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Ionic transport in hybrid lead iodide perovskite solar cells.

Eames C, Frost JM, Barnes PR, O'Regan BC, Walsh A, Islam MS - Nat Commun (2015)

Bottom Line: Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear.Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extracted from the current-voltage response of a perovskite-based solar cell.We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6 eV, in good agreement with the kinetic measurements.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Bath, Bath BA2 7AY, UK.

ABSTRACT
Solar cells based on organic-inorganic halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behaviour such as current-voltage hysteresis and a low-frequency giant dielectric response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extracted from the current-voltage response of a perovskite-based solar cell. We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6‚ÄČeV, in good agreement with the kinetic measurements. The results of this combined computational and experimental study suggest that hybrid halide perovskites are mixed ionic-electronic conductors, a finding that has major implications for solar cell device architectures.

No MeSH data available.


Related in: MedlinePlus

Iodide ion vacancy migration from density functional theory calculations.(a) Calculated migration path indicating a slightly curved path and local relaxation/tilting of the octahedra. (b) Corresponding energy profile.
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f3: Iodide ion vacancy migration from density functional theory calculations.(a) Calculated migration path indicating a slightly curved path and local relaxation/tilting of the octahedra. (b) Corresponding energy profile.

Mentions: With regard to mechanistic features, it is often assumed that the migrating ion takes the shortest path between adjacent sites, that is, a direct linear jump. However, detailed analysis of the migration paths for the iodide ion vacancy mechanism reveals a small deviation from the linear route involving a curved path between iodine sites, with the saddle point slightly bowed away from the neighbouring Pb ion (shown in Fig. 3 together with the corresponding energy profile); such an atomic-scale mechanism is difficult to extract from an experiment alone. It is worth noting that analogous curved paths have been found from both atomistic simulation52 and neutron diffraction studies3357 of oxide-ion conduction in inorganic perovskite oxides such as doped LaGaO3. Similar mechanisms may feature in related hybrid halide perovskites.


Ionic transport in hybrid lead iodide perovskite solar cells.

Eames C, Frost JM, Barnes PR, O'Regan BC, Walsh A, Islam MS - Nat Commun (2015)

Iodide ion vacancy migration from density functional theory calculations.(a) Calculated migration path indicating a slightly curved path and local relaxation/tilting of the octahedra. (b) Corresponding energy profile.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4491179&req=5

f3: Iodide ion vacancy migration from density functional theory calculations.(a) Calculated migration path indicating a slightly curved path and local relaxation/tilting of the octahedra. (b) Corresponding energy profile.
Mentions: With regard to mechanistic features, it is often assumed that the migrating ion takes the shortest path between adjacent sites, that is, a direct linear jump. However, detailed analysis of the migration paths for the iodide ion vacancy mechanism reveals a small deviation from the linear route involving a curved path between iodine sites, with the saddle point slightly bowed away from the neighbouring Pb ion (shown in Fig. 3 together with the corresponding energy profile); such an atomic-scale mechanism is difficult to extract from an experiment alone. It is worth noting that analogous curved paths have been found from both atomistic simulation52 and neutron diffraction studies3357 of oxide-ion conduction in inorganic perovskite oxides such as doped LaGaO3. Similar mechanisms may feature in related hybrid halide perovskites.

Bottom Line: Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear.Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extracted from the current-voltage response of a perovskite-based solar cell.We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6 eV, in good agreement with the kinetic measurements.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Bath, Bath BA2 7AY, UK.

ABSTRACT
Solar cells based on organic-inorganic halide perovskites have recently shown rapidly rising power conversion efficiencies, but exhibit unusual behaviour such as current-voltage hysteresis and a low-frequency giant dielectric response. Ionic transport has been suggested to be an important factor contributing to these effects; however, the chemical origin of this transport and the mobile species are unclear. Here, the activation energies for ionic migration in methylammonium lead iodide (CH3NH3PbI3) are derived from first principles, and are compared with kinetic data extracted from the current-voltage response of a perovskite-based solar cell. We identify the microscopic transport mechanisms, and find facile vacancy-assisted migration of iodide ions with an activation energy of 0.6‚ÄČeV, in good agreement with the kinetic measurements. The results of this combined computational and experimental study suggest that hybrid halide perovskites are mixed ionic-electronic conductors, a finding that has major implications for solar cell device architectures.

No MeSH data available.


Related in: MedlinePlus