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1.
Chem Commun (Camb) ; 55(74): 11059-11062, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31453991

RESUMO

The addition of a polar-hydrophobic methylammonium trifluoroacetate ionic liquid tailors the hydrophobicity of halide-perovskite precursor solutions and assists in grain growth. This unique additive also functionalizes the grain boundaries via polar-polar interactions, thereby enhancing the optoelectronic properties and chemical stability of perovskites. This study opens the door to the solution hydrophobicity control towards high-performance perovskite devices.

2.
ChemSusChem ; 12(15): 3431-3447, 2019 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-31025513

RESUMO

Photopowered energy systems (PPESs), which simultaneously achieve power conversion and energy storage, are one of the most promising auxiliaries to fulfill the giant and diversified power demand in modern society. Devices with a low cost, wearable, compact structure and the potential to add a variety of features (such as photochromic, flexible, textile, and wearable) have received extensive research attention. Photo-supercapacitors are becoming one of the most extensively researched PPESs due to their ease of fabrication, mitigation of solar irradiation discontinuities, and the promotion of renewable energy utilization, and these devices have been fabricated with different combinations of photovoltage devices and energy-storage technologies. This review summarizes the development of photo-supercapacitors that integrate third-generation solar cells and supercapacitors, with a focus on materials alignment, performance, structure design, and application. Finally, current challenges, possible solutions, and future perspectives are discussed.

3.
Angew Chem Int Ed Engl ; 58(17): 5587-5591, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30779292

RESUMO

An easy and scalable methylamine (MA) gas healing method was realized for inorganic cesium-based perovskite (CsPbX3 ) layers by incorporating a certain amount of MAX (X=I or Br) initiators into the raw film. It was found that the excess MAX accelerated the absorption of the MA gas into the CsPbX3 film and quickly turned it into a liquid intermediate phase. Through the healing process, a highly uniform and highly crystalline CsPbX3 film with enhanced photovoltaic performance was obtained. Moreover, the chemical interactions between a series of halides and MA gas molecules were studied, and the results could offer guidance in further optimizations of the healing strategy.

4.
Adv Mater ; 30(22): e1707143, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29682798

RESUMO

Effective passivation and stabilization of both the inside and interface of a perovskite layer are crucial for perovskite solar cells (PSCs), in terms of efficiency, reproducibility, and stability. Here, the first formamidinium lead iodide (δ-FAPbI3 ) polymorph passivated and stabilized MAPbI3 PSCs are reported. This novel MAPbI3 /δ-FAPbI3 structure is realized via treating a mixed organic cation MA x FA1-x PbI3 perovskite film with methylamine (MA) gas. In addition to the morphology healing, MA gas can also induce the formation of δ-FAPbI3 phase within the perovskite film. The in situ formed 1D δ-FAPbI3 polymorph behaves like an organic scaffold that can passivate the trap state, tunnel contact, and restrict organic-cation diffusion. As a result, the device efficiency is easily boosted to 21%. Furthermore, the stability of the MAPbI3 /δ-FAPbI3 film is also obviously improved. This δ-FAPbI3 phase passivation strategy opens up a new direction of perovskite structure modification for further improving stability without sacrificing efficiency.

5.
Angew Chem Int Ed Engl ; 56(26): 7674-7678, 2017 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-28524450

RESUMO

Methylammonium-mediated phase-evolution behavior of FA1-x MAx PbI3 mixed-organic-cation perovskite (MOCP) is studied. It is found that by simply enriching the MOCP precursor solutions with excess methylammonium cations, the MOCPs form via a dynamic composition-tuning process that is key to obtaining MOCP thin films with superior properties. This simple chemical approach addresses several key challenges, such as control over phase purity, uniformity, grain size, composition, etc., associated with the solution-growth of MOCP thin films with targeted compositions.

6.
ACS Appl Mater Interfaces ; 8(45): 31413-31418, 2016 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-27797470

RESUMO

Recently, perovskite solar cells with high photovoltaic performance based on methylammonium lead halide have attracted great interest due to the superior physical properties of the perovskite optical absorption layer. Here, we investigate the interface carrier transport properties of CH3NH3PbI3 film by applying the reported treatment with methylamine gas, to reveal the possible mechanism of high performance perovskite-sensitized solar cell results. It is found that the crystal structure and surface morphology are effectively improved by the room-temperature repair of methylamine atmosphere. The preferred 110 orientation results in a slightly larger band gap, which may contribute to the better energy level matching and carrier transport. Further investigations on relaxation time and electron mobility confirm the significantly enhanced carrier diffusion length, revealing the important role of optimized crystallization on charge transport properties, which may be helpful to seek high-powered perovskite solar cells by optimizing the perovskite synthetic process.

7.
Angew Chem Int Ed Engl ; 55(47): 14723-14727, 2016 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-27766739

RESUMO

Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH4 PbI3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH3 NH3 PbI3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH4 PbI3 -to-CH3 NH3 PbI3 transformation process. The chemical origins of this transformation are studied at various length scales.

8.
Chem Commun (Camb) ; 52(45): 7273-5, 2016 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-27181497

RESUMO

The α→δ phase transition, which occurs favorably in planar films of a black α-HC(NH2)2PbI3 (α-FAPbI3) perovskite in the amibent, is retarded when α-FAPbI3 is deposited upon mesoporous TiO2 scaffolds. It is hypothesized that this is due to the synergistic effect of the partial encapsulation of α-FAPbI3 by the mesoporous TiO2 and the elevated activation energy for the transition reaction associated with the substantial increase of the TiO2/α-FAPbI3 interfacial area in the mesoscopic system.

9.
J Am Chem Soc ; 138(17): 5535-8, 2016 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-27088448

RESUMO

Here we demonstrate a radically different chemical route for the creation of HC(NH2)2PbI3 (FAPbI3) perovskite thin films. This approach entails a simple exposure of as-synthesized CH3NH3PbI3 (MAPbI3) perovskite thin films to HC(═NH)NH2 (formamidine or FA) gas at 150 °C, which leads to rapid displacement of the MA(+) cations by FA(+) cations in the perovskite structure. The resultant FAPbI3 perovskite thin films preserve the microstructural morphology of the original MAPbI3 thin films exceptionally well. Importantly, the myriad processing innovations that have led to the creation of high-quality MAPbI3 perovskite thin films are directly adaptable to FAPbI3 through this simple, rapid chemical-conversion route. Accordingly, we show that efficiencies of perovskite solar cells fabricated with FAPbI3 thin films created using this route can reach ∼18%.

10.
Chem Commun (Camb) ; 52(19): 3828-31, 2016 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-26867948

RESUMO

High-quality formamidinium lead iodide (FAPbI3) perovskite thin films are fabricated via organic cation exchange. With ammonia lead iodide (NH4PbI3) as the starting material, the NH4(+) in NH4PbI3 could be gradually substituted by FA(+) in formamidine acetate (FA-Ac) and simultaneously transformed to the pure phase α-FAPbI3 at elevated temperature.

11.
J Am Chem Soc ; 138(3): 750-3, 2016 Jan 27.
Artigo em Inglês | MEDLINE | ID: mdl-26730744

RESUMO

We demonstrate the feasibility of a nonsalt-based precursor pair--inorganic HPbI3 solid and organic CH3NH2 gas--for the deposition of uniform CH3NH3PbI3 perovskite thin films. The strong room-temperature solid-gas interaction between HPbI3 and CH3NH2 induces transformative evolution of ultrasmooth, full-coverage perovskite thin films at a rapid rate (in seconds) from nominally processed rough, partial-coverage HPbI3 thin films. The chemical origin of this behavior is elucidated via in situ experiments. Perovskite solar cells, fabricated using MAPbI3 thin films thus deposited, deliver power conversion efficiencies up to 18.2%, attesting to the high quality of the perovskite thin films deposited using this transformative process.

12.
Carbohydr Polym ; 137: 732-738, 2016 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-26686186

RESUMO

A bio-based hybrid film containing chitosan (CS) and silver nanowires (AgNWs) has been prepared by a simple casting technique. X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-visible spectroscopy were employed to characterize the structure of bio-based film. The bio-based hybrid film showed unique performance compared with bare chitosan film. The incorporated nano-silver could improve the strength properly. The results revealed that AgNWs in CS film, improved its tensile strength more than 62% and Young modulus 55% compared with pure chitosan film. On the other hand tensile strength was increased 36.7% with AgNPs. Importantly, the film also exhibited conductivity and antibacterial properties, which may expand its future application.


Assuntos
Anti-Infecciosos/química , Quitosana/química , Nanofios/química , Prata/química , Escherichia coli/efeitos dos fármacos , Microscopia Eletrônica de Varredura , Espectroscopia de Infravermelho com Transformada de Fourier , Estresse Mecânico , Difração de Raios X
13.
Nanoscale ; 8(12): 6265-70, 2016 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-26549434

RESUMO

The microstructure of the solid-PbI2 precursor thin film plays an important role in the intercalation crystallization of the formamidinium lead triiodide perovskite (α-HC(NH2)2PbI3). It is shown that microstructurally engineered PbI2 thin films with porosity and low crystallinity are the most favorable for conversion into uniform-coverage, phase-pure α-HC(NH2)2PbI3 perovskite thin films. Planar perovskite solar cells fabricated using these thin films deliver power conversion efficiency (PCE) up to 13.8%.

14.
J Phys Chem Lett ; 6(23): 4827-39, 2015 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-26560696

RESUMO

The use of organometal trihalide perovskites (OTPs) in perovskite solar cells (PSCs) is revolutionizing the field of photovoltaics, which is being led by advances in solution processing of OTP thin films. First, we look at fundamental phenomena pertaining to nucleation/growth, coarsening, and microstructural evolution involved in the solution-processing of OTP thin films for PSCs from a materials-science perspective. Established scientific principles that govern some of these phenomena are invoked in the context of specific literature examples of solution-processed OTP thin films. Second, the nature and the unique characteristics of OTP thin-film microstructures themselves are discussed from a materials-science perspective. Finally, we discuss the challenges and opportunities in the characterization of OTP thin films for not only gaining a deep understanding of defects and microstructures but also elucidating classical and nonclassical phenomena pertaining to nucleation/growth, coarsening, and microstructural evolution in these films. The overall goal is to have deterministic control over the solution-processing of tailored OTP thin films with desired morphologies and microstructures.

15.
J Phys Chem Lett ; 6(12): 2292-7, 2015 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-26266607

RESUMO

The crystal morphology of organolead trihalide perovskite (OTP) light absorbers can have profound influence on the perovskite solar cells (PSCs) performance. Here we have used a combination of conventional transmission electron microscopy (TEM) and high-resolution TEM (HRTEM), in cross-section and plan-view, to characterize the morphologies of a solution-processed OTP (CH3NH3PbI3 or MAPbI3) within mesoporous TiO2 scaffolds and within capping and planar layers. Studies of TEM specimens prepared with and without the use of focused ion beam (FIB) show that FIBing is a viable method for preparing TEM specimens. HRTEM studies, in conjunction with quantitative X-ray diffraction, show that MAPbI3 perovskite within mesoporous TiO2 scaffold has equiaxed grains of size 10-20 nm and relatively low crystallinity. In contrast, the grain size of MAPbI3 perovskite in the capping and the planar layers can be larger than 100 nm in our PSCs, and the grains can be elongated and textured, with relatively high crystallinity. The observed differences in the performance of planar and mesoscopic-planar hybrid PSCs can be attributed in part to the striking differences in their perovskite-grain morphologies.


Assuntos
Compostos de Cálcio/química , Compostos Organometálicos/química , Óxidos/química , Energia Solar , Titânio/química , Metilaminas/química , Microscopia Eletrônica de Transmissão , Tamanho da Partícula , Porosidade , Difração de Raios X
16.
Angew Chem Int Ed Engl ; 54(33): 9705-9, 2015 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-26118666

RESUMO

We report herein the discovery of methylamine (CH3NH2) induced defect-healing (MIDH) of CH3NH3PbI3 perovskite thin films based on their ultrafast (seconds), reversible chemical reaction with CH3NH2 gas at room temperature. The key to this healing behavior is the formation and spreading of an intermediate CH3NH3PbI3⋅xCH3NH2 liquid phase during this unusual perovskite-gas interaction. We demonstrate the versatility and scalability of the MIDH process, and show dramatic enhancement in the performance of perovskite solar cells (PSCs) with MIDH. This study represents a new direction in the formation of defect-free films of hybrid perovskites.


Assuntos
Compostos de Cálcio/química , Fontes de Energia Elétrica , Gases/química , Metilaminas/química , Óxidos/química , Energia Solar , Titânio/química , Transição de Fase
17.
Phys Chem Chem Phys ; 16(36): 19206-11, 2014 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-25096582

RESUMO

Formamidinium (FA) lead triiodide perovskite with chlorine addition (NH2CH=NH2PbI(3-x)Clx) is employed as a light harvester in mesoscopic solar cells for the first time. It is demonstrated that a phase-pure FAPbI(3-x)Clx perovskite layer can be synthesized using a one-step solution-process at 140 °C, and the resultant solar cells deliver a maximum power conversion efficiency of 7.51%, which is the most efficient formamidinium-lead-halide perovskite mesoscopic solar cell employing a polymer hole-transporting layer. The effects of the thermal annealing temperature on the quality/morphology of the perovskite layer and the solar cells performance are discussed. The advantages offered by the one-step solution-processing method and the reduced bandgap make FAPbI(3-x)Clx perovskites an attractive choice for future hybrid photovoltaics.


Assuntos
Amidinas/química , Compostos de Cálcio/química , Fontes de Energia Elétrica , Chumbo/química , Óxidos/química , Polímeros/química , Energia Solar , Titânio/química , Microscopia Eletrônica de Varredura , Soluções , Difração de Raios X
18.
J Phys Chem Lett ; 5(19): 3335-9, 2014 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-26278441

RESUMO

A new generation of solid-state photovoltaics is being made possible by the use of organometal-trihalide perovskite materials. While some of these materials are expected to be ferroelectric, almost nothing is known about their ferroelectric properties experimentally. Using piezoforce microscopy (PFM), here we show unambiguously, for the first time, the presence of ferroelectric domains in high-quality ß-CH3NH3PbI3 perovskite thin films that have been synthesized using a new solution-processing method. The size of the ferroelectric domains is found to be about the size of the grains (∼100 nm). We also present evidence for the reversible switching of the ferroelectric domains by poling with DC biases. This suggests the importance of further PFM investigations into the local ferroelectric behavior of hybrid perovskites, in particular in situ photoeffects. Such investigations could contribute toward the basic understanding of photovoltaic mechanisms in perovskite-based solar cells, which is essential for the further enhancement of the performance of these promising photovoltaics.

19.
ACS Appl Mater Interfaces ; 5(1): 128-34, 2013 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23227828

RESUMO

A renewable and superior thermal-resistant cellulose-based composite nonwoven was explored as lithium-ion battery separator via an electrospinning technique followed by a dip-coating process. It was demonstrated that such nanofibrous composite nonwoven possessed good electrolyte wettability, excellent heat tolerance, and high ionic conductivity. The cells using the composite separator displayed better rate capability and enhanced capacity retention, when compared to those of commercialized polypropylene separator under the same conditions. These fascinating characteristics would endow this renewable composite nonwoven a promising separator for high-power lithium-ion battery.


Assuntos
Celulose/química , Fontes de Energia Elétrica , Lítio/química , Técnicas Eletroquímicas , Eletrodos , Íons/química , Nanotecnologia , Polipropilenos/química , Temperatura
20.
ACS Appl Mater Interfaces ; 4(11): 6242-6, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23075280

RESUMO

An inorganic/organic nanocomposite comprised of CuInS(2) nanocrystals and poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (CIS/PEDOT:PSS) was explored as a promising candidate for the counter electrode (CE) in dye-sensitized solar cells (DSCs). Cyclic voltammetry measurements confirmed that this composite electrode exhibited better catalytic activity compared with pristine CuInS2 or PEDOT:PSS electrode. Electrochemical impedance spectroscopy revealed that the composite film constitutes a three-dimensional catalytic network. The DSC using this composite CE can yield 6.50% photoelectric conversion efficiency, which is comparable to that of the conventional platinum CE (6.51%) and better than that of the pristine CuInS2 (5.45%) or PEDOT:PSS (3.22%) electrode.


Assuntos
Corantes/química , Cobre/química , Fontes de Energia Elétrica , Eletrodos , Índio/química , Nanopartículas Metálicas/química , Poliestirenos/química , Selênio/química , Energia Solar , Tiofenos/química , Cristalização/métodos , Desenho de Equipamento , Análise de Falha de Equipamento , Nanopartículas Metálicas/ultraestrutura , Tamanho da Partícula
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