The roles of mixed monovalent cations in CsFAPbI3 perovskites in terms of the optoelectronic prop... more The roles of mixed monovalent cations in CsFAPbI3 perovskites in terms of the optoelectronic properties and excited-state charge polarization are reported.
2 Incorporating Monovalent Cations 3 Mojtaba Abdi-Jalebi,*,† Meysam Pazoki,‡,§ Bertrand Philippe,... more 2 Incorporating Monovalent Cations 3 Mojtaba Abdi-Jalebi,*,† Meysam Pazoki,‡,§ Bertrand Philippe, M. Ibrahim Dar, Mejd Alsari,† 4 Aditya Sadhanala,† Giorgio Divitini, Roghayeh Imani, Samuele Lilliu, Jolla Kullgren, 5 Hak̊an Rensmo, Michael Graẗzel, and Richard H. Friend† 6 †Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United 7 Kingdom 8 ‡Department of Engineering Sciences, Solid State Physics, Uppsala University, Box 534, SE 751 21 Uppsala, Sweden 9 Department of Chemistry, Ångström Laboratory, Uppsala University, Box 538, SE 75121 Uppsala, Sweden 10 Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, Box 516, SE 75120 Uppsala, 11 Sweden 12 Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fed́eŕale de 13 Lausanne, Lausanne CH-1015, Switzerland 14 Department of Materials Science and Metallurgy, University of Cambridge, ...
The perovskite layer is the photoactive material within the hybrid perovskite solar cell (HPSC) d... more The perovskite layer is the photoactive material within the hybrid perovskite solar cell (HPSC) device by which the incoming photon energies are absorbed and transformed into charge carriers, and after the charge separation, the corresponding charge carriers are transported via the selective contacts for the photovoltaic operation. Optical fingerprints of these physical processes i.e. the spectral response during light absorption, charge separation, transport, recombination as well as other important phenomena such as Stark effects, electron-phonon interactions, ionic movement and Frenkel defect annihilation can be studied within the scope of time resolved photo-induced optical spectroscopy. The time scales of the main fundamental processes within perovskite solar cells directly affect the device performance, and can differ significantly from conventional solar cell technology devices. The processes varies from femtosecond to several seconds and many are strongly dependent on the ch...
Methylammonium lead iodide (MAPbI3) presents numerous characteristics which make it more complex ... more Methylammonium lead iodide (MAPbI3) presents numerous characteristics which make it more complex than conventional semi-conductors. In this chapter, we present a survey of the valuable insights provided by first principles calculations into the atomic scale properties of the material. We cover the roles of different types of bonding and their influence on the structure and phase stability; dynamical effects, with an emphasis on the significant anharmonicity present due both to the soft nature of the material and rotations of the MA cation; the wide ranging influence of spin–orbit coupling on the band structure, as well as electron–phonon coupling and its influence on charge carrier dynamics; and finally, the nature of point defects, and their electronic structure and mobility.
Raw data files pertaining to the materials characterization, DFT calculations and solar cell meas... more Raw data files pertaining to the materials characterization, DFT calculations and solar cell measurements.
The lead-free lanthanide iodide perovskite materials explored herein, show potentials for impleme... more The lead-free lanthanide iodide perovskite materials explored herein, show potentials for implementation as light absorber or charge transfer layer in perovskite solar cell devices.
Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials f... more Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in compositio ...
Abstract Technologies and catalysts for converting carbon dioxide (CO2) to immobile products are ... more Abstract Technologies and catalysts for converting carbon dioxide (CO2) to immobile products are of high interest to minimize greenhouse effects. Copper(I) is a promising catalytic active state of copper but hampered by the inherent instability in comparison to copper(II) or copper(0). Here, we report a stabilization of the catalytic active state of copper(I) by the formation of a mixed metal oxide CuInO2 nanoparticle during the CO2 electroreduction. Our result shows the incorporation of nanoporous Sn:In2O3 interlayer to Cu2O pre-catalyst system lead to the formation of CuInO2 nanoparticles with remarkably higher activity for CO2 electroreduction at lower overpotential in comparison to the conventional Cu nanoparticles derived from sole Cu2O. Operando Raman spectroelectrochemistry is employed to in-situ monitor the process of nanoparticles formation during the electrocatalytic process. The experimental data are collaborated with DFT calculations to provide insight into the electro-formation of the type of Cu-based mixed metal oxide catalyst during the CO2 electroreduction, where a formation mechanism via copper ion diffusion across the substrate is suggested.
Lead replacements with mono-, di-, and trivalent metals are reviewed and discussed with respect t... more Lead replacements with mono-, di-, and trivalent metals are reviewed and discussed with respect to their resulting optoelectronic properties.
We report significant improvements in the optoelectronic properties of lead halide perovskites wi... more We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+ and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron x-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice, as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films although the perovskite bandgap remains the same, indicating a shift in the Fermi level position towards the middle of the bandgap. Such a shift infers that incorporation of these monova...
Abstract Ion migration has recently been suggested to play critical roles in the operation of lea... more Abstract Ion migration has recently been suggested to play critical roles in the operation of lead halide perovskite solar cells. However, so far there has been no systematic investigation of how the monovalent cation affects the vacancy formation, ion migration and the associated hysteresis effect. Here, we present density functional theory calculations on all possible ion migration barriers in the perovskite materials with different cations i.e. CH3NH3PbI3, CH(NH2)2PbI3 and CsPbI3 in the tetragonal phase and investigate vacancy monovalent-cation interactions within the framework of the possible ion migrations. The most relevant ion movement (iodide) is investigated in greater detail and corresponding local structural changes, the relationships with the local ionic dielectric response, Stark effect and current-voltage hysteresis are discussed. We observe a correlation between the energy barrier for iodine migration and the magnitude of the dipole of the monovalent cation. From the data, we suggest a vacancy-dipole interaction mechanism by which the larger dipole of the monovalent cation can respond to and screen the local electric fields more effectively. The stronger response of the high dipolar monovalent cation to the vacancy electrostatic potential in turn leads to a lower local structural changes within the neighbouring octahedra. The presented data reveal a detailed picture of the ion movement, vacancy dipole interactions and the consequent local structural changes, which contain fundamental information about the photo-physics, and dielectric response of the material.
Organometallic halide perovskites (OMHPs) have recently emerged as a promising class of materials... more Organometallic halide perovskites (OMHPs) have recently emerged as a promising class of materials in photovoltaic technology. Here, we present an in-depth investigation of the physics in these systems by measuring the photoinduced absorption (PIA) in OMHPs as a function of materials composition, excitation wavelength, and modulation frequency. We report a photoinduced Stark effect that depends on the excitation wavelength and on the dipole strength of the monovalent cations in the A position of the ABX3 perovskite. The results presented are corroborated by density functional theory calculations and provide fundamental information about the photoinduced local electric field change under blue and red excitation as well as insights into the mechanism of light-induced ion displacement in OMHPs. For optimized perovskite solar cell devices beyond 19% efficiency, we show that excess thermalization energy of blue photons plays a role in overcoming the activation energy for ion diffusion.
The roles of mixed monovalent cations in CsFAPbI3 perovskites in terms of the optoelectronic prop... more The roles of mixed monovalent cations in CsFAPbI3 perovskites in terms of the optoelectronic properties and excited-state charge polarization are reported.
2 Incorporating Monovalent Cations 3 Mojtaba Abdi-Jalebi,*,† Meysam Pazoki,‡,§ Bertrand Philippe,... more 2 Incorporating Monovalent Cations 3 Mojtaba Abdi-Jalebi,*,† Meysam Pazoki,‡,§ Bertrand Philippe, M. Ibrahim Dar, Mejd Alsari,† 4 Aditya Sadhanala,† Giorgio Divitini, Roghayeh Imani, Samuele Lilliu, Jolla Kullgren, 5 Hak̊an Rensmo, Michael Graẗzel, and Richard H. Friend† 6 †Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United 7 Kingdom 8 ‡Department of Engineering Sciences, Solid State Physics, Uppsala University, Box 534, SE 751 21 Uppsala, Sweden 9 Department of Chemistry, Ångström Laboratory, Uppsala University, Box 538, SE 75121 Uppsala, Sweden 10 Molecular and Condensed Matter Physics, Department of Physics and Astronomy, Uppsala University, Box 516, SE 75120 Uppsala, 11 Sweden 12 Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fed́eŕale de 13 Lausanne, Lausanne CH-1015, Switzerland 14 Department of Materials Science and Metallurgy, University of Cambridge, ...
The perovskite layer is the photoactive material within the hybrid perovskite solar cell (HPSC) d... more The perovskite layer is the photoactive material within the hybrid perovskite solar cell (HPSC) device by which the incoming photon energies are absorbed and transformed into charge carriers, and after the charge separation, the corresponding charge carriers are transported via the selective contacts for the photovoltaic operation. Optical fingerprints of these physical processes i.e. the spectral response during light absorption, charge separation, transport, recombination as well as other important phenomena such as Stark effects, electron-phonon interactions, ionic movement and Frenkel defect annihilation can be studied within the scope of time resolved photo-induced optical spectroscopy. The time scales of the main fundamental processes within perovskite solar cells directly affect the device performance, and can differ significantly from conventional solar cell technology devices. The processes varies from femtosecond to several seconds and many are strongly dependent on the ch...
Methylammonium lead iodide (MAPbI3) presents numerous characteristics which make it more complex ... more Methylammonium lead iodide (MAPbI3) presents numerous characteristics which make it more complex than conventional semi-conductors. In this chapter, we present a survey of the valuable insights provided by first principles calculations into the atomic scale properties of the material. We cover the roles of different types of bonding and their influence on the structure and phase stability; dynamical effects, with an emphasis on the significant anharmonicity present due both to the soft nature of the material and rotations of the MA cation; the wide ranging influence of spin–orbit coupling on the band structure, as well as electron–phonon coupling and its influence on charge carrier dynamics; and finally, the nature of point defects, and their electronic structure and mobility.
Raw data files pertaining to the materials characterization, DFT calculations and solar cell meas... more Raw data files pertaining to the materials characterization, DFT calculations and solar cell measurements.
The lead-free lanthanide iodide perovskite materials explored herein, show potentials for impleme... more The lead-free lanthanide iodide perovskite materials explored herein, show potentials for implementation as light absorber or charge transfer layer in perovskite solar cell devices.
Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials f... more Layered two-dimensional (2D) hybrid organic-inorganic perovskites (HOP) are promising materials for light-harvesting applications because of their chemical stability, wide flexibility in compositio ...
Abstract Technologies and catalysts for converting carbon dioxide (CO2) to immobile products are ... more Abstract Technologies and catalysts for converting carbon dioxide (CO2) to immobile products are of high interest to minimize greenhouse effects. Copper(I) is a promising catalytic active state of copper but hampered by the inherent instability in comparison to copper(II) or copper(0). Here, we report a stabilization of the catalytic active state of copper(I) by the formation of a mixed metal oxide CuInO2 nanoparticle during the CO2 electroreduction. Our result shows the incorporation of nanoporous Sn:In2O3 interlayer to Cu2O pre-catalyst system lead to the formation of CuInO2 nanoparticles with remarkably higher activity for CO2 electroreduction at lower overpotential in comparison to the conventional Cu nanoparticles derived from sole Cu2O. Operando Raman spectroelectrochemistry is employed to in-situ monitor the process of nanoparticles formation during the electrocatalytic process. The experimental data are collaborated with DFT calculations to provide insight into the electro-formation of the type of Cu-based mixed metal oxide catalyst during the CO2 electroreduction, where a formation mechanism via copper ion diffusion across the substrate is suggested.
Lead replacements with mono-, di-, and trivalent metals are reviewed and discussed with respect t... more Lead replacements with mono-, di-, and trivalent metals are reviewed and discussed with respect to their resulting optoelectronic properties.
We report significant improvements in the optoelectronic properties of lead halide perovskites wi... more We report significant improvements in the optoelectronic properties of lead halide perovskites with the addition of monovalent ions with ionic radii close to Pb2+. We investigate the chemical distribution and electronic structure of solution processed CH3NH3PbI3 perovskite structures containing Na+, Cu+ and Ag+, which are lower valence metal ions than Pb2+ but have similar ionic radii. Synchrotron x-ray diffraction reveals a pronounced shift in the main perovskite peaks for the monovalent cation-based films, suggesting incorporation of these cations into the perovskite lattice, as well as a preferential crystal growth in Ag+ containing perovskite structures. Furthermore, the synchrotron X-ray photoelectron measurements show a significant change in the valence band position for Cu- and Ag-doped films although the perovskite bandgap remains the same, indicating a shift in the Fermi level position towards the middle of the bandgap. Such a shift infers that incorporation of these monova...
Abstract Ion migration has recently been suggested to play critical roles in the operation of lea... more Abstract Ion migration has recently been suggested to play critical roles in the operation of lead halide perovskite solar cells. However, so far there has been no systematic investigation of how the monovalent cation affects the vacancy formation, ion migration and the associated hysteresis effect. Here, we present density functional theory calculations on all possible ion migration barriers in the perovskite materials with different cations i.e. CH3NH3PbI3, CH(NH2)2PbI3 and CsPbI3 in the tetragonal phase and investigate vacancy monovalent-cation interactions within the framework of the possible ion migrations. The most relevant ion movement (iodide) is investigated in greater detail and corresponding local structural changes, the relationships with the local ionic dielectric response, Stark effect and current-voltage hysteresis are discussed. We observe a correlation between the energy barrier for iodine migration and the magnitude of the dipole of the monovalent cation. From the data, we suggest a vacancy-dipole interaction mechanism by which the larger dipole of the monovalent cation can respond to and screen the local electric fields more effectively. The stronger response of the high dipolar monovalent cation to the vacancy electrostatic potential in turn leads to a lower local structural changes within the neighbouring octahedra. The presented data reveal a detailed picture of the ion movement, vacancy dipole interactions and the consequent local structural changes, which contain fundamental information about the photo-physics, and dielectric response of the material.
Organometallic halide perovskites (OMHPs) have recently emerged as a promising class of materials... more Organometallic halide perovskites (OMHPs) have recently emerged as a promising class of materials in photovoltaic technology. Here, we present an in-depth investigation of the physics in these systems by measuring the photoinduced absorption (PIA) in OMHPs as a function of materials composition, excitation wavelength, and modulation frequency. We report a photoinduced Stark effect that depends on the excitation wavelength and on the dipole strength of the monovalent cations in the A position of the ABX3 perovskite. The results presented are corroborated by density functional theory calculations and provide fundamental information about the photoinduced local electric field change under blue and red excitation as well as insights into the mechanism of light-induced ion displacement in OMHPs. For optimized perovskite solar cell devices beyond 19% efficiency, we show that excess thermalization energy of blue photons plays a role in overcoming the activation energy for ion diffusion.
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