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Omar Allam, Colin Homles, Zev Greenberg, Ki Chul Kim, Seung Soon Jang
In this study, we have developed a protocol for exploring the vast chemical space of possible perovskites and screening the promising candidates. Furthermore, we examined factors that af-fect the band gap energies of perovskites. Goldschmidt tolerance factor and octahedral factor ranges of 0.98 to 1 and 0.45 to 0.7, respectively, are used to filter only highly cubic perovskites that are stable at room temperature. After removing rare or radioactively unstable elements, quan-tum mechanical density functional theory calculations are performed on remaining perovskites to assess whether their electronic properties such as band structure are suitable for solar cell applica-tions...
June 21, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Vikash Kumar Ravi, Rebecca A Scheidt, Jeffrey DuBose, Prashant V Kamat
The suppression of halide ion exchange between CsPbBr3 and CsPbI3 nanocrystals achieved through capping with PbSO4-Oleate has enabled us to deposit different perovskite nanocrystals as aligned arrays on the electrode surfaces without intermixing of species. The electrophoretic deposition of PbSO4-Oleate capped CsPbX3 (X=Cl, Br, I) nanocrystals suspended in hexane solution on mesoscopic TiO2 film allows the design of controlled architecture with single or multiple layers of perovskite films. The hierarchy in the assembly of these nanocrystals is seen first through the linearly organized nanocrystals in hexane followed by the deposition of larger linear rods of length ~500 nm...
June 21, 2018: Journal of the American Chemical Society
Pinar Kaya, Giuliano Gregori, Federico Baiutti, Petar Yordanov, Y Eren Suyolcu, Georg Cristiani, Friederike Wrobel, Eva Benckiser, Bernhard Keimer, Peter A van Aken, Hanns-Ulrich Habermeier, Gennady Logvenov, Joachim Maier
Transition metal oxides exhibit a high potential for application in the field of electronic devices, energy storage, and energy conversion. The ability of building these types of materials by atomic layer-by-layer techniques provides a possibility to design novel systems with favored functionalities. In this study, by means of the atomic layer-by-layer oxide molecular beam epitaxy technique, we designed oxide heterostructures consisting of tetragonal K2 NiF4 -type insulating La2 CuO4 (LCO) and perovskite-type conductive metallic LaNiO3 (LNO) layers with different thicknesses to assess the heterostructure-thermoelectric property-relationship at high temperatures...
June 21, 2018: ACS Applied Materials & Interfaces
V P Sakhnenko, N V Ter-Oganessian
Perovskite-like oxides AB'1/2 B''1/2 O3 with two different cations in the B-sublattice may experience cation order-disorder phase transitions. In many cases the degree of cation ordering can be varied by suitable synthesis conditions or subsequent sample treatment, which has a fundamental impact on the physical properties of such compounds. Therefore, understanding the mechanism of cation order-disorder phase transition and estimation of the phase transition temperature is of paramount importance for tuning of properties of such double perovskites...
June 1, 2018: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
Miguel Anaya, Juan F Galisteo-López, Mauricio Ernesto Calvo, Juan P Espinos, Hernan Miguez
Herein we present a combined study of the evolution of both the photoluminescence and the surface chemical structure of organic metal halide perovskites as environmental oxygen pressure rises from ultra-high vacuum up to a few thousandths of an atmosphere. Analyzing the changes occurring at the semiconductor surface upon photo-excitation under controlled oxygen atmosphere in an X-ray photoelectron spectroscopy (XPS) chamber, we can rationalize the rich variety of photophysical phenomena observed and provide a plausible explanation for light-induced ion migration, one of the most conspicuous and debated concomitant effects detected during photoexcitation...
June 21, 2018: Journal of Physical Chemistry Letters
Timothy Ferreira, Mark D Smith, Hans-Conrad Zur Loye
The compositions of the general formula Ln11- x Sr x Ir4 O24 (Ln = La, Pr, Nd, Sm; 1.37 ≥ x ≥ 2) belonging to a family of A-site cation-deficient double-perovskite-related oxide iridates were grown as highly faceted single crystals from a molten strontium chloride flux. Their structures were determined by single-crystal X-ray diffraction. On the basis of the single-crystal results, additional compositions, Ln9 Sr2 Ir4 O24 (Ln = La, Pr, Nd, Sm), were prepared as polycrystalline powders via solid-state reactions and structurally characterized by Rietveld refinement...
June 21, 2018: Inorganic Chemistry
Yatao Zou, Muyang Ban, Yingguo Yang, Sai Bai, Chen Wu, Yujie Han, Tian Wu, Yeshu Tan, Qi Huang, Xingyu Gao, Tao Song, Qiao Zhang, Baoquan Sun
Solution-processed perovskite light emitting diodes (LEDs) have attracted wide attentions in the past several years. However, the overall efficiency and stability of perovskite-based LEDs remains inferior to those of organic or quantum dot LEDs. Non-radiative charge recombination and the unbalanced charge injection are two critical factors that limit the device efficiency and operational stability of perovskite LEDs. Here, we develop a strategy to modify the interface between hole transport layer and the perovskite emissive layer with an amphiphilic conjugated polymer of poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN)...
June 21, 2018: ACS Applied Materials & Interfaces
Anping Yan, Yunlan Guo, Chao Liu, Zhao Deng, Yi Guo, Xiujian Zhao
Topotactic anion exchange has been developed to tune the composition and band gap energies of cesium lead halide (CsPbX3 ) perovskite nanocrystals (NCs). However, current anion exchange methods either require harsh conditions or take a long time to realize substantial substitution. Here, we present a method to modulate the composition of colloidal CsPbBr3 NCs through ultrasonication-assisted anion exchange with CsX (X = Cl, I) solution. Efficient anion exchange of CsPbBr3 NCs with Cl- or I- is realized with substitution ratio up to 93% and preservation of the pristine shape and structure of CsPbBr3 NCs...
June 20, 2018: Nanoscale Research Letters
Xiaoqing Chen, Yasuhiro Shirai, Masatoshi Yanagida, Kenjiro Miyano
We studied perovskite photovoltaic devices with intensity-modulated photovoltage spectroscopy. Two coexisting relaxation times are found in accordance with the results of previous impedance spectroscopy (IS) measurements. The slower time constant is independent of the light power while the faster one is inversely proportional to the light power. We employed the surface polarization picture used in the IS analysis augmented by a plausible assumption that the surface polarization is proportional to the light intensity to explain the inverse power dependence of the fast time constant...
June 21, 2018: Physical Chemistry Chemical Physics: PCCP
Yan Gao, Liyun Zhao, Qiuyu Shang, Yangguang Zhong, Zhen Liu, Jie Chen, Zhepeng Zhang, Jia Shi, Wenna Du, Yanfeng Zhang, Shulin Chen, Peng Gao, Xinfeng Liu, Xina Wang, Qing Zhang
1D nanowires of all-inorganic lead halide perovskites represent a good architecture for the development of polarization-sensitive optoelectronic devices due to their high absorption efficient, emission yield, and dielectric constants. However, among as-fabricated perovskite nanowires with the lateral dimensions of hundreds nanometers so far, the optical anisotropy is hindered and rarely explored owing to the invalidating of electrostatic dielectric mismatch in the physical dimensions. Here, well-aligned CsPbBr3 and CsPbCl3 nanowires with thickness T down to 15 and 7 nm, respectively, are synthesized using a vapor phase van der Waals epitaxial method...
June 19, 2018: Advanced Materials
Xiao Wang, Ye Han, Xiaojie Song, Weihui Liu, Yinxi Jin, Wentao Liu, Hongzhi Cui
ABO3 perovskite-type LaCoO3, LaCo0.5Fe0.5O3, LaCo0.5Ni0.5O3, and LaCo0.5Mn0.5O3 complex oxides were synthesized using the sol-gel method. The microstructure and the thermal expansion behavior of the oxides were investigated. Insights into phonon dispersion and the effects of doped transition metals on thermal expansion were obtained by first-principles calculations based on density functional theory. Thermal expansion coefficients (TECs) at finite temperatures were obtained by quasi harmonic approximation. B-site doping was found to reduce the size of the crystalline grains and the TECs of perovskite compounds...
June 20, 2018: Physical Chemistry Chemical Physics: PCCP
Yue Wu, David M Halat, Fengxia Wei, Trevor Binford, Ieuan D Seymour, Michael W Gaultois, Sammy Shaker, John Wang, Clare P Grey, Anthony K Cheetham
Following the recent discovery of a new family of hybrid ABX3 perovskites where X = (H2POO)- (hypophosphite), we show a facile synthesis for mixed X-site formate perovskites of composition [GUA]Mn(HCOO)3-x(H2POO)x. We report two crystallographically distinct, partially ordered intermediate phases with x = 0.84 and 1.53, corresponding to ca. 30 and 50 mole % hypophosphite respectively. These phases are characterised by single-crystal XRD and solid-state NMR spectroscopy, and their magnetic properties are reported...
June 19, 2018: Chemistry: a European Journal
Meng Xiao, Li Zhao, Min Geng, Yanyan Li, Binghai Dong, Zuxun Xu, Li Wan, Wenlu Li, Shimin Wang
The perovskite layer is a crucial component influencing high-performance perovskite solar cells (PSCs). In the one-step solution method, anti-solvents are important for obtaining smooth and uniform perovskite active layers. This work explored the effect of various anti-solvents on the preparation of triple cation perovskite active layers. In general, anti-solvents with low dielectric constants, low polarity, and low boiling point are suitable for the preparation of perovskite films. Microstructural and elemental analyses of the perovskite films were systematically conducted by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy...
June 19, 2018: Nanoscale
Navendu Mondal, Apurba De, Anunay Samanta
Recent studies show that perovskite (ABX3 type) nanocrystals comprising mixed A or B cation and/or mixed halide (X) are more stable and efficient materials for photovoltaic applications than their respective pure forms. Herein we report how doping of small quantity of formamidinium and/or chloride ion influences the single and multi-exciton dynamics of CsPbI3 nanocrystals. With the help of ultrafast pump-probe spectroscopic measurements we show that chloride doping can enhance the biexciton lifetime of the system significantly by slowing down the Auger recombination (AR) process...
June 19, 2018: Journal of Physical Chemistry Letters
Linxing Zhang, Bo Li, Jifeng Yuan, Mengru Wang, Ting Shen, Fei Huang, Wen Wen, Guozhong Cao, Jianjun Tian
Inorganic halide perovskites exhibit significant photovoltaic performance due to their structural stability and high open-circuit voltage ( Voc ). Herein, a general strategy of solution engineering has been implemented to enable a wide solution-processing window for high Voc (∼1.3 V) and power conversion efficiency (PCE, ∼12.5%). We introduce a nontoxic solvent of dimethyl sulfoxide (DMSO) and an assisted heating process in the fabrication of CsPbI2 Br (CPI2) to control the improved crystallization. A wide solution-processing window including a wide range of solvent components and solute concentrations has been realized...
June 20, 2018: Journal of Physical Chemistry Letters
Minkyu Kyeong, Jinho Lee, Kwanghee Lee, Sukwon Hong
Recently perovskite solar cells (PSCs) have emerged as an excellent photovoltaic device owing to the outstanding power conversion efficiency (PCE). Nevertheless, device instability remains a critical issue in this field. To overcome device instability without deteriorating PCE, dopant-free hole transporting materials (HTMs) is needed to separate the air-sensitive perovskite layer from extrinsic factors which induce its degradation. Herein we developed novel conjugate polymers of benzo[1,2-b:4,5-b']dithiophene (BDT) and 4,4-difluoro-4-bora-3a,4a-diaza- s-indacene (BODIPY) for use as HTMs without dopants...
June 19, 2018: ACS Applied Materials & Interfaces
Hanna L B Boström, Mark S Senn, Andrew L Goodwin
The central goal of crystal engineering is to control material function via rational design of structure. A particularly successful realisation of this paradigm is hybrid improper ferroelectricity in layered perovskite materials, where layering and cooperative octahedral tilts combine to break inversion symmetry. However, in the parent family of inorganic ABX3 perovskites, symmetry prevents hybrid coupling to polar distortions. Here, we use group-theoretical analysis to uncover a profound enhancement of the number of improper ferroelectric coupling schemes available to molecular perovskites...
June 18, 2018: Nature Communications
Fanmao Liu, Ignasi Fina, Guillaume Sauthier, Florencio Sanchez, Andrew M Rappe, Josep Fontcuberta
Ferroelectric perovskites hold promise of enhanced photovoltaic efficiency and photocatalytic activity. Consequently, the photoresponse of oxide ferroelectric thin films is an active field of research. In electrode/ferroelectric/electrode devices, internal charge in the ferroelectric, free charge in the electrodes, and buried adsorbates at interfaces combine to screen the ferroelectric polarization and to stabilize the polar state. Under illumination, photo-induced carriers and photo-dissociated adsorbates may disrupt the screening equilibrium, modifying the switchable polarization and altering its expected benefits...
June 18, 2018: ACS Applied Materials & Interfaces
Chia-Chih Chang, Jhih-Hao Tao, Che-En Tsai, Yen-Ju Cheng, Chain-Shu Hsu
The device performance of inverted organic metallohalide perovskite solar cells (OMPSCs) is optimized via tailoring the electrode surfaces with electron- and hole-transporting materials. This work demonstrates the fabrication of PEDOT:PSS-free OMPSCs using a hole-transporting composite material consisting of bilayered vanadium oxide (VO x ) and a thermally cross-linked triarylamine-based material X-DVTPD, which contributes to higher Voc and Jsc values. The hydrophobicity of X-DVTPD resulted in the formation of large perovskite crystals and enhanced the stability of OMPSCs...
June 18, 2018: ACS Applied Materials & Interfaces
Loredana Protesescu, Sergii Yakunin, Olga Nazarenko, Dmitry N Dirin, Maksym V Kovalenko
Lead halide perovskites of APbX3 type [A = Cs, formamidinium (FA), methylammonium; X = Br, I] in the form of ligand-capped colloidal nanocrystals (NCs) are widely studied as versatile photonic sources. FAPbBr3 and CsPbBr3 NCs have become promising as spectrally narrow green primary emitters in backlighting of liquid-crystal displays (peak at 520-530 nm, full width at half-maximum of 22-30 nm). Herein, we report that wet ball milling of bulk APbBr3 (A = Cs, FA) mixed with solvents and capping ligands yields green luminescent colloidal NCs with a high overall reaction yield and optoelectronic quality on par with that of NCs of the same composition obtained by hot-injection method...
March 23, 2018: ACS applied nano materials
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