistance, better energy alignment, and improved absorption, the CNT electrode-based PSCs produced a PCE of 17.6% with a JSC of 24.21 mA/cm2, VOC of 1.005 V, and FF of 0.72. Furthermore, the resulting TFMS-doped CNT-PSCs demonstrated higher thermal and operational stability than bare CNT and metal electrode-based devices.

16.
Sensors (Basel) ; 20(1)2019 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-31905886

RESUMO

The main objectives of this study are to develop a non-destructive test method for evaluating delamination defects in concrete by the Impact-echo test using multi-channel elastic wave data and to verify the validity of the proposed method by experimental studies in the laboratory. First, prototype equipment using an eight-channel linear sensor array was developed to perform elastic wave measurements on the surface of the concrete. In this study, three concrete slab specimens (1500 mm (width) by 1500 mm (length) by 300 mm (thickness)), with simulated delamination defects of various lateral dimensions and depth, were designed and constructed in the laboratory. Multi-channel elastic wave signals measured on the three concrete specimens were converted to the frequency-phase velocity image by using the phase-shift method. A data processing method was proposed to extract the dominant propagating waves and non-propagating waves from the dispersion images. The dominant wave modes were used to evaluate delamination defects in concrete. It was demonstrated that the surface wave velocity values were useful for characterizing the shallow delamination defects in concrete. In addition, the peak frequency of non-propagating wave modes extracted from the dispersion images gives information on the lateral dimensions and depths of the delamination defects. This study also discussed the feasibility of combined use of the results from propagating and non-propagating wave modes to better understand the information on delamination defects in concrete. As will be discussed, the multi-channel elastic wave measurements enable more accurate, consistent, and rapid measurements and data processing for evaluation of delamination defects in concrete than the single-channel sensing method.

17.
J Am Chem Soc ; 140(49): 17255-17262, 2018 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-30449094

RESUMO

The precise control of stoichiometric balance and ionic defects on the surface of solution-processed perovskite is critical to the performance and stability of perovskite solar cells (pero-SCs). Here, we introduce a low-cost and stable conjugated donor polymer (PTQ10) as interfacial layer in the planar n-i-p structured pero-SCs. The polymer was applied to the perovskite intermediate phase before the thermal annealing. This treatment significantly reduced the loss of surface organic cation during thermal annealing. Importantly, the kinetics of phase conversion of perovskite was influenced, and perovskite crystal showed a more preferential orientation. Moreover, the polymer proved to be an effective hole extraction layer due to the proper energy alignment with perovskite. Finally, a champion power conversion efficiency of the planar pero-SCs was achieved at 21.2% with a high fill factor of 81.6%. The devices also showed great ambient and thermal stability. This work presents a facile way of perovskite surface control to achieve high-performance pero-SCs.

18.
Adv Mater ; 30(44): e1804402, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30277609

RESUMO

A cryogenic process is introduced to control the crystallization of perovskite layers, eliminating the need for the use of environmentally harmful antisolvents. This process enables decoupling of the nucleation and the crystallization phases by inhibiting chemical reactions in as-cast precursor films rapidly cooled down by immersion in liquid nitrogen. The cooling is followed by blow-drying with nitrogen gas, which induces uniform precipitation of precursors due to the supersaturation of precursors in the residual solvents at very low temperature, while at the same time enhancing the evaporation of the residual solvents and preventing the ordered precursors/perovskite from redissolving into the residual solvents. Using the proposed techniques, the crystallization process can be initiated after the formation of a uniform precursor seed layer. The process is generally applicable to improve the performance of solar cells using perovskite films with different compositions, as demonstrated on three different types of mixed halide perovskites. A champion power conversion efficiency (PCE) of 21.4% with open-circuit voltage (VOC ) = 1.14 V, short-circuit current density ( JSC ) = 23.5 mA cm-2 , and fill factor (FF) = 0.80 is achieved using the proposed cryogenic process.

19.
ACS Appl Mater Interfaces ; 10(46): 39590-39598, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30259726

RESUMO

Fullerenes have attracted considerable interest as an electron-transporting layer in perovskite solar cells. Fullerene-based perovskite solar cells produce no hysteresis and do not require high-temperature annealing. However, high power conversion efficiency has been only achieved when the fullerene layer is thermally evaporated, which is an expensive process. In this work, the limitations of a solution-processed fullerene layer have been identified as high crystallinity and the presence of remnant solvents, in contrast to a thermally deposited C60 film, which has low crystallinity and no remaining solvents. As a solution to these problems, a mixed C60 and C70 solution-processed film, which exhibits low crystallinity, is proposed as an electron-transporting layer. The mixed-fullerene-based devices produce power conversion efficiencies as high as that of the thermally evaporated C60-based device (16.7%) owing to improved fill factor and open-circuit voltage. In addition, by vacuum-drying the mixed fullerene film, the power conversion efficiency of the solution-processed perovskite solar cells is further improved to 18.0%. This improvement originates from the enhanced transmittance and charge transport by removing the solvent effect. This simple and low-cost method can be easily used in any type of solar cells with fullerene as the electron-transporting layer.

20.
Nat Commun ; 9(1): 3021, 2018 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-30069012

RESUMO

Compositional engineering has been used to overcome difficulties in fabricating high-quality phase-pure formamidinium perovskite films together with its ambient instability. However, this comes alongside an undesirable increase in bandgap that sacrifices the device photocurrent. Here we report the fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability. Incorporation of 1.67 mol% of 2D phenylethylammonium lead iodide into the precursor solution enables the formation of phase-pure formamidinium perovskite with an order of magnitude enhanced photoluminescence lifetime. The 2D perovskite spontaneously forms at grain boundaries to protect the formamidinium perovskite from moisture and suppress ion migration. A stabilized power conversion efficiency (PCE) of 20.64% (certified stabilized PCE of 19.77%) is achieved with a short-circuit current density exceeding 24 mA cm-2 and an open-circuit voltage of 1.130 V, corresponding to a loss-in-potential of 0.35 V, and significantly enhanced operational stability.

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