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YoungMi Lee, Jinwoo Park, Byung Deok Yu, Suklyun Hong, Min-Cherl Jung, Masakazu Nakamura
To understand the instability of Sn-based perovskite, CH3 NH3 SnI3 , photoelectron spectroscopy with the synchrotron radiation and theoretical calculations such as density functional theory and ab-initio molecular dynamics were performed. From these experimental and theoretical works, we found the crucial changes of surface-chemical states, the broken chemical bondings in Sn-I, and the depletion of a CH3 -NH3 molecule in the surface region. The material instability origin of Sn-based perovskite can be explained by the chemical state instability in the surface...
April 18, 2018: Journal of Physical Chemistry Letters
Weiyin Gao, Chenxin Ran, Jun Xi, Bo Jiao, Wenwen Zhang, Mincai Wu, Xun Hou, Zhaoxin Wu
All inorganic double metal perovskite materials have recently drawn much attention due to their three dimensionality (3D) and non-toxic nature to replace lead based perovskite material. Among all those double perovskite materials, theoretical works have demonstrated that Cs2AgBiBr6 shows high stability and possesses suitable bandgap for solar cell application. However, the film-forming ability of Cs2AgBiBr6 is found to be the utmost challenge hindering its development in thin film solar cell device. In this work, high quality Cs2AgBiBr6 film with ultra-smooth morphology, micro-sized grains, and high crystallinity is realized via anti-solvent dropping technology and post-annealing process under high temperature...
April 17, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Shuai You, Hui Wang, Shiqing Bi, Jiyu Zhou, Liang Qin, Xiaohui Qiu, Zhiqiang Zhao, Yun Xu, Yuan Zhang, Xinghua Shi, Huiqiong Zhou, Zhiyong Tang
Traps in the photoactive layer or interface can critically influence photovoltaic device characteristics and stabilities. Here, traps passivation and retardation on device degradation for methylammonium lead trihalide (MAPbI3 ) perovskite solar cells enabled by a biopolymer heparin sodium (HS) interfacial layer is investigated. The incorporated HS boosts the power conversion efficiency from 17.2 to 20.1% with suppressed hysteresis and Shockley-Read-Hall recombination, which originates primarily from the passivation of traps near the interface between the perovskites and the TiO2 cathode...
April 18, 2018: Advanced Materials
Aurora Manzi, Yu Tong, Julius Feucht, En-Ping Yao, Lakshminarayana Polavarapu, Alexander S Urban, Jochen Feldmann
Multi-photon absorption and multiple exciton generation represent two separate strategies for enhancing the conversion efficiency of light into usable electric power. Targeting below-band-gap and above-band-gap energies, respectively, to date these processes have only been demonstrated independently. Here we report the combined interaction of both nonlinear processes in CsPbBr3 perovskite nanocrystals. We demonstrate nonlinear absorption over a wide range of below-band-gap excitation energies (0.5-0.8 Eg )...
April 17, 2018: Nature Communications
Jialong Duan, Yuanyuan Zhao, Benlin He, Qunwei Tang
Perovskite solar cells with cost-effectiveness, high power conversion efficiency, and improved stability are promising solutions to the energy crisis and environmental pollution. However, a wide-bandgap inorganic-semiconductor electron-transporting layer such as TiO2 can harvest ultraviolet light to photodegrade perovskite halides, and the high cost of a state-of-the-art hole-transporting layer is an economic burden for commercialization. Here, the building of a simplified cesium lead bromide (CsPbBr3 ) perovskite solar cell with fluorine-doped tin oxide (FTO)/CsPbBr3 /carbon architecture by a multistep solution-processed deposition technology is demonstrated, achieving an efficiency as high as 4...
April 17, 2018: Small
Chunqing Ma, Dong Shen, Tsz-Wai Ng, Ming-Fai Lo, Chun-Sing Lee
2D perovskites have emerged as one of the most promising photovoltaic materials owing to their excellent stability compared with their 3D counterparts. However, in typical 2D perovskites, the highly conductive inorganic layers are isolated by large organic cations leading to quantum confinement and thus inferior electrical conductivity across layers. To address this issue, the large organic cations are replaced with small propane-1,3-diammonium (PDA) cations to reduce distance between the inorganic perovskite layers...
April 17, 2018: Advanced Materials
Chia-Lung Tsai, Yi-Chen Lu, Sheng Hsiung Chang
Photocurrent extraction and electron injection in CH3NH3PbBr3 (MAPbBr3) perovskite-based optoelectronic devices are both significantly increased by improving the contact at the PCBM/MAPbBr3 interface with an extended solvent annealing (ESA) process. Photoluminescence quenching and X-ray diffraction experiments show that the ESA not only improves the contact at the PCBM/MAPbBr3 interface but also increases the crystallinity of the MAPbBr3 thin films. The optimized dual-functional PCBM-MAPbBr3 heterojunction based optoelectronic device has a high power conversion efficiency of 4...
April 17, 2018: Nanotechnology
Hyeonggeun Yu, Yuanhang Cheng, Menglin Li, Sai-Wing Tsang, Franky So
Direct integration of an infrared photodetector with an organic light-emitting diode (OLED) enables low cost, pixel-free infrared imaging. However, the operation voltage of the resulting infrared-to-visible up-conversion is large due to the series device architecture. Here, we report a low voltage near infrared (NIR)-to-visible up-conversion device using formamidinium lead iodide as a NIR absorber integrated with a phosphorescent OLED. Due to the efficient photocarrier injection from the hybrid perovskite layer to the OLED, we observed a sub-bandgap turn-on of the OLED under NIR illumination...
April 17, 2018: ACS Applied Materials & Interfaces
Dazhi Wang, Xiaojun Zhao, Yigao Lin, Junsheng Liang, Tongqun Ren, Zhenghao Liu, Jiangyu Li
Controlled patterning of nanostructures at desired positions is of great importance for high-performance M/NEMS devices. Here, we demonstrate a high-resolution, high-speed and cost-effective fabrication method, named coaxial focused electrohydrodynamic jet printing, to print functional nanostructures. A coaxial needle was designed and developed; a functional ink and high viscosity liquid are applied in the inner and outer needle, respectively. Under optimised conditions, a stable coaxial jet is formed; then, the electrical shearing force and electrical field induce viscous shearing force and internal pressure that are jointly applied on the inner functional ink, focusing the inner jet on the nanoscale...
April 17, 2018: Nanoscale
Bin Yang, Wenmei Ming, Mao-Hua Du, Jong K Keum, Alexander A Puretzky, Christopher M Rouleau, Jinsong Huang, David B Geohegan, Xiaoping Wang, Kai Xiao
A fundamental understanding of the interplay between the microscopic structure and macroscopic optoelectronic properties of organic-inorganic hybrid perovskite materials is essential to design new materials and improve device performance. However, how exactly the organic cations affect the structural phase transition and optoelectronic properties of the materials is not well understood. Here, real-time, in situ temperature-dependent neutron/X-ray diffraction and photoluminescence (PL) measurements reveal a transformation of the organic cation CH3 NH3 + from order to disorder with increasing temperature in CH3 NH3 PbBr3 perovskites...
April 16, 2018: Advanced Materials
Shuo Shi, Ling-Dong Sun, Ying-Xian Xue, Hao Dong, Ke Wu, Shi-Chen Guo, Botao Wu, Chun-Hua Yan
One-dimensional nano/micro-structured semiconductor and lanthanide materials are attractive for polarized light emission studies. Upconversion emission from single nanorod or anisotropic nanoparticle has also been discussed with a degree of polarization. However, microscale arrays of nanoparticles, especially well-aligned one-dimensional nanostructures as well as their upconversion polarization characters have not been investigated yet. Herein, we present a novel and facile paradigm for preparing highly-aligned arrays of lanthanide-doped KMnF3 (KMnF3:Ln) perovskite nanowires, which are good candidates for polarized upconversion emission studies...
April 13, 2018: Nano Letters
Zhaosheng Zhang, Wei-Hai Fang, Marina V Tokina, Run Long, Oleg V Prezhdo
No abstract text is available yet for this article.
April 13, 2018: Nano Letters
Quinten Adriaan Akkerman, Ahmed L Abdelhady, Liberato Manna
Over the past decade, lead halide perovskites (LHPs) have emerged as new promising materials in the fields of photovoltaics and light emission due to their facile syntheses and exciting optical properties. The enthusiasm generated by LHPs has inspired research in perovskite-related materials, including so-called 'zero-dimensional cesium lead halides' which will be the focus of this perspective. The structure of these materials is formed of disconnected lead halide octahedra that are stabilized by cesium ions...
April 13, 2018: Journal of Physical Chemistry Letters
Xiao-Ke Liu, Feng Gao
Recently, lead halide perovskite materials have attracted extensive interest, in particular, in the research field of solar cells. These materials are fascinating "soft" materials with semiconducting properties comparable to the best inorganic semiconductors like silicon and gallium arsenide. As one of the most promising perovskite family members, organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) offer rich chemical and structural flexibility for exploring excellent properties for optoelectronic devices, such as solar cells and light-emitting diodes (LEDs)...
April 13, 2018: Journal of Physical Chemistry Letters
Oleg V'yunov, Anatolii Belous, Sofiia Kobylianska, Leonid Kovalenko
The effect of starting reagents (PbI2:{CH3 NH3 I + CH3 NH3 Cl}) with different ratios in raw solutions on the microstructure of films of organic-inorganic perovskites CH3 NH3 PbI3-x Clx , as well as on the electrical properties, has been investigated. It was found that the crystallinity is increased sharply when the ratio of the starting reagents increases from 1:1 to 1:2 and is changed slightly with a further increase of ratio to 1:3. It is shown that when the ratio of starting reagents varies, the morphology of the films changes; at a ratio of 1:1, the films consist of needle-like particles, and when the ratio is increased, particles become roundish and then faceted...
April 12, 2018: Nanoscale Research Letters
Jianming Yang, Zhongcheng Yuan, Xianjie Liu, Slawomir Braun, Yanqing Li, Jian-Xin Tang, Feng Gao, Chun-Gang Duan, Mats Fahlman, Qinye Bao
Organometal halide perovskites are under rapid development and significant focus has been placed on their stability that currently presents a major obstacle for practical application. The energetics play a vital role in charge injection/extraction and transport properties in devices. Here, we in-situ investigate oxygen and water-induced energetic degradation in organometal halide perovskite films. Oxygen gas induces an upwards shift of the vacuum level of the perovskite films due to the formation of an oxygen-induced surface dipole and water vapor causes vacuum level significant downshift as well as the valence band binding energy referenced to Fermi level simultaneously increase so as to keep the ionization potential of the perovskite films unchanged...
April 13, 2018: ACS Applied Materials & Interfaces
Sofia Masi, Rosanna Mastria, Riccardo Scarfiello, Sonia Carallo, Concetta Nobile, Salvatore Gambino, Teresa Sibillano, Cinzia Giannini, Silvia Colella, Andrea Listorti, P Davide Cozzoli, Aurora Rizzo
Thanks to their high stability, good optoelectronic and extraordinary electrochromic properties, tungsten oxides are among the most valuable yet underexploited materials for energy conversion applications. Herein, colloidal one-dimensional carved nanocrystals of reduced tungsten trioxide (WO3-x) are successfully integrated, for the first time, as a hole-transporting layer (HTL) into CH3NH3PbI3 perovskite solar cells with a planar inverted device architecture. Importantly, the use of such preformed nanocrystals guarantees the facile solution-cast-only deposition of a homogeneous WO3-x thin film at room temperature, allowing achievement of the highest power conversion efficiency ever reported for perovskite solar cells incorporating raw and un-doped tungsten oxide based HTL...
April 12, 2018: Physical Chemistry Chemical Physics: PCCP
Go Yumoto, Hirokazu Tahara, Tokuhisa Kawawaki, Masaki Saruyama, Ryota Sato, Toshiharu Teranishi, Yoshihiko Kanemitsu
Combining the superior optical properties of their bulk counterparts with quantum confinement effects, lead halide perovskite nanocrystals are unique laser materials with low-threshold optical gain. In such nonlinear optical regime, multiple excitons are generated in the nanocrystals and strongly affect the optical gain through many-body interactions. Here, we investigate the exciton-exciton interactions in CsPbI3 nanocrystals by femtosecond transient absorption spectroscopy. From the analysis of the induced absorption signal observed immediately after the pump excitation, we estimated the binding energy for the hot biexcitons that are composed of an exciton at the band edge and a hot exciton generated by the pump pulse...
April 12, 2018: Journal of Physical Chemistry Letters
Shrikant A Mohitkar, Jürgen Nuss, Henning A Höppe, Claudia Felser, Martin Jansen
New Sr5Os3O13, as synthesized from binary constituents, exhibits several uncommon features. Its crystal structure is dominated by quasi-2D poly-oxoanions that correspond to unprecedented cutouts of the perovskite type of structure, where corner sharing (OsO6) octahedra aggregate to form terraced slabs. The Os5+/Os6+ mixed valence oxide displays a particular charge ordering scheme. One osmium atom (Os1) per formula unit is in the valence state of 5+ in the whole temperature range studied, while the two remaining sites (Os2A and Os2B) show full charge disorder at high temperatures, resulting in an average charge of 5...
April 12, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yun-Hyok Kye, Chol-Jun Yu, Un-Gi Jong, Yue Chen, Aron Walsh
The chemical stability of methylammonium lead iodide (MAPbI3 ) under humid conditions remains the primary challenge facing halide perovskite solar cells. We investigate defect processes in the water-intercalated iodide perovskite (MAPbI3 _H2 O) and monohydrated phase (MAPbI3 -H2 O) within a first-principles thermodynamic framework. We consider the formation energies of isolated and aggregated vacancy defects with different charge states under I-rich and I-poor conditions. It is found that a PbI2 (partial Schottky) vacancy complex can be formed readily, while the MAI vacancy complex is difficult to form in the hydrous compounds...
April 12, 2018: Journal of Physical Chemistry Letters
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