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1.
Angew Chem Int Ed Engl ; 59(4): 1469-1473, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31680389

RESUMO

The reduced dimension perovskite including 2D perovskites are one of the most promising strategies to stabilize lead halide perovskite. A mixed-cation 2D perovskite based on a steric phenyltrimethylammonium (PTA) cation is presented. The PTA-MA mixed-cation 2D perovskite of PTAMAPbI4 can be formed on the surface of MAPbI3 (PTAI-MAPbI3 ) by controllable PTAI intercalation by either spin coating or soaking. The PTAMAPbI4 capping layer can not only passivate PTAI-MAPbI3 perovskite but also act as MA+ locker to inhibit MAI extraction and significantly enhance the stability. The highly stable PTAI-MAPbI3 based perovskite solar cells exhibit a reproducible photovoltaic performance with a champion PCE of 21.16 %. Such unencapsulated devices retain 93 % of initial efficiency after 500 h continuous illumination. This steric mixed-cation 2D perovskite as MA+ locker to stabilize the MAPbI3 is a promising strategy to design stable and high-performance hybrid lead halide perovskites.

2.
Angew Chem Int Ed Engl ; 58(46): 16691-16696, 2019 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-31538395

RESUMO

The controllable growth of CsPbI3 perovskite thin films with desired crystal phase and morphology is crucial for the development of high efficiency inorganic perovskite solar cells (PSCs). The role of dimethylammonium iodide (DMAI) used in CsPbI3 perovskite fabrication was carefully investigated. We demonstrated that the DMAI is an effective volatile additive to manipulate the crystallization process of CsPbI3 inorganic perovskite films with different crystal phases and morphologies. The thermogravimetric analysis results indicated that the sublimation of DMAI is sensitive to moisture, and a proper atmosphere is helpful for the DMAI removal. The time-of-flight secondary ion mass spectrometry and nuclear magnetic resonance results confirmed that the DMAI additive would not alloy into the crystal lattice of CsPbI3 perovskite. Moreover, the DMAI residues in CsPbI3 perovskite can deteriorate the photovoltaic performance and stability. Finally, the PSCs based on phenyltrimethylammonium chloride passivated CsPbI3 inorganic perovskite achieved a record champion efficiency up to 19.03 %.

3.
Science ; 365(6453): 591-595, 2019 08 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395783

RESUMO

Although ß-CsPbI3 has a bandgap favorable for application in tandem solar cells, depositing and stabilizing ß-CsPbI3 experimentally has remained a challenge. We obtained highly crystalline ß-CsPbI3 films with an extended spectral response and enhanced phase stability. Synchrotron-based x-ray scattering revealed the presence of highly oriented ß-CsPbI3 grains, and sensitive elemental analyses-including inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry-confirmed their all-inorganic composition. We further mitigated the effects of cracks and pinholes in the perovskite layer by surface treating with choline iodide, which increased the charge-carrier lifetime and improved the energy-level alignment between the ß-CsPbI3 absorber layer and carrier-selective contacts. The perovskite solar cells made from the treated material have highly reproducible and stable efficiencies reaching 18.4% under 45 ± 5°C ambient conditions.

4.
J Phys Chem A ; 123(13): 2674-2678, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30865453

RESUMO

Organometallic halide perovskite solar cells such as MAPbI3 have shown great promise as a low-cost, high-efficiency photovoltaic candidate. Recent studies demonstrated that by substituting an appropriate amount I ions of MAPbI3 with Br ions, the device performance parameters, such as moisture stability or power conversion efficiency, can be further optimized. In this study, using time-resolved optical reflectivity to track the carrier dynamics in MAPb(I1- xBr x)3 films with different Br contents, we found that photocarriers in MAPb(I1- xBr x)3 films with x = 0.01 and 0.02 diffuse much faster than those in films with other Br contents. We suggest that the faster charge carrier diffusion benefits from larger crystal grain size. As a result, this suppresses electron and hole recombination and increases the carrier extraction efficiency, in agreement with the higher power conversion efficiency reported previously.

5.
J Am Chem Soc ; 140(39): 12345-12348, 2018 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-30247030

RESUMO

The all-inorganic α-CsPbI3 perovskite with the most suitable band gap faces serious challenges of low phase stability and high moisture sensitivity. We discover that a simple phenyltrimethylammonium bromide (PTABr) post-treatment could achieve a bifunctional stabilization including both gradient Br doping (or alloying) and surface passivation. The PTABr treatment on CsPbI3 only induces less than 5 nm blue shift in UV-vis absorbance but significantly stabilize the perovskite phase with much better stability. Finally, the highly stable PTABr treated CsPbI3 based perovskite solar cells exhibit a reproducible photovoltaic performance with a champion efficiency up to 17.06% and stable output of 16.3%. Therefore, this one-step bifunctional stabilization of perovskite through gradient halide doping and surface organic cation passivation presents a novel and promising strategy to design stable and high performance all-inorganic lead halide.

6.
Chem Commun (Camb) ; 54(70): 9809-9812, 2018 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-30106083

RESUMO

All-inorganic halide perovskites without volatile components have great potential for long term thermal stability. However, the phase stability of all-inorganic perovskites is sensitive to moisture and has been seldom studied. In this work, the phase stability of α-CsPbI2Br was studied in different relative humidity conditions. The moisture resistance of α-CsPbI2Br can be significantly enhanced by using a polymer or organic molecule capping layer including Spiro-MeOTAD. Although an all-inorganic CsPbI2Br perovskite based device using the typical Li salt doped Spiro-MeOTAD layer could offer an efficiency up to 12.6%, it exhibited even worse moisture resistance than a bare perovskite film under the same ambient conditions. This unusual phenomenon is ascribed to the hygroscopic properties of Li-TFSI inducing moisture sensitive phase degradation. Therefore, it is desirable to decrease the amount of, or avoid the Li salt, as a dopant for stable all-inorganic perovskite solar cells with balanced stability and high performance.

7.
J Am Chem Soc ; 140(37): 11811-11819, 2018 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-30157629

RESUMO

In this work, the spatially dependent recombination kinetics of mixed-halide hybrid perovskite CH3NH3Pb(Br1- xCl x)3 (0 ≤ x ≤ 0.19) single crystals are investigated using time-resolved photoluminescence spectroscopy with one- and two-photon femtosecond laser excitation. The introduction of chloride by substituting a fraction of the bromide leads to a decreased lattice constant compared to pure bromide perovskite ( x = 0) and a higher concentration of surface defects. The measured kinetics under one-photon excitation (1PE) shows that increasing the chloride addition quenches the photoluminescence (PL) lifetimes, due to substitution-induced surface defects. In stark contrast, upon 2PE, the PL lifetimes measured deeper in the bulk become longer with increasing chloride addition, until the halide substitution reaches the critical concentration of ∼19%. At x = 19% Cl concentration, a significant reversal of this behavior is observed indicating a change in crystal structure beyond the continuous trends observed at lower percentages of halide substitution ( x ≤ 11%). The observed opposing trends, based on 1PE versus 2PE, highlight a dichotomy between extrinsic (surface) and intrinsic (bulk) effects of chloride substitution on the carrier dynamics in lead bromide perovskites. We discuss the physical relation between halide exchange and bulk carrier lifetimes in CH3NH3PbBr3 in terms of the Rashba effect. We propose that the latter is suppressed at the surface due to disorder in the alignment of the MA and that it increases in the bulk with Cl concentration because of the reduction in lattice parameters, which compresses the space available for the MA orientational degrees of freedom.

8.
Sci Adv ; 3(9): e1700841, 2017 09.
Artigo em Inglês | MEDLINE | ID: mdl-28975149

RESUMO

Among various all-inorganic halide perovskites exhibiting better stability than organic-inorganic halide perovskites, α-CsPbI3 with the most suitable band gap for tandem solar cell application faces an issue of phase instability under ambient conditions. We discovered that a small amount of two-dimensional (2D) EDAPbI4 perovskite containing the ethylenediamine (EDA) cation stabilizes the α-CsPbI3 to avoid the undesirable formation of the nonperovskite δ phase. Moreover, not only the 2D perovskite of EDAPbI4 facilitate the formation of α-CsPbI3 perovskite films exhibiting high phase stability at room temperature for months and at 100°C for >150 hours but also the α-CsPbI3 perovskite solar cells (PSCs) display highly reproducible efficiency of 11.8%, a record for all-inorganic lead halide PSCs. Therefore, using the bication EDA presents a novel and promising strategy to design all-inorganic lead halide PSCs with high performance and reliability.

9.
ChemSusChem ; 10(11): 2365-2369, 2017 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-28421678

RESUMO

The chloride-doped CH3 NH3 PbI3-x Clx perovskite has attracted great attention owing to clear performance enhancement by using a Cl additive and by the controversial arguments on Cl function and the mechanism behind it. Herein, a series of CH3 NH3 PbI3-x Clx perovskites with various Cl content was prepared through a gas/solid reaction between CH3 NH2 gas and HPbI3-x Clx (x=0-1). The small amount of Cl doping in CH3 NH3 PbI3-x Clx (x=0.05) could lead to band gap broadening and significantly increase the perovskite grain size, and the phase-pure CH3 NH3 PbI2.95 Cl0.05 perovskites exhibited up to 17.44 % efficiency. For Cl contents higher than 0.1 (x>0.1), CH3 NH3 PbCl3 formed and coexisted with CH3 NH3 PbI3-x Clx , and CH3 NH3 PbCl3 could help to improve the thermal stability of CH3 NH3 PbI3-x Clx . However, the excessive co-existing wide-band-gap CH3 NH3 PbCl3 perovskites would inhibit the electron transfer and lead to a deterioration of photovoltaic performance.


Assuntos
Fontes de Energia Elétrica/normas , Energia Solar , Compostos de Cálcio , Cloretos , Elétrons , Chumbo , Óxidos , Titânio
10.
Angew Chem Int Ed Engl ; 55(43): 13460-13464, 2016 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-27667326

RESUMO

High-quality phase-pure MA1-x FAx PbI3 planar films (MA=methylammonium, FA=formamidinium) with extended absorption and enhanced thermal stability are difficult to deposit by regular simple solution chemistry approaches owing to crystallization competition between the easy-to-crystallize but unwanted δ-FAPbI3 /MAPbI3 and FAx MA1-x PbI3 requiring rigid crystallization conditions. Here A 2D-3D conversion to transform compact 2D mixed composition HMA1-x FAx PbI3 Cl perovskite precursor films into 3D MA1-x FAx PbI3 (x=0.1-0.9) perovskites is presented. The designed Cl/I and H/FA(MA) ion exchange reaction induced fast transformation of compact 2D perovskite film, helping to form the phase-pure and high quality MA1-x FAx PbI3 without δ-FAPbI3 and MAPbI3 impurity. In all, we successfully developed a facile one-step method to fabricate high quality phase-pure MA1-x FAx PbI3 (x=0.1-0.9) perovskite films by 2D-3D conversion of HMA1-x FAx PbI3 Cl perovskite. This 2D-3D conversion is a promising strategy for lead halide perovskite fabrication.

11.
Chem Commun (Camb) ; 52(74): 11080-3, 2016 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-27541585

RESUMO

We demonstrate a new strategy for the in situ formation of highly luminescent CH3NH3PbBr3 perovskite planar film via the reaction between PbBr2 and methylamine gas. The obtained CH3NH3PbBr3 perovskite planar film exhibited similar quantum confinement to solution chemistry synthesized colloidal CH3NH3PbBr3 quantum dots. Such quantum confinement was realized by a PbOx/Pb(OH)2 framework, which is a by-product formed in situ from the reaction of PbBr2 and methylamine gas under ambient conditions.

12.
Nat Commun ; 7: 12305, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27477212

RESUMO

Organometallic halide perovskite solar cells (PSCs) have shown great promise as a low-cost, high-efficiency photovoltaic technology. Structural and electro-optical properties of the perovskite absorber layer are most critical to device operation characteristics. Here we present a facile fabrication of high-efficiency PSCs based on compact, large-grain, pinhole-free CH3NH3PbI3-xBrx (MAPbI3-xBrx) thin films with high reproducibility. A simple methylammonium bromide (MABr) treatment via spin-coating with a proper MABr concentration converts MAPbI3 thin films with different initial film qualities (for example, grain size and pinholes) to high-quality MAPbI3-xBrx thin films following an Ostwald ripening process, which is strongly affected by MABr concentration and is ineffective when replacing MABr with methylammonium iodide. A higher MABr concentration enhances I-Br anion exchange reaction, yielding poorer device performance. This MABr-selective Ostwald ripening process improves cell efficiency but also enhances device stability and thus represents a simple, promising strategy for further improving PSC performance with higher reproducibility and reliability.

13.
Phys Chem Chem Phys ; 18(27): 18112-8, 2016 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-27327514

RESUMO

Organolead halide perovskites exhibit superior photoelectric properties, which have given rise to the perovskite-based solar cells whose power conversion efficiency has rapidly reached above 20% in the past few years. However, perovskite-based solar cells have also encountered problems such as current-voltage hysteresis and degradation under practical working conditions. Yet investigations into the intrinsic chemical nature of the perovskite material and its role on the performance of the solar cells are relatively rare. In this work, Raman spectroscopy is employed together with CASTEP calculations to investigate the organic-inorganic interactions in CH3NH3PbI3 and CH3NH3PbBr3-xClx perovskite single crystals with comparison to those having ammonic acid as the cations. For Raman measurements of CH3NH3PbI3, a low energy line of 1030 nm is used to avoid excitation of strong photoluminescence of CH3NH3PbI3. Raman spectra covering a wide range of wavenumbers are obtained, and the restricted rotation modes of CH3-NH3(+) embedded in CH3NH3PbBr3 (325 cm(-1)) are overwhelmingly stronger over the other vibrational bands of the cations. However, the band intensity diminishes dramatically in CH3NH3PbBr3-xClx and most of the bands shift towards high frequency, indicating the interaction with the halides. The details of such an interaction are further revealed by inspecting the band shift of the restricted rotation mode as well as the C-N, NH3(+) and CH3 stretching of the CH3NH3(+) as a function of Cl composition and length of the cationic ammonic acids. The results show that the CH3NH3(+) interacts with the PbX3(-) octahedral framework via the NH3(+) end through N(+)-HX hydrogen bonding whose strength can be tuned by the composition of halides but is insensitive to the size of the organic cations. Moreover, an increase of the Cl content strengthens the hydrogen bonding and thus blueshifts the C-N stretching bands. This is due to the fact that Cl is more electronegative than Br and an increase of the Cl content decreases the lattice constant of the perovskite. The findings of the present work are valuable in understanding the role of cations and halides in the performance of MAPbX3-based perovskite solar cells.

14.
Nano Lett ; 15(6): 3959-63, 2015 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-25996160

RESUMO

We demonstrate a facile morphology-controllable sequential deposition of planar CH3NH3PbI3 (MAPbI3) film by using a novel volume-expansion-adjustable PbI2·xMAI (x: 0.1-0.3) precursor film to replace pure PbI2. The use of additive MAI during the first step of deposition leads to the reduced crystallinity of PbI2 and the pre-expansion of PbI2 into PbI2·xMAI with adjustable morphology, which result in about 10-fold faster formation of planar MAPbI3 film (without PbI2 residue) and thus minimize the negative impact of the solvent isopropanol on perovskites during the MAI intercalation/conversion step. The best efficiency obtained for a planar perovskite solar cell based on PbI2·0.15MAI is 17.22% (under one sun illumination), which is consistent with the stabilized maximum power output at an efficiency of 16.9%.

15.
Chem Commun (Camb) ; 51(37): 7820-3, 2015 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-25853846

RESUMO

We demonstrate a facile synthetic approach for preparing mixed halide perovskite (CH3NH3)Pb(Br1-xClx)3 single crystals by the solvothermal growth of stoichiometric PbBr2 and [(1 - y)CH3NH3Br + yCH3NH3Cl] DMF precursor solutions. The band gap of (CH3NH3)Pb(Br1-xClx)3 single crystals increased and the unit cell dimensions decreased with an increase in Cl content x, consistent with previous theoretical predictions. Interestingly, the Cl/Br ratio in the (CH3NH3)Pb(Br1-xClx)3 single crystals is larger than that of the precursor solution, suggesting an unusual crystal growth mechanism.

16.
J Colloid Interface Sci ; 402: 279-83, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23639220

RESUMO

A ternary assembly consisting of reduced graphene oxide (RGO), Ag nanoparticles, and polystyrene (PS) microsphere was prepared in aqueous solution by an electrostatic assembly combined with one-step reduction process. The composition and structure of the assembly (PS microsphere/RGO/Ag) were characterized by powder X-ray diffraction, transmission electron microscope, scanning electron microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy. The interactions among RGO, Ag nanoparticles, and PS microsphere were investigated by surface enhanced Raman scattering spectroscopy. The results showed that there existed strong interactions among RGO, Ag nanoparticles, and PS microsphere. Importantly, the assembly showed high heat stability and good dispersion in water.

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