The overall synthesis of novel chiral nanosized metal-oxide nanofilms and surfaces, based on the ... more The overall synthesis of novel chiral nanosized metal-oxide nanofilms and surfaces, based on the chiral templating of cellulose with alumina using the atomic layer deposition process.
We synthesized Hg alloyed CdTe quantum dots (Cd1−xHgxTe) using hydrothermal route. N-acetyl-cyste... more We synthesized Hg alloyed CdTe quantum dots (Cd1−xHgxTe) using hydrothermal route. N-acetyl-cysteine is used as the capping agent for water dispersed Cd1−xHgxTe (x = 0, 0.05, 0.1 and 0.5) quantum dots. The diameter of the synthesized quantum dots is 3.8 ± 0.5 nm, as estimated from high resolution transmission electron micrographs. The mercury molar fraction modified band gap engineering is demonstrated with band gap changing from 2.5 eV for CdTe quantum dots to 1.25 eV for Cd0.5Hg0.5Te.
Recent progress in the field of hybrid organic-inorganic perovskites ABX3 for photovoltaics has g... more Recent progress in the field of hybrid organic-inorganic perovskites ABX3 for photovoltaics has given cells with certified efficiencies of 22.1 % solar to electric power, mainly based upon the hybrid inorganic-organic methylammonium lead iodide perovskite MAPbI3 (MA + = CH3NH + 3 ). Up to now, one of the biggest drawbacks is poor stability towards humidity and temperature. A substitution of the organic MA with inorganic Cs yields the extremely stable structure CsPbI3, which however forms a yellow δ-phase at room-temperature that is not photoactive. In this study we have systematically explored the mixed cation perovskite CsxMA1-xPbI3 as a material and demonstrate its benefits for photovoltaic applications. We exchanged the A-side cation by dipping MAPbI3 films into a CsI solution, thereby incrementally replacing the MA in a timeresolved dipping process and analysed the resulting thin-films with UV-Vis, XRD, EDAX, SEM and optical depth-analysis in a high-throughput fashion. Additiona...
The structural instability of organometal halide perovskites (OHP) is one of the major issues con... more The structural instability of organometal halide perovskites (OHP) is one of the major issues concerning commercialization of perovskite solar cells. Probing this intrinsic instability is one of the major milestones and challenging tasks toward enhancing the lifespan of the material. Here we have incorporated Cs ions into methylammonium lead iodide (MAPbI3) films and studied the thin film structural and optical properties. Incorporation of Cs into MAPbI3 leads to formation of both α-CsPbI3 and ∂-CsPbI3 phases, black and yellow, respectively, as indicated by the evolution of the optical band edge and X-ray diffraction (XRD) spectrum. At a concentration of 20% Cs ions, we observe the existence of a stable α-CsPbI3 phase. Incorporating 59% or more Cs ions yields the yellow phase of CsPbI3, due to alloying of Cs with the MAPbI3 matrix. The structural transformations observed in absorption spectra and XRD are confirmed by low-frequency Raman spectroscopy. The thermally induced structural fluctuations in pure MAPbI3 films are damped upon Cs incorporation, thus bringing long-range stabilized order to the perovskite structure and enabling for the first time observation of low-frequency Raman scattering at room temperature for OHPs. In addition to this, Cs incorporation rigidizes the perovskite film and sharpens all low-frequency vibrational peaks. This rigidizing effect can explain the importance of incorporating and alloying heavy elements into OHPs to bring both chemical stability and photostability
In this work, we describe the formation of a reduced bandgap CeNiO phase, which, to our knowledge... more In this work, we describe the formation of a reduced bandgap CeNiO phase, which, to our knowledge, has not been previously reported, and we show how it is utilized as an absorber layer in a photovoltaic cell. The CeNiO phase is prepared by a combinatorial materials science approach, where a library containing a continuous compositional spread of Ce NiO is formed by pulsed laser deposition (PLD); a method that has not been used in the past to form Ce-Ni-O materials. The library displays a reduced bandgap throughout, calculated to be 1.48-1.77 eV, compared to the starting materials, CeO and NiO, which each have a bandgap of ∼3.3 eV. The materials library is further analyzed by X-ray diffraction to determine a new crystalline phase. By searching and comparing to the Materials Project database, the reduced bandgap CeNiO phase is realized. The CeNiO reduced bandgap phase is implemented as the absorber layer in a solar cell and photovoltages up to 550 mV are achieved. The solar cells are ...
The overall synthesis of novel chiral nanosized metal-oxide nanofilms and surfaces, based on the ... more The overall synthesis of novel chiral nanosized metal-oxide nanofilms and surfaces, based on the chiral templating of cellulose with alumina using the atomic layer deposition process.
We synthesized Hg alloyed CdTe quantum dots (Cd1−xHgxTe) using hydrothermal route. N-acetyl-cyste... more We synthesized Hg alloyed CdTe quantum dots (Cd1−xHgxTe) using hydrothermal route. N-acetyl-cysteine is used as the capping agent for water dispersed Cd1−xHgxTe (x = 0, 0.05, 0.1 and 0.5) quantum dots. The diameter of the synthesized quantum dots is 3.8 ± 0.5 nm, as estimated from high resolution transmission electron micrographs. The mercury molar fraction modified band gap engineering is demonstrated with band gap changing from 2.5 eV for CdTe quantum dots to 1.25 eV for Cd0.5Hg0.5Te.
Recent progress in the field of hybrid organic-inorganic perovskites ABX3 for photovoltaics has g... more Recent progress in the field of hybrid organic-inorganic perovskites ABX3 for photovoltaics has given cells with certified efficiencies of 22.1 % solar to electric power, mainly based upon the hybrid inorganic-organic methylammonium lead iodide perovskite MAPbI3 (MA + = CH3NH + 3 ). Up to now, one of the biggest drawbacks is poor stability towards humidity and temperature. A substitution of the organic MA with inorganic Cs yields the extremely stable structure CsPbI3, which however forms a yellow δ-phase at room-temperature that is not photoactive. In this study we have systematically explored the mixed cation perovskite CsxMA1-xPbI3 as a material and demonstrate its benefits for photovoltaic applications. We exchanged the A-side cation by dipping MAPbI3 films into a CsI solution, thereby incrementally replacing the MA in a timeresolved dipping process and analysed the resulting thin-films with UV-Vis, XRD, EDAX, SEM and optical depth-analysis in a high-throughput fashion. Additiona...
The structural instability of organometal halide perovskites (OHP) is one of the major issues con... more The structural instability of organometal halide perovskites (OHP) is one of the major issues concerning commercialization of perovskite solar cells. Probing this intrinsic instability is one of the major milestones and challenging tasks toward enhancing the lifespan of the material. Here we have incorporated Cs ions into methylammonium lead iodide (MAPbI3) films and studied the thin film structural and optical properties. Incorporation of Cs into MAPbI3 leads to formation of both α-CsPbI3 and ∂-CsPbI3 phases, black and yellow, respectively, as indicated by the evolution of the optical band edge and X-ray diffraction (XRD) spectrum. At a concentration of 20% Cs ions, we observe the existence of a stable α-CsPbI3 phase. Incorporating 59% or more Cs ions yields the yellow phase of CsPbI3, due to alloying of Cs with the MAPbI3 matrix. The structural transformations observed in absorption spectra and XRD are confirmed by low-frequency Raman spectroscopy. The thermally induced structural fluctuations in pure MAPbI3 films are damped upon Cs incorporation, thus bringing long-range stabilized order to the perovskite structure and enabling for the first time observation of low-frequency Raman scattering at room temperature for OHPs. In addition to this, Cs incorporation rigidizes the perovskite film and sharpens all low-frequency vibrational peaks. This rigidizing effect can explain the importance of incorporating and alloying heavy elements into OHPs to bring both chemical stability and photostability
In this work, we describe the formation of a reduced bandgap CeNiO phase, which, to our knowledge... more In this work, we describe the formation of a reduced bandgap CeNiO phase, which, to our knowledge, has not been previously reported, and we show how it is utilized as an absorber layer in a photovoltaic cell. The CeNiO phase is prepared by a combinatorial materials science approach, where a library containing a continuous compositional spread of Ce NiO is formed by pulsed laser deposition (PLD); a method that has not been used in the past to form Ce-Ni-O materials. The library displays a reduced bandgap throughout, calculated to be 1.48-1.77 eV, compared to the starting materials, CeO and NiO, which each have a bandgap of ∼3.3 eV. The materials library is further analyzed by X-ray diffraction to determine a new crystalline phase. By searching and comparing to the Materials Project database, the reduced bandgap CeNiO phase is realized. The CeNiO reduced bandgap phase is implemented as the absorber layer in a solar cell and photovoltages up to 550 mV are achieved. The solar cells are ...
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Papers by Shay Tirosh