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Wei-Wei Peng, Robert Tétot, Gang Niu, Emilie Amzallag, Bertrand Vilquin, Jean-Blaise Brubach, Pascale Roy
Due to the remarkable possibilities of epitaxially growing strontium titanate (SrTiO3 or STO) on silicon, this oxide is widely used as a buffer layer for integrating other perovskite oxides which allows for the development of various functional electronic devices on silicon. Moreover, STO is known to be an incipient ferroelectric in bulk but may become ferroelectric when in the form of strained ultrathin films. Given the importance of the potential applications for electronics if this property is demonstrated, we performed a spectroscopic study of STO on Si(001) templates coupling experimental and ab initio investigations...
May 19, 2017: Scientific Reports
Shaocong Hou, Yuzheng Guo, Yuguo Tang, Qimin Quan
Lead halide perovskites have emerged as low-cost, high-performance optical and optoelectronic materials, however, their material stability has been a limiting factor for broad applications. Here, we demonstrate stable core-shell colloidal perovskite nanocrystals using a novel, facile and low-cost co-polymer templated synthesis approach. The block co-polymer serves as a confined nano-reactor during perovskite crystallization and passivates the perovskite surface by forming a multidentate capping shell, thus significantly improving its photo-stability in polar solvents...
May 19, 2017: ACS Applied Materials & Interfaces
Chongwen Li, Yuanyuan Zhou, Li Wang, Yue Chang, Yingxia Zong, Lioz Etgar, Guanglei Cui, Nitin P Padture, Shuping Pang
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...
May 19, 2017: Angewandte Chemie
Yongzhen Wu, Fengxian Xie, Han Chen, Xudong Yang, Huimin Su, Molang Cai, Zhongmin Zhou, Takeshi Noda, Liyuan Han
Solution-processed perovskite (PSC) solar cells have achieved extremely high power conversion efficiencies (PCEs) over 20%, but practical application of this photovoltaic technology requires further advancements on both long-term stability and large-area device demonstration. Here, an additive-engineering strategy is developed to realize a facile and convenient fabrication method of large-area uniform perovskite films composed of large crystal size and low density of defects. The high crystalline quality of the perovskite is found to simultaneously enhance the PCE and the durability of PSCs...
May 19, 2017: Advanced Materials
Barry McKenna, Rachel C Evans
Single-junction photovoltaic devices exhibit a bottleneck in their efficiency due to incomplete or inefficient harvesting of photons in the low- or high-energy regions of the solar spectrum. Spectral converters can be used to convert solar photons into energies that are more effectively captured by the photovoltaic device through a photoluminescence process. Here, recent advances in the fields of luminescent solar concentration, luminescent downshifting, and upconversion are discussed. The focus is specifically on the role that materials science has to play in overcoming barriers in the optical performance in all spectral converters and on their successful integration with both established (e...
May 19, 2017: Advanced Materials
Kosuke Beppu, Saburo Hosokawa, Takuya Shibano, Akito Demizu, Kazuo Kato, Kenji Wada, Hiroyuki Asakura, Kentaro Teramura, Tsunehiro Tanaka
This study proves that a small amount of Pd loading (1 wt%) on Sr3Fe2O7-δ can dramatically enhance the oxygen-storage properties of Sr3Fe2O7-δ. The topotactic oxygen intake and release between Sr3Fe2O6.75 and Sr3Fe2O6 takes place in response to gas switching between an O2 flow and H2 flow, regardless of the presence or absence of Pd loading. The effect of Pd loading is significant for the oxygen-release process under H2 atmosphere; that is, highly dispersed Pd metal nanoparticles sized less than 1 nm formed on Pd/Sr3Fe2O7-δ to promote H2 dissociation, resulting in the improvement of the oxygen-release temperature and rate...
May 19, 2017: Physical Chemistry Chemical Physics: PCCP
Kezhao Du, Weiwei Meng, Xiaoming Wang, Yanfa Yan, David B Mitzi
The double perovskite family, A2MIMIIIX6, represents a promising route to overcome the lead toxicity issue confronting current photovoltaic (PV) standout, CH3NH3PbI3. Given the generally large indirect bandgap within most known double perovskites, bandgap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs2AgBiBr6 as host, we demonstrate bandgap engineering through alloying of InIII/SbIII. Cs2Ag(Bi1-xMx)Br6 (M = In, Sb) accommodates up to 75% InIII with increased bandgap, and up to 37...
May 18, 2017: Angewandte Chemie
Michel Pouchard
Paul Hagenmuller, honorary professor at the Université de Bordeaux, passed away at the age of 95 on January 7, 2017. Hagenmuller was one of the founders of solid-state chemistry at the interface between chemistry, physics, and material science, with contributions including high oxidation states in transition metal oxides, magnesium hydride for hydrogen-storage applications, and synthesis of copper perovskites.
May 19, 2017: Angewandte Chemie
Peng Liu, Xianxiong He, Jiahuan Ren, Qing Liao, Jiannian Yao, Hongbing Fu
Fabrication of semiconductor nanowire laser arrays with multi-color outputs are very challenging, owing to difficulties in direct monolithic growth and patterning of III-V semiconductors on silicon substrates. Recently, methylammonium lead halide perovskites (MAPbX3, X = Cl, Br, I) have emerged as an important class of high-performance solution-processed optoelectronic materials. Here, we combined the 'top-down' fabricated polydimethylsiloxane (PDMS) rectangular groove-template (RGT) with the 'bottom-up' solution self-assembly together to prepare large-scale perovskite nanowire (PNW) arrays...
May 18, 2017: ACS Nano
Jie Ma, Lin-Wang Wang
CH3NH3PbI3 is one of the most promising candidates for cheap and high-efficiency solar cells. One of its unique features is the long carrier diffusion length (> 100 μm), but its carrier mobility is rather modest. The nature of the mobility is unclear. Here, using non-adiabatic wave function dynamics simulations, we show that the random rotations of the CH3NH3 cations play an important role in the carrier mobility. Our previous work showed that the electron and hole wave functions were localized and spatially separated due to the random orientations of the CH3NH3 cations in the tetragonal phase...
May 18, 2017: Nano Letters
Sergey V Ovsyannikov, Elena Bykova, Anna Pakhomova, Denis P Kozlenko, Maxim Bykov, Sergey E Kichanov, Natalia V Morozova, Igor V Korobeinikov, Fabrice Wilhelm, Andrei Rogalev, Alexander A Tsirlin, Alexander V Kurnosov, Yury G Zainulin, Nadezda I Kadyrova, Alexander P Tyutyunnik, Leonid Dubrovinsky
We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo3V4O12 double perovskite with the high-spin (HS) Co(2+) ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co(2+) ions in the direction perpendicular to the oxygen planes...
May 18, 2017: Inorganic Chemistry
Jinwen Shi, Yazhou Zhang, Zhaohui Zhou, Yixiang Zhao, Jingyuan Liu, Hongbing Liu, Xiang Liao, Yuchao Hu, Daming Zhao, Shaohua Shen
(LaTiO2N)1-x(LaCrO3)x continuous solid solutions with an orthorhombic-phase ABX3 perovskite structure and with varied LaCrO3 contents (0 ≤ x ≤ 1) were synthesized by a polymerized complex method followed by a post-treatment process of nitridation for the first time. Visible-light-driven photocatalytic H2-evolution activities of the solid solutions gradually increased with the increase of x from 0.0 to 0.3, and then sharply decreased with the further increase of x from 0.3 to 1.0. With the increase of x, on the one hand, the narrowed bandgaps of solid solutions would enhance the generation of charge carriers and the increased lattice distortion of solid solutions could promote the separation and migration of charge carriers, thus mainly contributing to the improvement of photocatalytic activities; on the other hand, the lowered CBMs of solid solutions would reduce the driving force for reducing H2O to H2 and the decreased surface areas of solid solutions would weaken the adsorption of reactants and reduce the reactive sites, thereby resulting in the deterioration of photocatalytic activities...
May 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Jianbo Li, Yingli Shen, Yucheng Liu, Feng Shi, Xiaodong Ren, Tianqi Niu, Kui Zhao, Shengzhong Frank Liu
Methylammonium lead halide perovskite is emerged as a new class of low-temperature-processed high-performance semiconductors for optoelectronics, but with photoresponse limited to the UV-visible region and low environmental stability. Herein, we report a flexible planar photodetector based on MAPbI3 microarrays integrated with NaYF4:Yb/Er upconversion nanoparticles (UCns) that offers promise for future high performance and long-term stability operation. The promise derives from the confluence of several factors, including significantly enhanced photons absorption in the visible spectrum, efficient energy transition in the NIR region, and inhibition of water attack by the hydrophobic UCns capping layer...
May 18, 2017: ACS Applied Materials & Interfaces
Xiaoyuan Liu, Xiaolu Zheng, Yulong Wang, Zhiliang Chen, Fang Yao, Qi Zhang, Guojia Fang, Zhi-Kuan Chen, Wei Huang, ZongXiang Xu
Solution-processed hole transporting materials (HTMs) that are dopant-free show promise for use in low-cost, high performance perovskite solar cells (PSCs). The highest efficiency PSCs use organic HTMs, many of which have low mobilities and so require doping, which lowers the device stability. Additionally, these materials are not easily scaled because they often require complicated synthesis. Two novel HTMs (IDT-TPA and IDTT-TPA) were synthesized, which contained either an extended fused-ring indacenodithiophene (IDT) or indacenodithienothiophene (IDTT) core and strong electron donating methoxytriphenylamine (TPA) groups as the end-capping units...
May 18, 2017: ChemSusChem
Longfei Ruan, Wei Shen, Aifei Wang, Qingwen Zhou, Huigang Zhang, Zhengtao Deng
Lead halide perovskites exhibit outstanding optoelectronic and optical properties. However, some applications of perovskites are hindered by their instability in polar environments; thus, how to balance stability with conductivity is a great challenge. Here, we report a new approach of using X-type ligands to address this issue. Surface treatments containing multi-step ligand exchanges and ion filling were necessary to obtain X-type ligand-protected perovskites. Performances of this material show that: (1) the crystal structure of perovskites is stable in ethanol; (2) surface defects can be fixed by a photoactivation process and photoluminescence intensity can be enhanced to 136%; and (3) electronic devices fabricated from such materials show stabilility even after washing with ethanol...
May 18, 2017: Nanoscale
Jungang Hou, Shuyan Cao, Yunzhen Wu, Zhanming Gao, Fei Liang, Yiqing Sun, Zheshuai Lin, Licheng Sun
Inorganic perovskite quantum dots as optoelectronic materials have attracted enormous attention in light harvesting and emitting devices. However, photocatalytic conversion based on inorganic perovskite halides has not been reported. Herein, we have synthesized colloidal quantum dots (QDs, 3-12 nm) of cesium lead halide perovskites (CsPbBr3) as newcomer photocatalytic materials. The bandgap energies and photoluminescence (PL) spectra are tunable over the visible spectral region by quantum size effects on an atomic scale...
May 17, 2017: Chemistry: a European Journal
Longbin Qiu, Luis K Ono, Yan Jiang, Matthew R Leyden, Sonia R Raga, Shenghao Wang, Yabing Qi
The rapid rise of power conversion efficiency (PCE) of low cost organometal halide perovskite solar cells suggests that these cells are a promising alternative to conventional photovoltaic technology. However, anomalous hysteresis and unsatisfactory stability hinder the industrialization of perovskite solar cells. Interface engineering is of importance for the fabrication of highly stable and hysteresis free perovskite solar cells. Here we report that a surface modification of the widely used TiO2 compact layer can give insight into interface interaction in perovskite solar cells...
May 17, 2017: Journal of Physical Chemistry. B
Mingming Chen, Xin Shan, Thomas Geske, Junqiang Li, Zhibin Yu
Ion migration has been commonly observed as a detrimental phenomenon in organometal halide perovskite semiconductors, causing the measurement hysteresis in solar cells and ultra-short operation lifetimes in light-emitting diodes. In this work, ion migration is utilized for the formation of a p-i-n junction at ambient temperature in single-crystalline organometal halide perovskites. The junction is subsequently stabilized by quenching the ionic movement at a low temperature. Such a strategy of manipulating the ion migration has led to efficient single-crystalline light-emitting diodes that emit 2...
May 17, 2017: ACS Nano
Yahui Li, Zhenhao Zhao, Feng Lin, Xiaobing Cao, Xian Cui, Jinquan Wei
It is of great importance to investigate the crystallization of organometallic perovskite from solution for enhancing performance of perovskite solar cells. Here, this study develops a facile method for in situ observation of crystallization and growth of the methylammonium lead iodide (MAPbI3 ) perovskite from microdroplets ejected by an alternating viscous and inertial force jetting method. It is found that there are two crystallization modes when MAPbI3 grows from the CH3 NH3 I (MAI)/PbI2 /N,N-dimethylformamide (DMF) solution: needle precursors and granular perovskites...
May 17, 2017: Small
Emilia Olsson, Xavier Aparicio-Anglès, Nora H de Leeuw
The substitutional doping of Ca(2+), Sr(2+), and Ba(2+) on the Sm-site in the cubic perovskite SmCoO3 is reported to improve both electronic and ionic conductivities for applications as solid oxide fuel cell (SOFC) cathodes. Hence, in this study we have used density functional theory (DFT) calculations to investigate dopant configurations at two different dopant concentrations: 25 and 50%. To preserve the electroneutrality of the system, we have studied two different charge compensation mechanisms: the creation of oxygen vacancies, and electronic holes...
May 17, 2017: Physical Chemistry Chemical Physics: PCCP
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