Cova de Can Sadurní, la transformació d’un jaciment. L’episodi sepulcral del neolític postcardial

The present study deals with the structural characterization and classification of the novel compounds <b>1</b>–<b>8</b> into perovskite subclasses and proceeds in extracting the structure–band gap relationships between them. The compounds were obtained from the employment of small, 3–5-atom-wide organic ammonium ions seeking to discover new perovskite-like compounds. The compounds reported here adopt unique or rare structure types akin to the prototype structure perovskite. When trimethylammonium (TMA) was employed, we obtained TMASnI₃ (<b>1</b>), which is our reference compound for a “perovskitoid” structure of face-sharing octahedra. The compounds EASnI₃ (<b>2b</b>), GASnI₃ (<b>3a</b>), ACASnI₃ (<b>4</b>), and IMSnI₃ (<b>5</b>) obtained from the use of ethylammonium (EA), guanidinium (GA), acetamidinium (ACA), and imidazolium (IM) cations, respectively, represent the first entries of the so-called “hexagonal perovskite polytypes” in the hybrid halide perovskite library. The hexagonal perovskites define a new family of hybrid halide perovskites with a crystal structure that emerges from a blend of corner- and face-sharing octahedral connections in various proportions. The small organic cations can also stabilize a second structural type characterized by a crystal lattice with reduced dimensionality. These compounds include the two-dimensional (2D) perovskites GA₂SnI₄ (<b>3b</b>) and IPA₃Sn₂I₇ (<b>6b</b>) and the one-dimensional (1D) perovskite IPA₃SnI₅ (<b>6a</b>). The known 2D perovskite BA₂MASn₂I₇ (<b>7</b>) and the related all-inorganic 1D perovskite “RbSnF₂I” (<b>8</b>) have also been synthesized. All compounds have been identified as medium-to-wide-band-gap semiconductors in the range of <i>E</i>_g = 1.90–2.40 eV, with the band gap progressively decreasing with increased corner-sharing functionality and increased torsion angle in the octahedral connectivity

Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties

A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI₃, where A is the methylammonium (CH₃NH₃⁺) or formamidinium (HC­(NH₂)₂⁺) cation and M is Sn (<b>1</b> and <b>2</b>) or Pb (<b>3</b> and <b>4</b>) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of <b>1</b>–<b>4</b> classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that <b>1</b>–<b>4</b> behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25–1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700–1000 nm range (1.1–1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH₃NH₃Sn_1–<i>x</i>Pb_<i>x</i>I₃ (<b>5</b>). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as <i>p</i>- or <i>n</i>-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are <i>n</i>-type; <i>p</i>-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn⁴⁺ and thus behave as <i>p</i>-type semiconductors displaying metal-like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm²/(V s) and 300 cm²/(V s), respectively, as shown in the case of CH₃NH₃SnI₃ (<b>1</b>). We also compare the properties of the title hybrid materials with those of the “all-inorganic” CsSnI₃ and CsPbI₃ prepared using identical synthetic methods

Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties

A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI₃, where A is the methylammonium (CH₃NH₃⁺) or formamidinium (HC­(NH₂)₂⁺) cation and M is Sn (<b>1</b> and <b>2</b>) or Pb (<b>3</b> and <b>4</b>) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of <b>1</b>–<b>4</b> classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that <b>1</b>–<b>4</b> behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25–1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700–1000 nm range (1.1–1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH₃NH₃Sn_1–<i>x</i>Pb_<i>x</i>I₃ (<b>5</b>). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as <i>p</i>- or <i>n</i>-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are <i>n</i>-type; <i>p</i>-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn⁴⁺ and thus behave as <i>p</i>-type semiconductors displaying metal-like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm²/(V s) and 300 cm²/(V s), respectively, as shown in the case of CH₃NH₃SnI₃ (<b>1</b>). We also compare the properties of the title hybrid materials with those of the “all-inorganic” CsSnI₃ and CsPbI₃ prepared using identical synthetic methods

Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties

A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI₃, where A is the methylammonium (CH₃NH₃⁺) or formamidinium (HC­(NH₂)₂⁺) cation and M is Sn (<b>1</b> and <b>2</b>) or Pb (<b>3</b> and <b>4</b>) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of <b>1</b>–<b>4</b> classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that <b>1</b>–<b>4</b> behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25–1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700–1000 nm range (1.1–1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH₃NH₃Sn_1–<i>x</i>Pb_<i>x</i>I₃ (<b>5</b>). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as <i>p</i>- or <i>n</i>-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are <i>n</i>-type; <i>p</i>-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn⁴⁺ and thus behave as <i>p</i>-type semiconductors displaying metal-like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm²/(V s) and 300 cm²/(V s), respectively, as shown in the case of CH₃NH₃SnI₃ (<b>1</b>). We also compare the properties of the title hybrid materials with those of the “all-inorganic” CsSnI₃ and CsPbI₃ prepared using identical synthetic methods

Semiconducting Tin and Lead Iodide Perovskites with Organic Cations: Phase Transitions, High Mobilities, and Near-Infrared Photoluminescent Properties

A broad organic–inorganic series of hybrid metal iodide perovskites with the general formulation AMI₃, where A is the methylammonium (CH₃NH₃⁺) or formamidinium (HC­(NH₂)₂⁺) cation and M is Sn (<b>1</b> and <b>2</b>) or Pb (<b>3</b> and <b>4</b>) are reported. The compounds have been prepared through a variety of synthetic approaches, and the nature of the resulting materials is discussed in terms of their thermal stability and optical and electronic properties. We find that the chemical and physical properties of these materials strongly depend on the preparation method. Single crystal X-ray diffraction analysis of <b>1</b>–<b>4</b> classifies the compounds in the perovskite structural family. Structural phase transitions were observed and investigated by temperature-dependent single crystal X-ray diffraction in the 100–400 K range. The charge transport properties of the materials are discussed in conjunction with diffuse reflectance studies in the mid-IR region that display characteristic absorption features. Temperature-dependent studies show a strong dependence of the resistivity as a function of the crystal structure. Optical absorption measurements indicate that <b>1</b>–<b>4</b> behave as direct-gap semiconductors with energy band gaps distributed in the range of 1.25–1.75 eV. The compounds exhibit an intense near-IR photoluminescence (PL) emission in the 700–1000 nm range (1.1–1.7 eV) at room temperature. We show that solid solutions between the Sn and Pb compounds are readily accessible throughout the composition range. The optical properties such as energy band gap, emission intensity, and wavelength can be readily controlled as we show for the isostructural series of solid solutions CH₃NH₃Sn_1–<i>x</i>Pb_<i>x</i>I₃ (<b>5</b>). The charge transport type in these materials was characterized by Seebeck coefficient and Hall-effect measurements. The compounds behave as <i>p</i>- or <i>n</i>-type semiconductors depending on the preparation method. The samples with the lowest carrier concentration are prepared from solution and are <i>n</i>-type; <i>p</i>-type samples can be obtained through solid state reactions exposed in air in a controllable manner. In the case of Sn compounds, there is a facile tendency toward oxidation which causes the materials to be doped with Sn⁴⁺ and thus behave as <i>p</i>-type semiconductors displaying metal-like conductivity. The compounds appear to possess very high estimated electron and hole mobilities that exceed 2000 cm²/(V s) and 300 cm²/(V s), respectively, as shown in the case of CH₃NH₃SnI₃ (<b>1</b>). We also compare the properties of the title hybrid materials with those of the “all-inorganic” CsSnI₃ and CsPbI₃ prepared using identical synthetic methods

Structure–Band Gap Relationships in Hexagonal Polytypes and Low-Dimensional Structures of Hybrid Tin Iodide Perovskites

The present study deals with the structural characterization and classification of the novel compounds <b>1</b>–<b>8</b> into perovskite subclasses and proceeds in extracting the structure–band gap relationships between them. The compounds were obtained from the employment of small, 3–5-atom-wide organic ammonium ions seeking to discover new perovskite-like compounds. The compounds reported here adopt unique or rare structure types akin to the prototype structure perovskite. When trimethylammonium (TMA) was employed, we obtained TMASnI₃ (<b>1</b>), which is our reference compound for a “perovskitoid” structure of face-sharing octahedra. The compounds EASnI₃ (<b>2b</b>), GASnI₃ (<b>3a</b>), ACASnI₃ (<b>4</b>), and IMSnI₃ (<b>5</b>) obtained from the use of ethylammonium (EA), guanidinium (GA), acetamidinium (ACA), and imidazolium (IM) cations, respectively, represent the first entries of the so-called “hexagonal perovskite polytypes” in the hybrid halide perovskite library. The hexagonal perovskites define a new family of hybrid halide perovskites with a crystal structure that emerges from a blend of corner- and face-sharing octahedral connections in various proportions. The small organic cations can also stabilize a second structural type characterized by a crystal lattice with reduced dimensionality. These compounds include the two-dimensional (2D) perovskites GA₂SnI₄ (<b>3b</b>) and IPA₃Sn₂I₇ (<b>6b</b>) and the one-dimensional (1D) perovskite IPA₃SnI₅ (<b>6a</b>). The known 2D perovskite BA₂MASn₂I₇ (<b>7</b>) and the related all-inorganic 1D perovskite “RbSnF₂I” (<b>8</b>) have also been synthesized. All compounds have been identified as medium-to-wide-band-gap semiconductors in the range of <i>E</i>_g = 1.90–2.40 eV, with the band gap progressively decreasing with increased corner-sharing functionality and increased torsion angle in the octahedral connectivity

Structure–Band Gap Relationships in Hexagonal Polytypes and Low-Dimensional Structures of Hybrid Tin Iodide Perovskites

The present study deals with the structural characterization and classification of the novel compounds <b>1</b>–<b>8</b> into perovskite subclasses and proceeds in extracting the structure–band gap relationships between them. The compounds were obtained from the employment of small, 3–5-atom-wide organic ammonium ions seeking to discover new perovskite-like compounds. The compounds reported here adopt unique or rare structure types akin to the prototype structure perovskite. When trimethylammonium (TMA) was employed, we obtained TMASnI₃ (<b>1</b>), which is our reference compound for a “perovskitoid” structure of face-sharing octahedra. The compounds EASnI₃ (<b>2b</b>), GASnI₃ (<b>3a</b>), ACASnI₃ (<b>4</b>), and IMSnI₃ (<b>5</b>) obtained from the use of ethylammonium (EA), guanidinium (GA), acetamidinium (ACA), and imidazolium (IM) cations, respectively, represent the first entries of the so-called “hexagonal perovskite polytypes” in the hybrid halide perovskite library. The hexagonal perovskites define a new family of hybrid halide perovskites with a crystal structure that emerges from a blend of corner- and face-sharing octahedral connections in various proportions. The small organic cations can also stabilize a second structural type characterized by a crystal lattice with reduced dimensionality. These compounds include the two-dimensional (2D) perovskites GA₂SnI₄ (<b>3b</b>) and IPA₃Sn₂I₇ (<b>6b</b>) and the one-dimensional (1D) perovskite IPA₃SnI₅ (<b>6a</b>). The known 2D perovskite BA₂MASn₂I₇ (<b>7</b>) and the related all-inorganic 1D perovskite “RbSnF₂I” (<b>8</b>) have also been synthesized. All compounds have been identified as medium-to-wide-band-gap semiconductors in the range of <i>E</i>_g = 1.90–2.40 eV, with the band gap progressively decreasing with increased corner-sharing functionality and increased torsion angle in the octahedral connectivity

Structure–Band Gap Relationships in Hexagonal Polytypes and Low-Dimensional Structures of Hybrid Tin Iodide Perovskites

The present study deals with the structural characterization and classification of the novel compounds <b>1</b>–<b>8</b> into perovskite subclasses and proceeds in extracting the structure–band gap relationships between them. The compounds were obtained from the employment of small, 3–5-atom-wide organic ammonium ions seeking to discover new perovskite-like compounds. The compounds reported here adopt unique or rare structure types akin to the prototype structure perovskite. When trimethylammonium (TMA) was employed, we obtained TMASnI₃ (<b>1</b>), which is our reference compound for a “perovskitoid” structure of face-sharing octahedra. The compounds EASnI₃ (<b>2b</b>), GASnI₃ (<b>3a</b>), ACASnI₃ (<b>4</b>), and IMSnI₃ (<b>5</b>) obtained from the use of ethylammonium (EA), guanidinium (GA), acetamidinium (ACA), and imidazolium (IM) cations, respectively, represent the first entries of the so-called “hexagonal perovskite polytypes” in the hybrid halide perovskite library. The hexagonal perovskites define a new family of hybrid halide perovskites with a crystal structure that emerges from a blend of corner- and face-sharing octahedral connections in various proportions. The small organic cations can also stabilize a second structural type characterized by a crystal lattice with reduced dimensionality. These compounds include the two-dimensional (2D) perovskites GA₂SnI₄ (<b>3b</b>) and IPA₃Sn₂I₇ (<b>6b</b>) and the one-dimensional (1D) perovskite IPA₃SnI₅ (<b>6a</b>). The known 2D perovskite BA₂MASn₂I₇ (<b>7</b>) and the related all-inorganic 1D perovskite “RbSnF₂I” (<b>8</b>) have also been synthesized. All compounds have been identified as medium-to-wide-band-gap semiconductors in the range of <i>E</i>_g = 1.90–2.40 eV, with the band gap progressively decreasing with increased corner-sharing functionality and increased torsion angle in the octahedral connectivity

Anomalous Band Gap Behavior in Mixed Sn and Pb Perovskites Enables Broadening of Absorption Spectrum in Solar Cells

Perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research and development because of their promise for high-power conversion efficiencies and ease of fabrication. Two types of generic perovskites compounds have been used in cell fabrication: either Pb- or Sn-based. Here, we describe the performance of perovskite solar cells based on alloyed perovskite solid solutions of methylammonium tin iodide and its lead analogue (CH₃NH₃Sn_1–<i>x</i>Pb_<i>x</i>I₃). We exploit the fact that, the energy band gaps of the mixed Pb/Sn compounds do not follow a linear trend (the Vegard’s law) in between these two extremes of 1.55 and 1.35 eV, respectively, but have narrower bandgap (<1.3 eV), thus extending the light absorption into the near-infrared (∼1,050 nm). A series of solution-processed solid-state photovoltaic devices using a mixture of organic spiro-OMeTAD/lithium bis­(trifluoromethylsulfonyl)­imide/pyridinium additives as hole transport layer were fabricated and studied as a function of Sn to Pb ratio. Our results show that CH₃NH₃Sn_0.5Pb_0.5I₃ has the broadest light absorption and highest short-circuit photocurrent density ∼20 mA cm^–2 (obtained under simulated full sunlight of 100 mW cm^–2)

Directional Negative Thermal Expansion and Large Poisson Ratio in CH₃NH₃PbI₃ Perovskite Revealed by Strong Coherent Shear Phonon Generation

Despite the enormous amount of attention CH₃NH₃PbI₃ has received, we are still lacking an in-depth understanding of its basic properties. In particular, the directional mechanical and structural characteristics of this material have remained elusive. Here, we investigate these properties by monitoring the propagation of longitudinal and shear phonons following the absorption of a femtosecond pulse along various crystalline directions of a CH₃NH₃PbI₃ single crystal. We first extract the sound velocities of longitudinal and transverse phonons along these directions of the crystal. Our study then reveals the negative directional thermal expansion of CH₃NH₃PbI₃, which is responsible for strong coherent shear phonon generation. Finally, from these observations, we perform elastic characterization of this material, revealing a large directional Poisson’s ratio, which reaches 0.7 and that we associate with the weak mechanical stability of this material. Our results also provide guidelines to fabricate a transducer of high-frequency transverse phonons