Docente
USP
Fernando Pereira Sabino
Publicações
2026
Vieira, Pedro Roberto Lopes; Rivera, Daniel D.; Farigliano, Lucas Martin; Sabino, Fernando P.; Dalpian, Gustavo Martini
Alloy engineering of Magnetic phases in two-dimensional Chromium Trihalides Journal Article
Em: arXiv e-prints, pp. arXiv:2607.10030, 2026.
@article{2026arXiv260710030L,
title = {Alloy engineering of Magnetic phases in two-dimensional Chromium Trihalides},
author = {Pedro Roberto Lopes Vieira and Daniel D. Rivera and Lucas Martin Farigliano and Fernando P. Sabino and Gustavo Martini Dalpian},
doi = {10.48550/arXiv.2607.10030},
year = {2026},
date = {2026-07-01},
urldate = {2026-07-01},
journal = {arXiv e-prints},
pages = {arXiv:2607.10030},
abstract = {Two-dimensional magnetic materials offer unique opportunities for exploring low-dimensional spin phenomena and next-generation spintronic devices. Chromium trihalides CrX3 (X = Cl, Br, I) belong to an important family of these materials, where alloying opens pathways for tailoring their electronic, magnetic, optical properties, and thermodynamic stability. In this work, we present a density functional theory study of CrX3 compounds and their ternary alloys. Our results show that for the pure compounds, the ground state is ferromagnetic (FM), with the antiferromagnetic-zigzag (AFM-Z) and paramagnetic (PM) phases being close in energy. For these pure systems, the band gap variation among different magnetic phases does not exceed 0.16 eV, and the average magnetic moments on Cr atoms increase from Cl to Br to I. For the alloys, the FM state remains the lowest-energy configuration, but the energy difference towards the AFM-Z phase decreases for compounds with lower iodine concentration. The calculated band gaps reveal a pronounced bowing along the compositional edge connecting CrCl3 and CrI3. The Curie temperatures show a smooth variation across compositions, consistent with the nearly linear behavior of the magnetic exchange parameters. Based on the calculated mixing enthalpy and configurational entropy, the approximate Gibbs free energy indicates that alloy formation becomes thermodynamically favorable at finite temperatures, which is important to overcome the intrinsic experimental instability of these compounds.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Two-dimensional magnetic materials offer unique opportunities for exploring low-dimensional spin phenomena and next-generation spintronic devices. Chromium trihalides CrX3 (X = Cl, Br, I) belong to an important family of these materials, where alloying opens pathways for tailoring their electronic, magnetic, optical properties, and thermodynamic stability. In this work, we present a density functional theory study of CrX3 compounds and their ternary alloys. Our results show that for the pure compounds, the ground state is ferromagnetic (FM), with the antiferromagnetic-zigzag (AFM-Z) and paramagnetic (PM) phases being close in energy. For these pure systems, the band gap variation among different magnetic phases does not exceed 0.16 eV, and the average magnetic moments on Cr atoms increase from Cl to Br to I. For the alloys, the FM state remains the lowest-energy configuration, but the energy difference towards the AFM-Z phase decreases for compounds with lower iodine concentration. The calculated band gaps reveal a pronounced bowing along the compositional edge connecting CrCl3 and CrI3. The Curie temperatures show a smooth variation across compositions, consistent with the nearly linear behavior of the magnetic exchange parameters. Based on the calculated mixing enthalpy and configurational entropy, the approximate Gibbs free energy indicates that alloy formation becomes thermodynamically favorable at finite temperatures, which is important to overcome the intrinsic experimental instability of these compounds.
Lemes, Maykon Alves; Sabino, Fernando Pereira; Dalpian, Gustavo Martini; Souza, Jose Antonio
Lanthanide-induced magnetic functionality and conductivity enhancement in MAPbI3 via water-assisted recrystallization Journal Article
Em: Appl. Phys. A, vol. 132, não 7, 2026, ISSN: 1432-0630.
@article{Lemes2026,
title = {Lanthanide-induced magnetic functionality and conductivity enhancement in MAPbI3 via water-assisted recrystallization},
author = {Maykon Alves Lemes and Fernando Pereira Sabino and Gustavo Martini Dalpian and Jose Antonio Souza},
doi = {10.1007/s00339-026-09812-8},
issn = {1432-0630},
year = {2026},
date = {2026-06-22},
journal = {Appl. Phys. A},
volume = {132},
number = {7},
publisher = {Springer Science and Business Media LLC},
abstract = {<jats:title>Abstract</jats:title>
<jats:p>
Lanthanide incorporation into hybrid halide perovskites offers a promising route to introduce magnetic functionality while tuning charge-transport behavior. Here, we report the incorporation of paramagnetic rare-earth ions (Gd
<jats:sup>3</jats:sup>
⁺, Tb
<jats:sup>3</jats:sup>
⁺, and Dy
<jats:sup>3</jats:sup>
⁺) into MAPbI₃ through a water-assisted dissociation-recrystallization strategy that enables trapping of 4f ions within the restored 3D perovskite-derived lattice. Powder X-ray diffraction confirms preservation of the tetragonal I4/mcm structure, while ICP-MS verifies the presence of lanthanides in the final materials. Magnetic susceptibility measurements reveal robust paramagnetic behavior governed by the 4f electronic configuration, with effective magnetic moments of μ
<jats:sub>eff</jats:sub> = 9.12 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Tb and 20.22 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Dy. Electrical measurements show a pronounced reduction in dark resistance, decreasing from approximately 7.7 × 10⁷ Ω for pristine MAPbI₃ to about 1.0 × 10
<jats:sup>4</jats:sup>
Ω for the most conductive Ln-doped sample, indicating a substantial enhancement of charge transport upon lanthanide incorporation. Under illumination, all samples exhibit reversible photoconductive behavior. Density functional theory calculations, performed using simplified substitutional models, provide exploratory electronic-structure scenarios: Gd-related unoccupied 4f states may lie within or near the conduction band, whereas Tb and Dy can introduce localized f-derived states within the bandgap, which may contribute to carrier trapping and modified recombination dynamics. Optical absorption measurements indicate subtle bandgap modulation without significant changes in the radiative band-to-band emission. These results demonstrate that water-assisted recrystallization is a viable strategy to introduce magnetic functionality into MAPbI₃ while substantially modifying its electrical response, and they identify lanthanide-doped MAPbI₃ as a promising multifunctional platform for future optoelectronic and spintronic studies.
</jats:p>
<jats:p>
<jats:bold>Graphical abstract</jats:bold>
</jats:p>
<jats:p>A significant conductivity enhancement is observed when rare-earth ions are incorporated into an iodine-based 3D perovskite matrix. The results also reveal the emergence of magnetic functionality associated with the inclusion of 4f paramagnetic ions. Although the photoluminescence spectra of the doped samples remain similar to that of pristine MAPbI₃, clear changes in optical absorption and electrical transport are observed.</jats:p>},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
<jats:title>Abstract</jats:title>
<jats:p>
Lanthanide incorporation into hybrid halide perovskites offers a promising route to introduce magnetic functionality while tuning charge-transport behavior. Here, we report the incorporation of paramagnetic rare-earth ions (Gd
<jats:sup>3</jats:sup>
⁺, Tb
<jats:sup>3</jats:sup>
⁺, and Dy
<jats:sup>3</jats:sup>
⁺) into MAPbI₃ through a water-assisted dissociation-recrystallization strategy that enables trapping of 4f ions within the restored 3D perovskite-derived lattice. Powder X-ray diffraction confirms preservation of the tetragonal I4/mcm structure, while ICP-MS verifies the presence of lanthanides in the final materials. Magnetic susceptibility measurements reveal robust paramagnetic behavior governed by the 4f electronic configuration, with effective magnetic moments of μ
<jats:sub>eff</jats:sub> = 9.12 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Tb and 20.22 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Dy. Electrical measurements show a pronounced reduction in dark resistance, decreasing from approximately 7.7 × 10⁷ Ω for pristine MAPbI₃ to about 1.0 × 10
<jats:sup>4</jats:sup>
Ω for the most conductive Ln-doped sample, indicating a substantial enhancement of charge transport upon lanthanide incorporation. Under illumination, all samples exhibit reversible photoconductive behavior. Density functional theory calculations, performed using simplified substitutional models, provide exploratory electronic-structure scenarios: Gd-related unoccupied 4f states may lie within or near the conduction band, whereas Tb and Dy can introduce localized f-derived states within the bandgap, which may contribute to carrier trapping and modified recombination dynamics. Optical absorption measurements indicate subtle bandgap modulation without significant changes in the radiative band-to-band emission. These results demonstrate that water-assisted recrystallization is a viable strategy to introduce magnetic functionality into MAPbI₃ while substantially modifying its electrical response, and they identify lanthanide-doped MAPbI₃ as a promising multifunctional platform for future optoelectronic and spintronic studies.
</jats:p>
<jats:p>
<jats:bold>Graphical abstract</jats:bold>
</jats:p>
<jats:p>A significant conductivity enhancement is observed when rare-earth ions are incorporated into an iodine-based 3D perovskite matrix. The results also reveal the emergence of magnetic functionality associated with the inclusion of 4f paramagnetic ions. Although the photoluminescence spectra of the doped samples remain similar to that of pristine MAPbI₃, clear changes in optical absorption and electrical transport are observed.</jats:p>
<jats:p>
Lanthanide incorporation into hybrid halide perovskites offers a promising route to introduce magnetic functionality while tuning charge-transport behavior. Here, we report the incorporation of paramagnetic rare-earth ions (Gd
<jats:sup>3</jats:sup>
⁺, Tb
<jats:sup>3</jats:sup>
⁺, and Dy
<jats:sup>3</jats:sup>
⁺) into MAPbI₃ through a water-assisted dissociation-recrystallization strategy that enables trapping of 4f ions within the restored 3D perovskite-derived lattice. Powder X-ray diffraction confirms preservation of the tetragonal I4/mcm structure, while ICP-MS verifies the presence of lanthanides in the final materials. Magnetic susceptibility measurements reveal robust paramagnetic behavior governed by the 4f electronic configuration, with effective magnetic moments of μ
<jats:sub>eff</jats:sub> = 9.12 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Tb and 20.22 μ
<jats:sub>B</jats:sub>
for MAPbI₃:Dy. Electrical measurements show a pronounced reduction in dark resistance, decreasing from approximately 7.7 × 10⁷ Ω for pristine MAPbI₃ to about 1.0 × 10
<jats:sup>4</jats:sup>
Ω for the most conductive Ln-doped sample, indicating a substantial enhancement of charge transport upon lanthanide incorporation. Under illumination, all samples exhibit reversible photoconductive behavior. Density functional theory calculations, performed using simplified substitutional models, provide exploratory electronic-structure scenarios: Gd-related unoccupied 4f states may lie within or near the conduction band, whereas Tb and Dy can introduce localized f-derived states within the bandgap, which may contribute to carrier trapping and modified recombination dynamics. Optical absorption measurements indicate subtle bandgap modulation without significant changes in the radiative band-to-band emission. These results demonstrate that water-assisted recrystallization is a viable strategy to introduce magnetic functionality into MAPbI₃ while substantially modifying its electrical response, and they identify lanthanide-doped MAPbI₃ as a promising multifunctional platform for future optoelectronic and spintronic studies.
</jats:p>
<jats:p>
<jats:bold>Graphical abstract</jats:bold>
</jats:p>
<jats:p>A significant conductivity enhancement is observed when rare-earth ions are incorporated into an iodine-based 3D perovskite matrix. The results also reveal the emergence of magnetic functionality associated with the inclusion of 4f paramagnetic ions. Although the photoluminescence spectra of the doped samples remain similar to that of pristine MAPbI₃, clear changes in optical absorption and electrical transport are observed.</jats:p>
2025
Rivera, D.; Sabino, Fernando P.; Raebiger, H.; Ruzsinszky, A.; Perdew, J. P.; Dalpian, G. M.
Exchange field induced symmetry breaking in quantum hexaborides Miscellaneous
2025.
@misc{rivera2025exchangefieldinducedsymmetry,
title = {Exchange field induced symmetry breaking in quantum hexaborides},
author = {D. Rivera and Fernando P. Sabino and H. Raebiger and A. Ruzsinszky and J. P. Perdew and G. M. Dalpian},
url = {https://arxiv.org/abs/2511.05738},
year = {2025},
date = {2025-11-07},
urldate = {2025-01-01},
abstract = {Symmetry breaking (SB) has proven to be a powerful approach for describing quantum materials: strong correlation, mass renormalization, and complex phase transitions are among the phenomena that SB can capture, even when coupled to a mean-field-like theory. Traditionally, corrective schemes were required to account for these effects; however, SB has emerged as an alternative that can also successfully describe the intricate physics of quantum materials. Here, we explore spin SB on EuB6 and SmB6 and how its relation to the exchange field can determine onsite properties, depending on the type of symmetry breaking. Using spin-polarized Density Functional Theory (DFT) calculations with the r2SCAN functional, we systematically compare four magnetic configurations, one totally symmetric - non-magnetic (NM) configuration - and three with different types of symmetry breaking: ferromagnetic (FM), antiferromagnetic (AFM) and a paramagnetic (PM) configuration - modeled through a Special Quasirandom Structure (SQS) method - to capture local symmetry-breaking effects. Our results show that the PM configuration produces distinct magnetic environments for the rare-earth atoms, leading to different exchange fields. These, in turn, induce symmetry breaking in the electronic and magnetic properties of Eu and Sm. Those results provide an alternative explanation for the experimental results on both materials, EuB6 and SmB6, where X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Near Edge Structure (XANES) measurements suggest the presence of multiple atomic environments, previously attributed to a mixed-valence configuration.},
keywords = {},
pubstate = {published},
tppubtype = {misc}
}
Symmetry breaking (SB) has proven to be a powerful approach for describing quantum materials: strong correlation, mass renormalization, and complex phase transitions are among the phenomena that SB can capture, even when coupled to a mean-field-like theory. Traditionally, corrective schemes were required to account for these effects; however, SB has emerged as an alternative that can also successfully describe the intricate physics of quantum materials. Here, we explore spin SB on EuB6 and SmB6 and how its relation to the exchange field can determine onsite properties, depending on the type of symmetry breaking. Using spin-polarized Density Functional Theory (DFT) calculations with the r2SCAN functional, we systematically compare four magnetic configurations, one totally symmetric - non-magnetic (NM) configuration - and three with different types of symmetry breaking: ferromagnetic (FM), antiferromagnetic (AFM) and a paramagnetic (PM) configuration - modeled through a Special Quasirandom Structure (SQS) method - to capture local symmetry-breaking effects. Our results show that the PM configuration produces distinct magnetic environments for the rare-earth atoms, leading to different exchange fields. These, in turn, induce symmetry breaking in the electronic and magnetic properties of Eu and Sm. Those results provide an alternative explanation for the experimental results on both materials, EuB6 and SmB6, where X-ray Absorption Spectroscopy (XAS) and X-ray Absorption Near Edge Structure (XANES) measurements suggest the presence of multiple atomic environments, previously attributed to a mixed-valence configuration.
2024
Sabino, Fernando P.; Zhao, Xin Gang; Dalpian, Gustavo M.; Zunger, Alex
Impact of symmetry breaking and spin-orbit coupling on the band gap of halide perovskites Journal Article
Em: Phys. Rev. B, vol. 110, iss. 3, pp. 035160, 2024.
@article{PhysRevB.110.035160,
title = {Impact of symmetry breaking and spin-orbit coupling on the band gap of halide perovskites},
author = {Fernando P. Sabino and Xin Gang Zhao and Gustavo M. Dalpian and Alex Zunger},
url = {https://link.aps.org/doi/10.1103/PhysRevB.110.035160},
doi = {10.1103/PhysRevB.110.035160},
year = {2024},
date = {2024-07-30},
urldate = {2024-07-01},
journal = {Phys. Rev. B},
volume = {110},
issue = {3},
pages = {035160},
publisher = {American Physical Society},
abstract = {Halide perovskite (HP) materials have recently emerged as a class of semiconductors with immense promise for various optoelectronic applications, ranging from solar cells to light-emitting diodes. One of the unique attributes of HPs is their tunable band gaps with different factors governing their value. The first factor is related to relativistic corrections [“mass-Darwin,” connected to the 𝑛𝑠2 lone pairs, and spin-orbit coupling (SOC)] that induce an orbital shift or degeneracy splitting, resulting in a band-gap reduction. The second factor involves the structural configuration: in HPs the local symmetry of each Wyckoff position tends to be broken, inducing an opening of the band gap. Based on high-throughput density functional theory calculations, this paper systematically studies a possible self-cancelation on the band-gap correction for HPs when the polymorphous configuration—structural effects—and the SOC—electronic effects—are included. Our results indicate that the nature of interplay between SOC and symmetry breaking (SB) is that they are independent decoupling effects to describe the band-gap magnitude in halide perovskites. As a result of that, we observe a transitivity of the band-gap description; i.e., if we know the band gap of halide perovskites without SB and SOC, we can independently add the effects of band-gap reduction due to SOC and band-gap opening due to SB, regardless of the order in which these effects are considered.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Halide perovskite (HP) materials have recently emerged as a class of semiconductors with immense promise for various optoelectronic applications, ranging from solar cells to light-emitting diodes. One of the unique attributes of HPs is their tunable band gaps with different factors governing their value. The first factor is related to relativistic corrections [“mass-Darwin,” connected to the 𝑛𝑠2 lone pairs, and spin-orbit coupling (SOC)] that induce an orbital shift or degeneracy splitting, resulting in a band-gap reduction. The second factor involves the structural configuration: in HPs the local symmetry of each Wyckoff position tends to be broken, inducing an opening of the band gap. Based on high-throughput density functional theory calculations, this paper systematically studies a possible self-cancelation on the band-gap correction for HPs when the polymorphous configuration—structural effects—and the SOC—electronic effects—are included. Our results indicate that the nature of interplay between SOC and symmetry breaking (SB) is that they are independent decoupling effects to describe the band-gap magnitude in halide perovskites. As a result of that, we observe a transitivity of the band-gap description; i.e., if we know the band gap of halide perovskites without SB and SOC, we can independently add the effects of band-gap reduction due to SOC and band-gap opening due to SB, regardless of the order in which these effects are considered.
2023
Sabino, Fernando P.; Dalpian, Gustavo M.; Zunger, Alex
Light-Induced Frenkel Defect Pair Formation Can Lead to Phase-Segregation of Otherwise Miscible Halide Perovskite Alloys Journal Article
Em: Advanced Energy Materials, vol. n/a, não n/a, pp. 2301539, 2023.
@article{https://doi.org/10.1002/aenm.202301539,
title = {Light-Induced Frenkel Defect Pair Formation Can Lead to Phase-Segregation of Otherwise Miscible Halide Perovskite Alloys},
author = {Fernando P. Sabino and Gustavo M. Dalpian and Alex Zunger},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.202301539},
doi = {https://doi.org/10.1002/aenm.202301539},
year = {2023},
date = {2023-10-11},
journal = {Advanced Energy Materials},
volume = {n/a},
number = {n/a},
pages = {2301539},
abstract = {Abstract Alloys of ABX3 halide perovskites (HP) exhibit unique phase behavior compared to traditional III-V and II-VI semiconductor alloys used in solar cells. While the latter typically have good mutual miscibility when their mixed components are size matched, and phase-segregate when size mismatched, HP alloys show good miscibility in the dark but can phase-segregate under light. Quantum mechanical calculations described herein reveal light-induced defect formation and migration hold the key. Specifically, the interaction between a halogen vacancy VX with halogen interstitial Xi forming together a Frenkel-pair defect emerges as the enabler for phase-segregation in HP alloys. At a threshold bromine composition in the Br-I alloys, the photogenerated holes in the valence band localize, creating thereby a doubly-charged iodine Frenkel-pair (VI + Ii)2+. Faster migration of iodine over bromine interstitial into the vacant iodine VI site leads to the formation of iodine-rich and iodine-depleted regions, establishing phase-segregation. Removal of the mobile defects–the agent of segregation–by dark thermal annealing, supplies the opposing force, leading to reversal of phase-segregation. This atomistic understanding can enable some control of the phase-segregation by selecting substituting elements on the B site–such as replacing some Pb by Sn–that are unable to form stable Frenkel defects.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Alloys of ABX3 halide perovskites (HP) exhibit unique phase behavior compared to traditional III-V and II-VI semiconductor alloys used in solar cells. While the latter typically have good mutual miscibility when their mixed components are size matched, and phase-segregate when size mismatched, HP alloys show good miscibility in the dark but can phase-segregate under light. Quantum mechanical calculations described herein reveal light-induced defect formation and migration hold the key. Specifically, the interaction between a halogen vacancy VX with halogen interstitial Xi forming together a Frenkel-pair defect emerges as the enabler for phase-segregation in HP alloys. At a threshold bromine composition in the Br-I alloys, the photogenerated holes in the valence band localize, creating thereby a doubly-charged iodine Frenkel-pair (VI + Ii)2+. Faster migration of iodine over bromine interstitial into the vacant iodine VI site leads to the formation of iodine-rich and iodine-depleted regions, establishing phase-segregation. Removal of the mobile defects–the agent of segregation–by dark thermal annealing, supplies the opposing force, leading to reversal of phase-segregation. This atomistic understanding can enable some control of the phase-segregation by selecting substituting elements on the B site–such as replacing some Pb by Sn–that are unable to form stable Frenkel defects.
Sabino, Fernando; Zhao, Xingang; Dalpian, Gustavo M.; Zunger, Alex
Correlation between band gap shifts due to symmetry breaking and spin-orbital coupling in halide perovskites Working paper
2023.
@workingpaper{2023APS..MARS41008S,
title = {Correlation between band gap shifts due to symmetry breaking and spin-orbital coupling in halide perovskites},
author = {Fernando Sabino and Xingang Zhao and Gustavo M. Dalpian and Alex Zunger},
url = {https://ui.adsabs.harvard.edu/abs/2023APS..MARS41008S/abstract},
year = {2023},
date = {2023-02-13},
urldate = {2023-01-01},
booktitle = {APS March Meeting Abstracts},
volume = {2023},
pages = {S41.008},
series = {APS Meeting Abstracts},
abstract = {The calculation of band gaps of Halide perovskites (HP) differs from analogous calculations of more conventional semiconductors in that two additional factors need to be considered: (i) creation of a structural polymorphous network (a distribution of octahedral titling for different octahedra in cubic structures) - which increase the band gaps and (ii) spin-orbital coupling (SOC) - generally reducing the band gaps for compounds with high Z atoms. This raises the question to what extent effects (i) and (ii) compensate each other or if they are correlated in some way. We addressed this question by a series of DFT band structure calculations on cubic ABX3 compounds where effects (i) and (ii) are both included; or both excluded, or including one at the time. For the most studied inorganic halide perovskites, the SOC - induced band gap reduction has a low correlation with the band gap increase due to polymorphous network formation. The accuracy of treating the gap shifts due to (i) and (ii) as independent corrections for nominal cubic Pm-3m structures will be presented and discussed.},
keywords = {},
pubstate = {published},
tppubtype = {workingpaper}
}
The calculation of band gaps of Halide perovskites (HP) differs from analogous calculations of more conventional semiconductors in that two additional factors need to be considered: (i) creation of a structural polymorphous network (a distribution of octahedral titling for different octahedra in cubic structures) - which increase the band gaps and (ii) spin-orbital coupling (SOC) - generally reducing the band gaps for compounds with high Z atoms. This raises the question to what extent effects (i) and (ii) compensate each other or if they are correlated in some way. We addressed this question by a series of DFT band structure calculations on cubic ABX3 compounds where effects (i) and (ii) are both included; or both excluded, or including one at the time. For the most studied inorganic halide perovskites, the SOC - induced band gap reduction has a low correlation with the band gap increase due to polymorphous network formation. The accuracy of treating the gap shifts due to (i) and (ii) as independent corrections for nominal cubic Pm-3m structures will be presented and discussed.
Bonadio, Ariany; Sabino, Fernando P.; Freitas, André L. M.; Felez, Marissol R.; Dalpian, Gustavo M.; Souza, Jose A.
Comparing the Cubic and Tetragonal Phases of MAPbI3 at Room Temperature Journal Article
Em: Inorganic Chemistry, vol. 62, não 19, pp. 7533-7544, 2023, (PMID: 37126785).
@article{doi:10.1021/acs.inorgchem.3c00874,
title = {Comparing the Cubic and Tetragonal Phases of MAPbI3 at Room Temperature},
author = {Ariany Bonadio and Fernando P. Sabino and André L. M. Freitas and Marissol R. Felez and Gustavo M. Dalpian and Jose A. Souza},
url = {https://doi.org/10.1021/acs.inorgchem.3c00874},
doi = {10.1021/acs.inorgchem.3c00874},
year = {2023},
date = {2023-01-01},
journal = {Inorganic Chemistry},
volume = {62},
number = {19},
pages = {7533-7544},
abstract = {Stability and maintenance of the crystal structure are the main drawbacks of the application of organic–inorganic perovskites in photovoltaic devices. The ΔT = 62 K robust shift of the structural phase transition observed here allows us to conduct a comprehensive study at room temperature of the tetragonal versus cubic phase on MAPbI3. The absence of the shift in the cubic transition for all-inorganic CsPbI3 samples confirms the importance of both orientation and dynamics of the organic cations. Our results provide a unique opportunity to evaluate the physical properties of both cubic and tetragonal phases of MAPbI3 at the same temperature, eliminating different phonon effects as possible causes for different properties. Besides higher electrical resistivity, the perovskite cubic phase presents a faster charge carrier lifetime than the tetragonal phase and partial PL quenching, pointing toward increased trap-assisted nonradiative recombination. The light absorption coefficient in the cubic phase is larger than the absorption in the tetragonal phase in the green region.},
note = {PMID: 37126785},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Stability and maintenance of the crystal structure are the main drawbacks of the application of organic–inorganic perovskites in photovoltaic devices. The ΔT = 62 K robust shift of the structural phase transition observed here allows us to conduct a comprehensive study at room temperature of the tetragonal versus cubic phase on MAPbI3. The absence of the shift in the cubic transition for all-inorganic CsPbI3 samples confirms the importance of both orientation and dynamics of the organic cations. Our results provide a unique opportunity to evaluate the physical properties of both cubic and tetragonal phases of MAPbI3 at the same temperature, eliminating different phonon effects as possible causes for different properties. Besides higher electrical resistivity, the perovskite cubic phase presents a faster charge carrier lifetime than the tetragonal phase and partial PL quenching, pointing toward increased trap-assisted nonradiative recombination. The light absorption coefficient in the cubic phase is larger than the absorption in the tetragonal phase in the green region.
Freitas, Andre Luiz Martins; Tofanello, Aryane; Sabino, Fernando Pereira; Felez, Marissol Rodrigues; Morais, Eliane Aparecida; Brochsztain, Sergio; Acuña, Jose Javier Sáez; Dalpian, Gustavo M.; Souza, Jose Antonio
Finite-Size Effects on Cs3Cu2I5 0D Electronic Nanostructures for Ultraviolet-Emitting Applications Journal Article
Em: ACS Applied Nano Materials, vol. 6, não 9, pp. 7196-7205, 2023.
@article{doi:10.1021/acsanm.3c00242,
title = {Finite-Size Effects on Cs3Cu2I5 0D Electronic Nanostructures for Ultraviolet-Emitting Applications},
author = {Andre Luiz Martins Freitas and Aryane Tofanello and Fernando Pereira Sabino and Marissol Rodrigues Felez and Eliane Aparecida Morais and Sergio Brochsztain and Jose Javier Sáez Acuña and Gustavo M. Dalpian and Jose Antonio Souza},
url = {https://doi.org/10.1021/acsanm.3c00242},
doi = {10.1021/acsanm.3c00242},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {ACS Applied Nano Materials},
volume = {6},
number = {9},
pages = {7196-7205},
abstract = {The potential to produce ultraviolet (UV) light-emitting devices has attracted significant interest in interdisciplinary fields, particularly in the use of 0D halide nanostructures due to their straightforward synthesis methods and exceptional efficiency in optoelectronics. Here, we present a systematic study involving nanostructure synthesis and significant changes in the electronic structure caused by finite-size effects. We have focused on the investigation of size effects on the UV-light emitting properties of all-inorganic Cs3Cu2I5 halide. We observe that bulk particles present a pronounced bright-blue emission at 440 nm with a high quantum yield of 80%. Very small quantum dots nanostructures (6–10 nm) reveal a significant shift of the photoluminescence peak down to ∼395 nm, close to the UV-A region, but with a quantum yield reduction of 10%. Surface engineering to obtain very small nanoparticles free from defects at the nanocrystal surface is crucial for maintaining a high quantum efficiency, allowing their use in UV-emitting devices.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The potential to produce ultraviolet (UV) light-emitting devices has attracted significant interest in interdisciplinary fields, particularly in the use of 0D halide nanostructures due to their straightforward synthesis methods and exceptional efficiency in optoelectronics. Here, we present a systematic study involving nanostructure synthesis and significant changes in the electronic structure caused by finite-size effects. We have focused on the investigation of size effects on the UV-light emitting properties of all-inorganic Cs3Cu2I5 halide. We observe that bulk particles present a pronounced bright-blue emission at 440 nm with a high quantum yield of 80%. Very small quantum dots nanostructures (6–10 nm) reveal a significant shift of the photoluminescence peak down to ∼395 nm, close to the UV-A region, but with a quantum yield reduction of 10%. Surface engineering to obtain very small nanoparticles free from defects at the nanocrystal surface is crucial for maintaining a high quantum efficiency, allowing their use in UV-emitting devices.