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Xin-Gang Zhao, Dongwen Yang, Yuanhui Sun, Tianshu Li, Lijun Zhang, Liping Yu, Alex Zunger
The long-term chemical instability and the presence of toxic Pb in otherwise stellar solar absorber APbX3 made of organic molecules on the A site and halogens for X have hindered their large-scale commercialization. Previously explored ways to achieve Pb-free halide perovskites involved replacing Pb(2+) with other similar M(2+) cations in ns(2) electron configuration, e.g., Sn(2+) or by Bi(3+) (plus Ag(+)), but unfortunately this showed either poor stability (M = Sn) or weakly absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps stability and good optoelectronic properties might be contraindicated...
April 21, 2017: Journal of the American Chemical Society
Chunqing Ma, Dong Shen, Jian Qing, Hrisheekesh Thachoth Chandran, Ming-Fai Lo, Chun-Sing Lee
Degradation mechanisms of methylammonium lead halide perovskite solar cells (PSCs) have drawn much attention recently. Herein, the bulk and surface degradation processes of the perovskite were differentiated for the first time by employing combinational studies using electrochemical impedance spectroscopy (EIS), capacitance frequency (CF), and X-ray diffraction (XRD) studies with particular attention on the roles of small polar molecules (MA(+) and H2O). CF study shows that short-circuit current density of the PSCs is increased by H2O at the beginning of the degradation process coupled with an increased surface capacitance...
April 21, 2017: ACS Applied Materials & Interfaces
Yingguo Yang, Shanglei Feng, Meng Li, Weidong Xu, Guangzhi Yin, Zhaokui Wang, Baoquan Sun, Xingyu Gao
Using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as hole conductor, a series of inverted planar CH3NH3PbI3-xClx perovskite solar cells (PSCs) were fabricated based on perovskite annealed by an improved time-temperature dependent (TTD) procedure in a flowing nitrogen atmosphere for different time. Only after an optimum annealing time, an optimized power conversion efficiency of 14.36% could be achieved. To understand their performance dependence on annealing time, an in situ real-time synchrotron-based grazing incidence X-ray diffraction (GIXRD) was used to monitor a step-by-step gradual structure transformation from distinct mainly organic-inorganic hybrid materials into highly ordered CH3NH3PbI3 crystal during annealing...
April 21, 2017: Scientific Reports
Ziang Xie, Shuren Sun, Yu Yan, Lili Zhang, Ruixiang Hou, Fuyang Tian, Guogang Qin
Very recently, the NH2CH=NH2PbI3 (FAPbI3) perovskite material has attracted much attention in fabricating solar cells (SCs). For a photovoltaic material, its refractive index and extinction coefficient, n(λ) and k(λ), as functions of λ, are important to study its optical properties and to estimate the power conversion efficiency potential for the SCs made of it. As far as we know, so far there is no reporting of n(λ) and k(λ) for the FAPbI3 material. In this article, with spectroscopic ellipsometry (SE) measurements, the n(λ) and k(λ), as well as Eg = 1...
April 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yintao Liu, Renxu Jia, Yucheng Wang, Ziyang Hu, Yuming Zhang, Tiqiang Pang, Yuejin Zhu, Suzhen Luan
The zero drift can severely deteriorate the stability of light-dark current ratio, detectivity and responsivity of the photodetectors. In this paper, the effects of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) doped perovskite based photodetector device on the inhibition of zero drift under dark state are discusses. Two kinds of photodetectors (Au/CH3NH3PbIxCl3-x/Au and Au/CH3NH3PbIxCl3-x:PCBM/Au) are prepared, and the materials and photodetector devices are measured by scanning electron microscope, X-ray diffraction, photoluminescence, ultra-violet absorption spectra, current-voltage and current-time...
April 21, 2017: ACS Applied Materials & Interfaces
Yangrunqian Wang, Jiawei Li, Qian Li, Weidong Zhu, Tao Yu, Xingyu Chen, Lu'an Yin, Yong Zhou, Xiaoyong Wang, Zhigang Zou
PbI2 heterogeneous-cap-induced crystallization with a face-to-face configuration is proposed to obtain efficient CH3NH3PbI3 perovskite films during thermal annealing. The films with large-size and dominative (110)-oriented grains can effectively boost the photovoltaic performance of the perovskite solar cells.
April 21, 2017: Chemical Communications: Chem Comm
Nobuya Sakai, Amir Abbas Haghighirad, Marina R Filip, Pabitra K Nayak, Simantini Nayak, Alexandra Ramadan, Zhiping Wang, Feliciano Giustino, Henry J Snaith
Lead halide perovskites are materials with excellent optoelectronic and photovoltaic properties. However, some hurdles remain prior to commercialization of these materials, such as chemical stability, phase stability, sensitivity to moisture, and potential issues due to the toxicity of lead. Here, we report a new type of lead-free perovskite related compound, Cs2PdBr6. This compound is solution processable, exhibits long-lived photoluminescence, and an optical band gap of 1.6 eV. Density functional theory calculations indicate that this compound has dispersive electronic bands, with electron and hole effective masses of 0...
April 20, 2017: Journal of the American Chemical Society
T A Nirmal Peiris, Ajay K Baranwal, Hiroyuki Kanda, Shota Fukumoto, Shusaku Kanaya, Ludmila Cojocaru, Takeru Bessho, Tsutomu Miyasaka, Hiroshi Segawa, Seigo Ito
In this article, we demonstrate for the first time a mesoscopic printable perovskite solar cell (PSC) using NiO as the hole transporting material and low-temperature processed carbon as the counter electrode. A single deposition method assisted by N2 blow drying was used for the deposition of MAPbI3 on a TiO2/ZrO2/NiO screen-printed electrode. As the final step a low-temperature processing (i.e. 75 °C) carbon counter layer was fabricated on MAPbI3 by a blade coating method. It is found that the capping layer thickness of MAPbI3 has a significant effect on the device efficiency, especially when NiO is introduced as a hole transporting material into the structure...
April 20, 2017: Nanoscale
Lei Zhang, Yoshitaka Matsushita, Kazunari Yamaura, Alexei A Belik
Cation and anion ordering plays an important role in the properties of materials, in particular, in the properties of perovskite materials. Here we report on unusual 5-fold cation/charge ordering in high-pressure-synthesized (at 6 GPa and ∼1670 K) RMn3O6 perovskites with R = Gd-Tm and Y. R(3+), Mn(2+), and Mn(3+) cations are ordered at the A site in two separate chains consisting of R(3+) and alternating Mn(2+) (in tetrahedral coordination) and Mn(3+) (in square-planar coordination), while Mn(3+) and mixed-valent Mn(3+)/Mn(4+) are ordered at the B site in layers...
April 20, 2017: Inorganic Chemistry
Leigh Weston, A Janotti, X Y Cui, C Stampfl, C G Van de Walle
Perovskite zirconates such as SrZrO3 exhibit improved proton solubility and conductivity when doped with trivalent cations substituting at the Zr site. In this work, we present a detailed study of Sc and Y dopants in SrZrO3 based on first-principles, hybrid density-functional calculations. When substituting at the Zr site (ScZr, YZr), both dopants give rise to a single, deep acceptor level, where the neutral impurity forms a localized hole polaron state. The ε(0/-) charge transition levels are 0.60 eV and 0...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
Salawu Omotayo Akande, Alexander Chroneos, Udo Schwingenschlögl
In search for materials for intermediate temperature solid oxide fuel cells, (Pr/Gd)BaCo2O5.5 is investigated by first principles calculations. Antisite defects are considered as they may modify the electronic and O diffusion properties but are rarely studied in double perovskite oxides. Octahedrally coordinated Co atoms are shown to realize intermediate and high spin states for PrBaCo2O5.5 and GdBaCo2O5.5, respectively, while pyramidally coordinated Co atoms always have high spin. It turns out that O vacancy formation is significantly easier in PrBaCo2O5...
April 20, 2017: Physical Chemistry Chemical Physics: PCCP
Cheng-Min Ji, Zhihua Sun, Aurang Zeb, Sijie Liu, Jing Zhang, Maochun Hong, Junhua Luo
Perovskite hybrids (e.g. CH3NH3PbI3) are holding great promise in photovoltaics and optoelectronics, due to their remarkable semiconducting property and potential ferroelectricity. However, up to date it still lacks conclusive evidence for the bulk ferroelectricity of CH3NH3PbI3. In this context, it is highly desirable to assemble concrete perovskite ferroelectric hybrids with the semiconducting feature. Here we report, for the first time, a class of lead-free perovskite halides, (N-methylpyrrolidinium)3Sb2Cl9-9xBr9x (x = 0-1), showing large ferroelectric polarization (5...
April 20, 2017: Journal of Physical Chemistry Letters
Jin-Wook Lee, Yao-Tsung Hsieh, Nicholas De Marco, Sang-Hoon Bae, Qifeng Han, Yang Yang
Perovskite solar cells have become one of the strongest candidates for the next-generation solar energy technologies. A myriad of beneficial optoelectronic properties of the perovskite materials have enabled superb power conversion efficiencies (PCE) exceeding 22% for a single junction device. The high PCE achievable via low processing costs and relatively high variability in optical properties have opened new possibilities for perovskites in tandem solar cells. In this perspective, we will discuss current research trends in fabricating tandem perovskite-based solar cells in combination with a variety of mature photovoltaic devices such as organic, silicon, and Cu(In,Ga)(S,Se)2 (CIGS) solar cells...
April 19, 2017: Journal of Physical Chemistry Letters
Donghoon Shin, Han-Ill Yoo
The recent proposal of possible oxygen-thermomigration as a plausible mechanism for unipolar resistive switching of oxide memristors is now widely employed in modelling or simulating their memristive function on the grounds of the conventional picture that the mobile component O is always thermophobic, with its reduced heat-of-transport being equal to its migrational enthalpy (qO* = ΔHm > 0). At 1000 °C, we measured the thermomigration of mobile-component O in a prototype memristive perovskite, CaTi0.90Sc0...
April 19, 2017: Physical Chemistry Chemical Physics: PCCP
Po-Han Chang, Shang-Yi Liu, Yu-Bing Lan, Yi-Chen Tsai, Xue-Qian You, Chia-Shuo Li, Kuo-You Huang, Ang-Sheng Chou, Tsung-Chin Cheng, Juen-Kai Wang, Chih-I Wu
In this work, graphene-methylammonium lead iodide (MAPbI3) perovskite hybrid phototransistors fabricated by sequential vapor deposition are demonstrated. Ultrahigh responsivity of 1.73 × 10(7) A W(-1) and detectivity of 2 × 10(15) Jones are achieved, with extremely high effective quantum efficiencies of about 10(8)% in the visible range (450-700 nm). This excellent performance is attributed to the ultra-flat perovskite films grown by vapor deposition on the graphene sheets. The hybrid structure of graphene covered with uniform perovskite has high exciton separation ability under light exposure, and thus efficiently generates photocurrents...
April 19, 2017: Scientific Reports
Feng Xu, Taiyang Zhang, Ge Li, Yixin Zhao
The chloride doped CH3NH3PbI3-xClx perovskite had attracted great attention due to obvious performance enhancement with using of Cl additive and the controversial arguments on Cl function and mechanism behind it. Herein, we fabricated a series of CH3NH3PbI3-xClx perovskites with various Cl content via a gas/solid reaction between CH3NH2 gas with HPbI3-xClx (x=0-1). It is found that once the Cl content x>0.1, there is CH3NH3PbCl3 formed coexisted with CH3NH3PbI3-xClx(x=0.05-01). The small amount of Cl doping in CH3NH3PbI3-xClx(x=0...
April 19, 2017: ChemSusChem
Yingzhuang Ma, Parth Vashishtha, Kai Chen, Elijah Peach, David Ohayon, Justin Hodgkiss, Jonathan Halpert
It is commonly believed that excess PbI2 has beneficial effects for perovskite solar cells due to the modification of charge transport behavior at interfaces, by surface passivation and by blocking electron-hole recombination. Here, we introduce a dynamically dispensed spin coating technique in a two-step deposition to form a perovskite layer with controllable quantities of crystalline PbI2. Using this technique, the concentration of CH3NH3I solution is kept constant at the reaction interface, ensuring smooth growth of films...
April 19, 2017: ChemSusChem
Zewen Xiao, Ke-Zhao Du, Weiwei Meng, Jianbo Wang, David B Mitzi, Yanfa Yan
Recently, there has been substantial interest in developing double-B-cation halide perovskites, which hold the potential to overcome the toxicity and instability issues inherent within emerging lead halide-based solar absorber materials. Among all double perovskites investigated, In(I)-based Cs2InBiCl6 and Cs2InSbCl6 have been proposed as promising thin-film photovoltaic absorber candidates, with computational examination predicting suitable materials properties, including direct bandgap and small effective masses for both electrons and holes...
April 18, 2017: Journal of the American Chemical Society
Gill Sang Han, Hyun Woo Shim, Seongha Lee, Matthew Duff, Jung-Kun Lee
An electron transport layer (ETL) which selectively collects photogenerated electrons is an important constituent of halide perovskite (PSCs). While TiO2 film is widely used as an ETL of PSCs, the processing of TiO2 film with high electron mobility requires high temperature annealing and TiO2 dissociates the perovskite layer through a photocatalytic reaction. In the present study, we report an effective surface modification method of a room-temperature processed ZnO nanoparticle (NPs) layer as an alternative to TiO2 ETL...
April 17, 2017: ChemSusChem
Yu Zhong, Thomas J Sisto, Boyuan Zhang, Kiyoshi Miyata, X-Y Zhu, Michael L Steigerwald, Fay Ng, Colin Nuckolls
This Communication describes a new molecular design that yields ultranarrowband organic photodetectors. The design is based on a series of helically twisted molecular ribbons as the optoelectronic material. We fabricate charge collection narrowing photodetectors based on four different helical ribbons that differ in the wavelength of their response. The photodetectors made from these materials have narrow spectral response with full-width at half maxima of <20 nm. The devices reported here are superior by approximately a factor of 5 to those from traditional organic materials due to the narrowness of their response...
April 18, 2017: Journal of the American Chemical Society
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