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Hendrik Utzat, Katherine E Shulenberger, Odin B Achorn, Michel Nasilowski, Timothy S Sinclair, Moungi G Bawendi
Cesium lead halide (CsPbX3, X = Cl, Br, I) perovskite nanocrystals (PNCs) have recently become a promising material for optoelectronic applications due to their high emission quantum yields and facile band gap tunability via both halide composition and size. The spectroscopy of single PNCs enhances our understanding of the effect of confinement on excitations in PNCs in the absence of obfuscating ensemble averaging and can also inform synthetic efforts. However, single PNC studies have been hampered by poor PNC photostability under confocal excitation, precluding interrogation of all but the most stable PNCs, leading to a lack of understanding of PNCs in the regime of high confinement...
October 17, 2017: Nano Letters
James Z Fan, Mengxia Liu, Oleksandr Voznyy, Bin Sun, Larissa Levina, Rafael Quintero-Bermudez, Min Liu, Olivier Ouellette, F Pelayo Garcia de Arquer, Sjoerd Hoogland, Edward H Sargent
Colloidal quantum dots are promising materials for tandem solar cells that complement to silicon and perovskites. These devices are fabricated from solution phase; however, existing methods for making infrared-bandgap CQD inks suffer agglomeration and fusion during solution exchange. Here we develop a ligand exchange that provides robust surface protection and thereby avoids aggregation. First, we exchanged long oleic acid ligands to a mixed system comprised of medium-chain ammonium and anionic chloride ligands; then, we re-shelled the surface using short halides and pseudohalide ligands that enabled transfer to a polar solvent...
October 17, 2017: ACS Applied Materials & Interfaces
Arun Kumar Sagotra, Claudio Cazorla
Finding solid-state electrolytes with high ionic conductivity near room temperature is an important prerequisite for developing all-solid-state electrochemical batteries. Here, we investigate the effects of point defects (vacancies) and biaxial stress on the superionic properties of fast-ion conductors (represented by the archetypal compounds CaF$_{2}$, Li-rich anti-perovskite Li$_{3}$OCl, and AgI) by using classical molecular dynamics and first-principles simulation methods. We find that the critical superionic temperature of all analysed families of fast-ion conductors can be reduced by several hundreds of degrees through the application of relatively small biaxial stresses ($|\sigma| \le 1$~GPa) on slightly defective samples ($c_{v} \sim 1$\%)...
October 16, 2017: ACS Applied Materials & Interfaces
Amrita Pal, Lai Kai Wen, Chia Yao Jun, Il Jeon, Yutaka Matsuo, Sergei Manzhos
We present a systematic comparative density functional theory-density functional tight binding study of multiple derivatives of C60 and C70 with different addends, in molecular as well as solid state. In particular, effects due to fullerene size, type and number of addends, and of crystallinity on band structure, charge transport, and optical properties are investigated. These are important, in particular, for rational selection of fullerene derivatives as acceptor and electron transport layers in organic as well as planar inverted perovskite solar cells...
October 16, 2017: Physical Chemistry Chemical Physics: PCCP
Linzhong Wu, Qixuan Zhong, Di Yang, Min Chen, Huicheng Hu, Qi Pan, Haiyu Liu, Muhan Cao, Yong Xu, Baoquan Sun, Qiao Zhang
Recently, all-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) nanocrystals (NCs) have drawn wide attention because of their excellent optoelectronic properties and potential applications. However, one of the most significant challenges of such NCs is their low stability against protonic solvent. In this work, we demonstrate that by incorporating a highly-branched capping ligand, trioctylphosphine oxide (TOPO), into the traditional oleic acid/oleylamine system, monodisperse CsPbX3 NCs with excellent optoelectronic properties can be achieved at elevated temperatures (up to 260 oC)...
October 16, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Marianna Gambino, Stefania Di Tommaso, Francesco Giannici, Alessandro Longo, Carlo Adamo, Frédéric Labat, Antonino Martorana
A combined experimental and theoretical study of Mg-doped LaGaO3 electrolyte was carried out, with the aim to unveil the interaction between oxygen vacancy (Vo) and perovskite B site cations. LaGaO3 (LG) and LaGa0.875Mg0.125O2.938 (LGM0125) samples were comprehensively characterized by X-ray absorption spectroscopy (XAS) and X-ray diffraction, in order to investigate short- and long-range structures of both undoped and Mg-doped materials. XAS analysis evidenced a preferential Ga-Vo interaction in LGM0125, confirmed by periodic hybrid density functional theory calculations, which were combined with a symmetry-independent classes (SICs) approach in order to (a) obtain a detailed picture of the different Mg and Vo configurations in the doped material and (b) characterize the structural features of the conducting sites...
October 14, 2017: Journal of Chemical Physics
Joel S Miller, Eric Campbell, Brandon Dick, Arnold Rheingold, Chuang Zhang, Xiaojie Liu, Zeev Vardeny
Photovoltaic Perovskites, most notably methylammonium lead triiodide, (NH3Me)PbI3, have recently attracted considerable attention, and based upon the 'Goldschmidt Tolerance Factor' hydrazinium should be able to occupy the same cation site as methylammonium. The reaction of N2H5+I- with PbI2 in DMF results in three types of yellow crystals; hexagonal, needle-like, and rod-like, whose structures were determined at 100 K. The hexagonal [P63/m: a = 10.8906(10) Å; b = 37.845(5) Å] crystals possess isolated face sharing octahedral [Pb2I9]5-, [PbI6]4-, and I- ions...
October 13, 2017: Chemistry: a European Journal
Hao Li, Leiming Tao, Feihong Huang, Qiang Sun, Xiaojuan Zhao, Junbo Han, Yan Shen, Mingkui Wang
Perovskite solar cells have been demonstrated as promising low-cost and highly-efficient next-generation solar cells. Enhancing VOC by minimization the interfacial recombination kinetics can further improve device performance. In this work, we for the first time reported on surface passivation of perovskite layers with chemical modified graphene oxides, which acts as efficient interlayer to reduce interfacial recombination and enhance hole extraction as well. Our modeling points out that the passivation effect mainly comes from the interaction between functional group (4-Fluorophenyl) and under-coordinated Pb ions...
October 13, 2017: ACS Applied Materials & Interfaces
Yani Chen, Yong Sun, Jiajun Peng, Junhui Tang, Kaibo Zheng, Ziqi Liang
Conventional 3D organic-inorganic halide perovskites have recently undergone unprecedented rapid development. Yet, their inherent instabilities over moisture, light, and heat remain a crucial challenge prior to the realization of commercialization. By contrast, the emerging 2D Ruddlesden-Popper-type perovskites have recently attracted increasing attention owing to their great environmental stability. However, the research of 2D perovskites is just in their infancy. In comparison to 3D analogues, they are natural quantum wells with a much larger exciton binding energy...
October 13, 2017: Advanced Materials
Yantao Chen, Yingli Chu, Xiaohan Wu, Wei Ou-Yang, Jia Huang
All-inorganic lead halide perovskite quantum dots (IHP QDs) have great potentials in photodetectors. However, the photoresponsivity is limited by the low charge transport efficiency of the IHP QD layers. High-performance phototransistors based on IHP QDs hybridized with organic semiconductors (OSCs) are developed. The smooth surface of IHP QD layers ensures ordered packing of the OSC molecules above them. The OSCs significantly improve the transportation of the photoexcited charges, and the gate effect of the transistor structure significantly enhances the photoresponsivity while simultaneously maintaining high Iphoto /Idark ratio...
October 13, 2017: Advanced Materials
Chuanxiao Xiao, Changlei Wang, Weijun Ke, Brian Gorman, Jichun Ye, Chun-Sheng Jiang, Yanfa Yan, Mowafak Al-Jassim
Electron-selective layers (ESLs) and hole-selective layers (HSLs) are critical in high-efficiency organic-inorganic lead halide perovskite (PS) solar cells for charge-carrier transport, separation, and collection. We developed a procedure to assess the quality of the ESL/PS junction by measuring potential distribution on cross-section of SnO2-based perovskite solar cells using Kelvin probe force microscopy. Using the potential profiling, we compared three types of cells made of different ESLs but otherwise having identical device structure: 1) cells with PS deposited directly on bare fluorine-doped SnO2 (FTO)-coated glass; 2) cells with an intrinsic SnO2 thin layer on the top of FTO as an effective ESL; and 3) cells with the SnO2 ESL and adding a self-assembled monolayer (SAM) of fullerene...
October 13, 2017: ACS Applied Materials & Interfaces
Weihai Zhang, Juan Xiong, Li Jiang, Jianying Wang, Tao Mei, Xianbao Wang, Haoshuang Gu, Walid A Daoud, Jinhua Li
As electron transport layer (ETL) of perovskite solar cells, oxide semiconductor Zinc oxide (ZnO) has been attracted great attention due to its relatively high mobility, optical transparency, low temperature fabrication and good environment stability. However, the nature of ZnO will react with the patron on methylamine, which would deteriorate the performances of cells. Although many methods including high temperature annealing, doping and surface modification have been studied to improve the efficiency and stability of perovskite solar cells with ZnO ETL, devices remains relatively low efficiency and stability...
October 13, 2017: ACS Applied Materials & Interfaces
Xuanwen Liu, Junhua You, Renchao Wang, Zhiyuan Ni, Fei Han, Lei Jin, Zhiqi Ye, Zhao Fang, Rui Guo
Dy2Cu2O5 nanoparticles with perovskite structures were synthesized via a simple solution method (SSM) and a coordination compound method (CCM) using [DyCu(3,4-pdc)2(OAc)(H2O)2]•10.5H2O (pdc = 3,4-pyridinedicarboxylic acid) as precursor. The as-prepared samples were structurally characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS) and standard Brunauer-Emmett-Teller (BET) methods. Compared to the aggregated hexahedral particles prepared by SSM, the Dy2Cu2O5 of CCM showed hollow spherical morphology composed of nanoparticles with average diameters of 100-150 nm and a larger special surface area up to 36...
October 12, 2017: Scientific Reports
Samer Aphrham, Qing Pan, Sarah F Zaccarine, Kevin M Felter, Jos Thieme, Karin J H van den Nieuwenhuijzen, Johan E Ten Elshof, Annemarie Huijser
The effect of water addition during preparation of a CH3NH3PbI3 layer on the photodynamics is studied by femtosecond transient absorption. Both the regular perovskite and the aqueous analogue show charge thermalisation on a ca. 500 fs time scale. This process is however less pronounced in the latter layer. The spectral feature associated with hot charges does not fully decay on this time scale, but also shows a long-lived (sub-ns) component. As water molecules may interfere with the hydrogen bonding between the CH3NH3+ cations and the inorganic cage, this effect is possibly caused by immobilisation of cation motion, suggesting a key role of CH3NH3+ dipole reorientation in charge thermalisation...
October 12, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Junwei Xu, Wenxiao Huang, Peiyun Li, Drew R Onken, Chaochao Dun, Yang Guo, Kamil B Ucer, Chang Lu, Hongzhi Wang, Scott M Geyer, Richard T Williams, David L Carroll
Solution-grown films of CsPbBr3 nanocrystals imbedded in Cs4 PbBr6 are incorporated as the recombination layer in light-emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr3 and the nanoinclusion composite are measured and analyzed, indicating second-order kinetics in extended and mainly first-order kinetics in the confined CsPbBr3 , respectively. Analysis of absorption strength of this all-perovskite, all-inorganic imbedded nanocrystal composite relative to pure CsPbBr3 indicates enhanced oscillator strength consistent with earlier published attribution of the sub-nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr3 in melt-grown CsBr host crystals and CsPbBr3 evaporated films...
October 10, 2017: Advanced Materials
Yen-Hung Lin, Pichaya Pattanasattayavong, Thomas D Anthopoulos
Following the unprecedented rise in photovoltaic power conversion efficiencies during the past five years, metal-halide perovskites (MHPs) have emerged as a new and highly promising class of solar-energy materials. Their extraordinary electrical and optical properties combined with the abundance of the raw materials, the simplicity of synthetic routes, and processing versatility make MHPs ideal for cost-efficient, large-volume manufacturing of a plethora of optoelectronic devices that span far beyond photovoltaics...
October 12, 2017: Advanced Materials
Valerio Adinolfi, Wei Peng, Grant Walters, Osman M Bakr, Edward H Sargent
Organometal halide perovskites are under intense study for use in optoelectronics. Methylammonium and formamidinium lead iodide show impressive performance as photovoltaic materials; a premise that has spurred investigations into light-emitting devices and photodetectors. Herein, the optical and electrical material properties of organometal halide perovskites are reviewed. An overview is given on how the material composition and morphology are tied to these properties, and how these properties ultimately affect device performance...
October 12, 2017: Advanced Materials
Claudiu M Iaru, Jaco J Geuchies, Paul M Koenraad, Daniël Vanmaekelbergh, Andrei Yu Silov
We highlight the importance of carrier-phonon coupling in inorganic lead halide perovskite nanocrystals. The low-temperature photoluminescence (PL) spectrum of CsPbBr3 has been investigated under a nonresonant and a nonstandard, quasi-resonant excitation scheme, and phonon replicas of the main PL band have been identified as due to the Fröhlich interaction. The energy of longitudinal optical (LO) phonons has been determined from the separation of the zero phonon band and phonon replicas. We reason that the observed LO phonon coupling can only be related to an orthorhombically distorted crystal structure of the perovskite nanocrystals...
October 16, 2017: ACS Nano
Irene Grill, Meltem Fatma Aygüler, Thomas Bein, Pablo Docampo, Nicolai F Hartmann, Matthias Handloser, Achim Hartschuh
Understanding the charge transport characteristics and their limiting factors in organo-lead halide perovskites is of great importance for the development of competitive and economically advantageous photovoltaic systems derived from these materials. In the present work we examine the charge carrier mobilities in CH3NH3PbI3 (MAPI) thin films obtained from a one-step synthesis procedure and in planar n-i-p devices based on these films. By performing Time-of-Flight measurements, we find mobilities around 6 cm2/Vs for electrons and holes in MAPI thin films, while in working solar cells the respective mobility values are reduced by three orders of magnitude...
October 11, 2017: ACS Applied Materials & Interfaces
Hidekazu Ikeno, Teruyasu Mizoguchi
The electron energy loss near edge structures (ELNES) appearing in an electron energy loss spectrum obtained through transmission electron microscopy (TEM) have the potential to unravel atomic and electronic structures with sub-nano meter resolution. For this reason, TEM-ELNES has become one of the most powerful analytical methods in materials research. On the other hand, theoretical calculations are indispensable in interpreting the ELNES spectrum. Here, the basics and applications of one-particle, two-particle and multi-particle ELNES calculations are reviewed...
October 1, 2017: Microscopy
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