Publications by Type: Journal Articles

Wang S, Owusu KA, Mai L, Ke Y, Zhou Y, Hu P, Magdassi S, Long Y. Vanadium dioxide for energy conservation and energy storage applications: Synthesis and performance improvement. Appl. EnergyApplied Energy. 2018;211 :200 - 217.Abstract
Vanadium dioxide (VO2) is one of the most widely studied inorg. phase change material for energy storage and energy conservation applications. Monoclinic VO2 [VO2(M)] changes from semiconducting phase to metallic rutile phase at near room temp. and the resultant abrupt suppressed IR transmittance at high temp. makes it a potential candidate for thermochromic smart window application to cut the air-condition usage. Meanwhile proper elec. potential, stable structure and good interaction with lithium ions make metastable VO2 [VO2(B)] an attractive material for fabrication of electrodes for batteries and supercapacitors. However, some long-standing issues have plagued its usage. In thermochromic application, high transition temp. (τc), low luminous transmittance (Tlum) and undesirable solar modulation ability (ΔTsol) are the key problems, while in energy storage applications, short cycling lifetime and complex three-dimension microstructure are the major challenges. The common methods to produce VO2 polymorph are phys. vapor deposition (PVD), chem. vapor deposition (CVD), sol-gel synthesis, and hydrothermal method. CVD is an intensively studied method due to its ability to produce uniform films with precise stoichiometry, phase and morphol. control. This paper reviews the various CVD techniques to produce VO2 with controlled phases and the ternary diagram shows the relationship between film stoichiometry and various process conditions. The difference between the various CVD systems are commented and the process window to produce VO2 are tabulated. Some strategies to improve VO2's performance in both energy conservation and energy storage applications are discussed. [on SciFinder(R)]
Armon N, Greenberg E, Layani M, Rosen YS, Magdassi S, Shpaisman H. Continuous Nanoparticle Assembly by a Modulated Photo-Induced Microbubble for Fabrication of Micrometric Conductive Patterns. ACS Appl. Mater. InterfacesACS Applied Materials & Interfaces. 2017;9 (50) :44214 - 44221.Abstract
The laser-induced microbubble technique (LIMBT) has recently been developed for micro-patterning of various materials. In this method, a laser beam is focused on a dispersion of nanoparticles leading to the formation of a microbubble due to laser heating. Convection currents around the microbubble carry nanoparticles so that they become pinned to the bubble/substrate interface. The major limitation of this technique is that for most materials, a noncontinuous deposition is formed. We show that continuous patterns can be formed by preventing the microbubble from being pinned to the deposited material. This is done by modulating the laser so that the construction and destruction of the microbubble are controlled. When the method is applied to a dispersion of Ag nanoparticles, continuous elec. conductive lines are formed. Furthermore, the line width is narrower than that achieved by the std. nonmodulated LIMBT. This approach can be applied to the direct-write fabrication of micron-size conductive patterns in electronic devices without the use of photolithog. [on SciFinder(R)]
Perrin L, Pajor-Swierzy A, Magdassi S, Kamyshny A, Ortega F, Rubio RG. Evaporation of nanosuspensions on substrates with different hydrophobicity. ACS Appl. Mater. InterfacesACS Applied Materials & Interfaces. 2017 :Ahead of Print.Abstract
Liq. drop evapn. on surfaces is present in many industrial and medical applications, e.g. printed electronics, spraying of pesticides, DNA mapping, etc. Despite this strong interest, a theor. description of the dynamic of the evapn. of complex liq. mixts. and nanosuspensions is still lacking. Indeed, one of the aspects that have not been included in the current theor. descriptions is the competition between the kinetics of evapn. and the adsorption of surfactants and/or particles at the liq./vapor and liq./solid interfaces. Materials formed by an elec. isolating solid on which a patterned conducting layer formed by the deposits left after drop evapn. have been considered as very promising for building elec. circuits on flexible plastic substrates. In this work an exhaustive study of the evapn. of nanosuspensions of latex and hydrophobized silver nanoparticles on four substrates of different hydrophobicity. The advancing and receding contact angles as well as the time dependence of the vol. of the droplets have been measured over a broad range of particle concn. Also, mixts. of silver particles and a surfactant, commonly used in industrial printing have been examd. Furthermore, the adsorption kinetics at both the air/liq. and solid/liq. interfaces have been measured. Whereas the latex particles do not adsorb at the solid/liq. and only slightly reduce the surface tension, the silver particles strongly adsorb at both interfaces. The exptl. results of the evapn. process were compared with the predictions of the theory of Semenov et al. (Evapn. of Sessile Water Droplets: Universal Behavior in Presence of Contact Angle Hysteresis. Colloids Surf. Physicochem. Eng. Asp. 2011, 391 (1-3), 135-144) and showed surprisingly good agreement despite the theory was developed for pure liqs. The morphol. of the deposits left by the droplets after total evapn. was studied by scanning electronic microscopy, and the effect of the substrate, the particles nature and their concns. on these patterns are discussed. [on SciFinder(R)]
Rahmany S, Layani M, Magdassi S, Etgar L. Fully functional semi-transparent perovskite solar cell fabricated in ambient air. Sustainable Energy FuelsSustainable Energy & Fuels. 2017;1 (10) :2120 - 2127.Abstract
Org.-inorg. halide perovskite has excellent properties to function as light harvesters in solar cells due to the possibility to tune its optical properties and to use it as thin film absorber, at a few hundred-nanometer thicknesses. Herein, we demonstrate the fabrication of perovskite solar cells with controlled transparency, by the mesh assisted deposition process. Sequential fabrication of perovskite was performed in air, wherein a PbI2 grid was formed in the first step, and in the second step, the grid reacted selectively with methylammoniumiodide, resulting in a perovskite grid pattern. The best cells were obtained with a photoanode composed of mesoporous TiO2 with Al2O3 nanoparticles. The resulting semi-transparent perovskite solar cells, including a semi-transparent contact composed of MoO3/Au/MoO3 yielded a power conversion efficiency of 5.5% with an av. transparency of 26% and efficiency of 8% for cells fabricated with a gold contact. [on SciFinder(R)]
Yeshua T, Layani M, Dekhter R, Huebner U, Magdassi S, Lewis A. Micrometer to 15 nm Printing of Metallic Inks with Fountain Pen Nanolithography. SmallSmall. 2017 :Ahead of Print.Abstract
The field of printed electronics is continually trying to reduce the dimensions of the elec. components. Here, a method of printing metallic lines with widths as small as 15 nm and up to a few micrometers using fountain pen nanolithog. (FPN) is shown. The FPN technique is based on a bent nanopipette with at. force feedback that acts similar to a nanopen. The geometry of the nanopen allows for rapid placement accuracy of the printing tip, on any desired location, with the highest of optical sub-micrometer resoln. Using this nanopen, investigations of various inks are undertaken together with instrumental and script-tool development that allows accurate printing of multiple layers. This has led to the printing of conductive lines using inks composed of silver nanoparticles and salt solns. of silver and copper. In addn., it is shown that the method can be applied to substrates of various materials with minimal effect on the dimension of the line. The line widths are varied by using nanopens with different orifices or by tailoring the wetting properties of the ink on the substrate. Metallic interconnections of conducting lines are reported. [on SciFinder(R)]
Binyamin O, Keller G, Frid K, Larush L, Magdassi S, Gabizon R. Continues administration of Nano-PSO significantly increased survival of genetic CJD mice. Neurobiol. Dis.Neurobiology of Disease. 2017;108 :140 - 147.Abstract
We have shown previously that Nano-PSO, a nanodroplet formulation of pomegranate seed oil, delayed progression of neurodegeneration signs when administered for a designated period of time to TgMHu2ME199K mice, modeling for genetic prion disease. In the present work, we treated these mice with a self-emulsion formulation of Nano-PSO or a parallel Soybean oil formulation from their day of birth until a terminal disease stage. We found that long term Nano-PSO administration resulted in increased survival of TgMHu2ME199K lines by several months. Interestingly, initiation of treatment at day 1 had no clin. advantage over initiation at day 70, however cessation of treatment at 9 mo of age resulted in the rapid loss of the beneficial clin. effect. Pathol. studies revealed that treatment with Nano-PSO resulted in the redn. of GAG accumulation and lipid oxidn., indicating a strong neuroprotective effect. Contrarily, the clin. effect of Nano-PSO did not correlate with redn. in the levels of disease related PrP, the main prion marker. We conclude that long term administration of Nano-PSO is safe and may be effective in the prevention/delay of onset of neurodegenerative conditions such as genetic CJD. [on SciFinder(R)]
Sachyani E, Layani M, Tibi G, Avidan T, Degani A, Magdassi S. Enhanced movement of CNT-based actuators by a three-Layered structure with controlled resistivity. Sens. Actuators, BSensors and Actuators, B: Chemical. 2017;252 :1071 - 1077.Abstract
Due to their unique movement and the lack of motoric parts, flexible actuators have recently been attracting considerable attention in regards to fabrication of soft robots. One of the most known flexible actuators are electro-thermal actuators (ETAs), based on Carbon Nanotubes (CNT). These are bi-layered actuators, triggered elec., and capable of preforming actuation because of the different coeff. of thermal expansions (CTEs) of the layers. The main disadvantage of these actuators is their limited movement ability, therefore, significant efforts are being invested in improving the actuation of CNT-based actuators. A typical CNT-based actuator is composed of a CNT layer on a polyimide substrate. In this study we show how the deflection of the CNT-based actuators was improved by decreasing the resistance of the CNT layer. We also present, for the first time, a novel tri-layer structured actuator that enables extremely large movements, with a record value deflection of 300°, using a simple, low-cost fabrication method without any orientation of the layers. This was achieved by adding a third layer of a photopolymeriazble polymer on top of the two typical bilayer CNT Kapton device. We further modeled the effect of various parameters of the third layer, such as the Young's modulus and the thickness, on the actuation, supporting the exptl. data. [on SciFinder(R)]
Saada G, Layani M, Chernevousky A, Magdassi S. Hydroprinting Conductive Patterns onto 3D Structures. Adv. Mater. Technol. (Weinheim, Ger.)Advanced Materials Technologies (Weinheim, Germany). 2017;2 (5) :n/a.Abstract
A novel and facile method for printing functional conductive patterns on 3D objects with unconventional angles using hydroprinting of silver nanoparticles (NPs) ink is developed. Silver NPs ink is inkjet printed on water sol. polyvinyl alc. films. Sintering at room temp. is achieved by exposing the printed pattern to hydrochloric acid fumes. Elec. circuits are hydroprinted at low temp. (50 °C) on various 3D-printed structures and materials. The conductive patterns are hydroprinted on hard 90° angle objects and are assembled without any presence of sacrificial layer, which allows layer-by-layer overlap hydroprinting. In addn., elec. Light Emmiting Diode (LED) circuits and heater are successfully hydroprinted. To show the applicability of the process we hydroprinted a fully functional Near Field Communication (NFC) antenna onto a curved object, which was successfully paired with a smartphone. Anal. of hydroprinted patterns shows that the resistivity is 17.1 times higher than silver bulk which is considered suitable in most application. [on SciFinder(R)]
Li M, Magdassi S, Gao Y, Long Y. Hydrothermal Synthesis of VO2 Polymorphs: Advantages, Challenges and Prospects for the Application of Energy Efficient Smart Windows. SmallSmall. 2017;13 (36) :n/a.Abstract
Vanadium dioxide (VO2) is a widely studied inorg. phase change material, which has a reversible phase transition from semiconducting monoclinic to metallic rutile phase at a crit. temp. of τc ≈ 68 °C. The abrupt decrease of IR transmittance in the metallic phase makes VO2 a potential candidate for thermochromic energy efficient windows to cut down building energy consumption. However, there are three long-standing issues that hindered its application in energy efficient windows: high τc, low luminous transmittance (Tlum), and undesirable solar modulation ability (ΔTsol). Many approaches, including nano-thermochromism, porous films, biomimetic surface reconstruction, gridded structures, antireflective overcoatings, etc, have been proposed to tackle these issues. The first approach-nano-thermochromism-which is to integrate VO2 nanoparticles in a transparent matrix, outperforms the rest; while the thermochromic performance is detd. by particle size, stoichiometry, and crystallinity. A hydrothermal method is the most common method to fabricate high-quality VO2 nanoparticles, and has its own advantages of large-scale synthesis and precise phase control of VO2. This Review focuses on hydrothermal synthesis, phys. properties of VO2 polymorphs, and their transformation to thermochromic VO2(M), and discusses the advantages, challenges, and prospects of VO2(M) in energy-efficient smart windows application. [on SciFinder(R)]
Ashok Pawar A, Halivni S, Waiskopf N, Ben-Shahar Y, Soreni-Harari M, Bergbreiter S, Banin U, Magdassi S. Rapid Three-Dimensional Printing in Water Using Semiconductor-Metal Hybrid Nanoparticles as Photoinitiators. Nano Lett.Nano Letters. 2017;17 (7) :4497 - 4501.Abstract
Additive manufg. processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymn., which is the most versatile technol. enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradn., these particles form radicals through a photocatalytic process. Light absorption by the semiconductor nanorod is followed by charge sepn. and electron transfer to the metal tip, enabling redox reactions to form radicals in aerobic conditions. In particular, we demonstrate their use in 3D printing in water, where they simultaneously form hydroxyl radicals for the polymn. and consume dissolved oxygen that is a known inhibitor. We also demonstrate their potential for two-photon polymn. due to their giant two-photon absorption cross section. [on SciFinder(R)]
Tan JMR, Scott M, Hao W, Baikie T, Nelson CT, Pedireddy S, Tao R, Ling X, Magdassi S, White T, et al. Revealing Cation Exchange Induced Phase Transformations in Multi-Elemental Chalcogenide Nanoparticles. Chem. Mater.Chemistry of Materials. 2017 :Ahead of Print.Abstract
To control the process of cation exchange (CE) in multi-elemental system, a detailed understanding of structural changes at microscopic level is imperative. However, the synthesis of multi-elemental system has so far relied on the CE phenomenon of binary system which does not necessarily extend to the higher order systems. Here, a direct exptl. evidence supported by theor. calcns. reveal a growth model of binary Cu-S to ternary Cu-Sn-S to quaternary Cu-Zn-Sn-S which shows that cations preferentially diffuse along specific lattice plane with the preservation of sulfuric anionic framework. In addn., we also discover that unlike the commonly accepted structure (P63mc), the metastable crystal structure of Cu-Zn-Sn-S phase possesses fixed Sn occupancy sites. By revealing the preferential nature of cations diffusion and growth mechanism, our work provides insight to control the stoichiometry and phase purity of novel multi-elemental materials. [on SciFinder(R)]
Mendelson-Mastey C, Larush L, Danino D, Magdassi S. Synthesis of magnesium chloride nanoparticles by the water/oil nanoemulsion evaporation. Colloids Surf., AColloids and Surfaces, A: Physicochemical and Engineering Aspects. 2017;529 :930 - 935.Abstract
Dispersion of inorg. (magnesium chloride) nanoparticles in oil (octyl palmitate) was obtained by modifying a method based on solvent evapn. from nanometric droplets of water-in-oil nanoemulsion, which is usually used for obtaining org. nanoparticles. The particles size depends on the initial size of the emulsion droplets, and can be controlled by surfactant concn. and sonication time. At optimal conditions, the obtained nanoparticles are characterized by an av. diam. of about 100 nm (dynamic light scattering and Cryo-TEM), by their amorphous structure when dispersed in oil, and according to thermal gravimetric anal., by not contain free water after the evapn. process. The developed method is applicable for the prepn. of various inorg. nanoparticles, and can be utilized for the formulation of new delivery systems based on inorg. nanoparticles of minerals/salts dispersed in oil. [on SciFinder(R)]
Zhan Y, Tan MRJ, Cheng X, Tan WMA, Cai G, Chen J, Kumar V, Magdassi S, Lee PS. Ti-Doped WO3 synthesized by a facile wet bath method for improved electrochromism. J. Mater. Chem. CJournal of Materials Chemistry C: Materials for Optical and Electronic Devices. 2017;5 (38) :9995 - 10000.Abstract
Electrochromic materials could modulate the optical transmittance reversibly by the application of elec. potential and the increase in the surface area for fast ionic diffusion is an efficient way to improve their electrochromism. In this work, WO3 based nanomaterials with a size as small as 5 nm were synthesized via a facile wet bath method that leads to Ti doping of WO3 based on the heterovalency of W(VI) and Ti(IV). Ti doping improved the WO3 electrochromism effectiveness in transmittance contrast and coloration efficiency due to the reduced crystallite size and therefore an increase in the surface area, the Ti doping also enhanced the cycling stability benefiting from the stable Ti-O bonding. However, the coloring/bleaching kinetics were deteriorated due to the reduced proton diffusion coeff. after the Ti ion substitution into the WO3 lattice. A high coloration efficiency of 106.6 cm2 C-1 and a good optical contrast of ∼67.6% can be obtained for the optimized Ti-doped WO3 at a wavelength of 633 nm. [on SciFinder(R)]
Magdassi S, Bar-David S, Lahat G, Klausner J, Nizri E, Friedman-Levi Y, Eyal S, Zigmond E, Varol C, Lahat G, et al. Intraoperative Localization of Rectal Tumors Using Liposomal Indocyanine Green. Surg InnovSurgical innovation. 2017;24 (2) :139 - 144.Abstract
BACKGROUND: Tumor localization may pose a significant challenge during minimally invasive rectal resection. Near-infrared (NIR) imaging can penetrate biological tissue and afford tumor localization from the external surface of the rectum. Our aim was to develop an NIR-based tool for rectal tumor imaging that can be administered intravenously. METHODS: We prepared indocyanine-green (ICG)-loaded liposomes by sonication. Liposomes were evaluated for their size and morphology. We then used an endoscopically induced rectal cancer in mice as a model for rectal cancer. After intravenous administration, tumors were evaluated for their fluorescence intensity. Tumor intensity was expressed in relation to the background signal, that is, tumor to background ratio (TBR). RESULTS: Liposomes in various sizes could be prepared by adjusting sonication time. We selected 100-nm-sized liposomes for further experiments. Transmission electron microscopy showed spherical particles and confirmed the size measurements. The liposomes could be lyophilized and then rehydrated again before use without compromising their structure or signal. Fluorescence intensity was kept for 24 hours after solubilization. Testing the optimal time course for rectal tumor imaging revealed that early time course (up to 3 hours) yielded nonspecific imaging, whereas after long time course (24 hours), a very weak signal remained in the tissue. The optimal time window for imaging was after 12 hours from injection, with TBR = 8.1 ± 3.6 ( P = .002). Free ICG could not achieve similar results. CONCLUSIONS: The liposomal ICG can be reproducibly prepared and kept in lyophilized form. Liposomal ICG could serve as a tool for intraoperative tumor localization.[on SciFinder (R)]
Farraj Y, Smooha A, Kamyshny A, Magdassi S. Plasma-Induced Decomposition of Copper Complex Ink for the Formation of Highly Conductive Copper Tracks on Heat-Sensitive Substrates. ACS Appl Mater InterfacesACS applied materials & interfaces. 2017;9 (10) :8766 - 8773.Abstract
The use of Cu-formate-2-amino-2-methyl-1-propanol ink and low-pressure plasma for the formation of highly conductive patterns on heat sensitive plastic substrates was studied. It was found that plasma results in decomposition of copper complex to form metallic copper without heating at high temperatures. Ink composition and plasma parameters (predrying conditions, plasma treatment duration, gas type, and flow rate) were optimized to obtain uniform conductive metallic films. The morphology and electrical characteristics of these films were evaluated. Exposing the printed copper metallo-organic decomposition (MOD) ink to 160 W plasma for 8 min yielded resistivity as low as 7.3 ± 0.2 μΩ cm, which corresponds to 23% bulk copper conductivity. These results demonstrate the applicability of MOD inks and plasma treatment to obtain highly conductive printed patterns on low-cost plastic substrates and 3D printed polymers.[on SciFinder (R)]
Pajor-Swierzy A, Farraj Y, Kamyshny A, Magdassi S. Effect of carboxylic acids on conductivity of metallic films formed by inks based on copper@silver core-shell particles. Colloids Surf., AColloids and Surfaces, A: Physicochemical and Engineering Aspects. 2017;522 :320 - 327.Abstract
Conductive copper inks have attracted much attention as low-cost replacement for the currently used silver inks for printed electronics. The copper inks should be stable to oxidn. at all stages of fabrication of conductive patterns: ink formulation and storage, printing, and post-printing treatment. In the present study, air-stable copper-silver core-shell (Cu@Ag) submicron particles were utilized in conductive ink formulations. To improve the cond. of the resulting Cu@Ag coatings, the effect of various carboxylic acids was evaluated. It was found that all acids led to decreased resistivity after sintering at elevated temps., while the lowest value was only 4 times higher than the bulk resistivity at 3 wt% of oleic. The mechanism governing the effect of carboxylic acids is discussed, in view of possible stabilizer exchange and oxide dissoln. [on SciFinder(R)]
Patel DK, Sakhaei AH, Layani M, Zhang B, Ge Q, Magdassi S. Highly Stretchable and UV Curable Elastomers for Digital Light Processing Based 3D Printing. Adv. Mater. (Weinheim, Ger.)Advanced Materials (Weinheim, Germany). 2017;29 (15) :n/a.Abstract
The authors report a family of highly stretchable and UV curable (SUV) elastomer systems that are suitable for UV radiation based 3D printing. They present a printing with a digital light processing (DLP) printer, but the same compns. are suitable for a variety of UV 3D printers, such as SLA, Polyjet, and dispensing, while adjusting the viscosity. The DLP printable SUV elastomer resin formulations were prepd. by mixing a monofunctional monomer consisting of epoxy aliph. acrylate (EAA), and a difunctional cross-linker consisting of aliph. urethane diacrylate (AUD) dild. with 33 wt% of isobornyl acrylate. [on SciFinder(R)]
Farraj Y, Bielmann M, Magdassi S. Inkjet printing and rapid ebeam sintering enable formation of highly conductive patterns in roll to roll process. RSC Adv.RSC Advances. 2017;7 (25) :15463 - 15467.Abstract
Electron beam sintering at ambient pressure is demonstrated for the first time, in formation of highly conductive silver patterns composed of silver nanoparticles. Silver nanoparticles were inkjet printed on a plastic substrate, followed by rapid ebeam irradn., without causing any damage to the substrate. It was found that exposing the printed silver patterns to a dose of 600 kGy yielded a resistivity as low as 4.5 μΩ cm, which is only 2.8 times higher than that of the bulk silver. The effect of various parameters related to electron energy and penetration depth on the sintering efficiency was evaluated. This finding reveals the applicability of ebeam technol. in printed electronics for large-scale, roll-to-roll, high throughput printing processes. [on SciFinder(R)]
Wang N, Goh QS, Lee PL, Magdassi S, Long Y. One-step hydrothermal synthesis of rare earth/W-codoped VO2 nanoparticles: Reduced phase transition temperature and improved thermochromic properties. J. Alloys Compd.Journal of Alloys and Compounds. 2017;711 :222 - 228.Abstract
As a reversible thermochromic material, V dioxide (VO2) is a promising candidate for smart window applications. The trade-off between the integrated visible transmission (Tlum) and the solar modulating ability (ΔTsol), as well as the high phase transition temp. (τc∼68°) are regarded as the main obstacle for practical applications of pure VO2 nanomaterials. The combination of both high τc reducing efficiency of W and improving Tlum/ΔTsol properties of RE (rare earth: Eu, Tb), herein lies the purpose of RE/W-codoping to enhance the thermochromic performance. The RE/W-codoped VO2 nanoparticles were synthesized under hydrothermal conditions, and exhibited grain size of <100 nm. The smart window which was fabricated by coating RE/W-codoped VO2 nanoparticles onto glass, exhibits a thermochromic performance with a combination Tlum = 40%, ΔTsol = 6.3%, τc = 40.8° or Tlum = 63%, ΔTsol = 3.6%, τc = 31.9°, indicating the largely reduced absorption compared with the single W doping. Under the RE/W-codoping conditions, the ionic radius of the RE3+ cations controlled the crystallinity of the VO2 particles and the electron/hole carrier counteraction as well as the competition between the strain and the hole carrier played a vital role in modulating the τc of the VO2 products. The findings should be meaningful for studying the codoping mechanisms for VO2 nanomaterials. [on SciFinder(R)]
Li W, Su Z, Tan JMR, Chiam SY, Seng HL, Magdassi S, Wong LH. Revealing the Role of Potassium Treatment in CZTSSe Thin Film Solar Cells. Chem. Mater.Chemistry of Materials. 2017 :Ahead of Print.Abstract
Potassium (K) post-treatment on CIGSSe has been shown to yield the highest efficiency reported to date. However, very little is known on the effect of K doping in CZTSSe and the mechanism behind the efficiency improvement. Here we reveal the mechanism by which K enhances the charge sepn. in CZTSSe. We show that K accumulates at the CdS/CZTSSe, passivating the recombination at the front interface and improving carrier collection. K is also found to accumulate at the CZTSSe/Mo interface and facilitates the diffusion of Cd into the absorber which affects the morphol. and grain growth of CZTSSe. As revealed by the C-V, external quantum efficiency, and color J-V test, K doping significantly increases the carrier d., improves carrier collection, and passivates the front interface and grain boundaries, leading to the enhancement of Voc and Jsc. The av. power conversion efficiency has been promoted from 5% to above 7%, and the best 7.78% efficiency has been achieved for the 1.5 mol % K-doped CZTSSe device. This work offers some new insights into the K doping effects on CZTSSe via soln.-based approach and demonstrates the potential of facile control of K doping for further improvement of CZTSSe thin film solar cells. [on SciFinder(R)]