scholarly journals Reconfiguring the band-edge states of photovoltaic perovskites by conjugated organic cations

Science ◽  
2021 ◽  
Vol 371 (6529) ◽  
pp. 636-640
Author(s):  
Jingjing Xue ◽  
Rui Wang ◽  
Xihan Chen ◽  
Canglang Yao ◽  
Xiaoyun Jin ◽  
...  
Keyword(s):  
Edge States ◽  
Frontier Orbitals ◽  
Halide Anion ◽  
Surface Band ◽  
Device Stability ◽  
General Chemical ◽  
Halide Perovskites ◽  
Inorganic Framework ◽  
A Site ◽  
Conversion Efficiencies

The band edges of metal-halide perovskites with a general chemical structure of ABX3 (A, usually a monovalent organic cation; B, a divalent cation; and X, a halide anion) are constructed mainly of the orbitals from B and X sites. Hence, the structural and compositional varieties of the inorganic B–X framework are primarily responsible for regulating their electronic properties, whereas A-site cations are thought to only help stabilize the lattice and not to directly contribute to near-edge states. We report a π-conjugation–induced extension of electronic states of A-site cations that affects perovskite frontier orbitals. The π-conjugated pyrene-containing A-site cations electronically contribute to the surface band edges and influence the carrier dynamics, with a properly tailored intercalation distance between layers of the inorganic framework. The ethylammonium pyrene increased hole mobilities, improved power conversion efficiencies relative to that of a reference perovskite, and enhanced device stability.

scholarly journals Synthetic Variation and Structural Trends in Layered Two-Dimensional Alkylammonium Lead Halide Perovskites

2019 ◽  
Author(s):  
Watcharaphol Paritmongkol ◽  
Nabeel Dahod ◽  
Nannan Mao ◽  
Shao-Liang Zheng ◽  
William Tisdale
Keyword(s):  
Crystal Structures ◽  
Periodic Variation ◽  
Two Dimensional ◽  
Halide Anion ◽  
Structural Distortions ◽  
Spacer Layer ◽  
Halide Perovskites ◽  
Spacer Chain Length ◽  
A Site ◽  
Lead Halide

We report the cooling-induced crystallization of layered two-dimensional lead halide perovskites with controllable inorganic quantum-well thickness (<i>n</i> = 1, 2, 3, 4)<i>,</i> organic spacer chain length (butyl-, pentyl-, hexylammonium), A-site cation (methylammonium, formamidinium), and halide anion (iodide, bromide). We report crystal structures for the iodide family as a function of these compositional parameters, and across their temperature dependent phase transitions. In general, lower symmetry crystal structures, increasing extents of organic-spacer interdigitation, and increasing organic-spacer corrugation tilts are observed at low temperature. In addition, greater structural distortions are seen in lead halide octahedra closest to the organic spacer layer, and larger-<i>n­ </i>structures exhibit periodic variation in Pb-I bond lengths. We also provide detailed guidance regarding the combination of synthetic parameters needed to achieve phase-pure crystals of each composition, and discuss difficulties encountered when trying to synthesize particular members of the 2D perovskite family containing formamidinium or cesium as the A-site cation. These results provide a foundation for understanding structural trends in 2D lead halide perovskites and the effect these trends have on their thermal, electrical, and optical properties.

scholarly journals Synthetic Variation and Structural Trends in Layered Two-Dimensional Alkylammonium Lead Halide Perovskites

2019 ◽  
Author(s):  
Watcharaphol Paritmongkol ◽  
Nabeel Dahod ◽  
Nannan Mao ◽  
Shao-Liang Zheng ◽  
William Tisdale
Keyword(s):  
Crystal Structures ◽  
Periodic Variation ◽  
Two Dimensional ◽  
Halide Anion ◽  
Structural Distortions ◽  
Spacer Layer ◽  
Halide Perovskites ◽  
Spacer Chain Length ◽  
A Site ◽  
Lead Halide

We report the cooling-induced crystallization of layered two-dimensional lead halide perovskites with controllable inorganic quantum-well thickness (<i>n</i> = 1, 2, 3, 4)<i>,</i> organic spacer chain length (butyl-, pentyl-, hexylammonium), A-site cation (methylammonium, formamidinium), and halide anion (iodide, bromide). We report crystal structures for the iodide family as a function of these compositional parameters, and across their temperature dependent phase transitions. In general, lower symmetry crystal structures, increasing extents of organic-spacer interdigitation, and increasing organic-spacer corrugation tilts are observed at low temperature. In addition, greater structural distortions are seen in lead halide octahedra closest to the organic spacer layer, and larger-<i>n­ </i>structures exhibit periodic variation in Pb-I bond lengths. We also provide detailed guidance regarding the combination of synthetic parameters needed to achieve phase-pure crystals of each composition, and discuss difficulties encountered when trying to synthesize particular members of the 2D perovskite family containing formamidinium or cesium as the A-site cation. These results provide a foundation for understanding structural trends in 2D lead halide perovskites and the effect these trends have on their thermal, electrical, and optical properties.

scholarly journals Electronic Properties of Triangle Molybdenum Disulfide (MoS2) Clusters with Different Sizes and Edges

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1157
Author(s):  
Songsong Wang ◽  
Changliang Han ◽  
Liuqi Ye ◽  
Guiling Zhang ◽  
Yangyang Hu ◽  
...  
Keyword(s):  
Quantum Chemistry ◽  
Electronic Properties ◽  
Absorption Spectra ◽  
Molecular Orbital ◽  
Electronic Structures ◽  
Edge States ◽  
Frontier Orbitals ◽  
Edge Structure ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

The electronic structures and transition properties of three types of triangle MoS2 clusters, A (Mo edge passivated with two S atoms), B (Mo edge passivated with one S atom), and C (S edge) have been explored using quantum chemistry methods. The highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap of B and C is larger than that of A, due to the absence of the dangling of edge S atoms. The frontier orbitals (FMOs) of A can be divided into two categories, edge states from S3p at the edge and hybrid states of Mo4d and S3p covering the whole cluster. Due to edge/corner states appearing in the FMOs of triangle MoS2 clusters, their absorption spectra show unique characteristics along with the edge structure and size.

scholarly journals Colloidal Synthesis of Lead-free Cs2TiBr6-xIx Perovskite Nanocrystals

2021 ◽  
Author(s):  
Shanti Maria Liga ◽  
Gerasimos Konstantatos
Keyword(s):  
Solar Cells ◽  
Power Conversion ◽  
Lead Free ◽  
Colloidal Synthesis ◽  
Optoelectronic Materials ◽  
Perovskite Nanocrystals ◽  
Halide Perovskites ◽  
Conversion Efficiencies

Cesium titanium halide perovskites are novel lead-free optoelectronic materials that have attracted attention in the last two years for their application in solar cells with power conversion efficiencies reaching 3.3%....

A study on the effects of mixed organic cations on the structure and properties in lead halide perovskites

2020 ◽  
Vol 22 (5) ◽  
pp. 3105-3111 ◽  
Author(s):  
Chao Wu ◽  
Daoyou Guo ◽  
Peigang Li ◽  
Shunli Wang ◽  
Aiping Liu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Single Crystals ◽  
Electrical Transport ◽  
Organic Cation ◽  
Organic Cations ◽  
Structure And Properties ◽  
Electrical Transport Properties ◽  
Halide Perovskites ◽  
A Site ◽  
Lead Halide

Four types of organic cation-mixed single crystals were successfully synthesized by partially substituting A site cations to investigate the effect of organic cations on structure, optical features, thermal stability, and electrical transport properties.

scholarly journals Understanding the interplay of stability and efficiency in A-site engineered lead halide perovskites

APL Materials ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 070901 ◽  
Author(s):  
Feray Ünlü ◽  
Eunhwan Jung ◽  
Jinane Haddad ◽  
Ashish Kulkarni ◽  
Senol Öz ◽  
...  
Keyword(s):  
Halide Perovskites ◽  
A Site ◽  
Lead Halide

Extrinsic and Dynamic Edge States of Two-Dimensional Lead Halide Perovskites

ACS Nano ◽  
2019 ◽  
Author(s):  
Enzheng Shi ◽  
Shibin Deng ◽  
Biao Yuan ◽  
Yao Gao ◽  
Akriti ◽  
...  
Keyword(s):  
Two Dimensional ◽  
Edge States ◽  
Halide Perovskites ◽  
Lead Halide

scholarly journals Chemical tuning of dynamic cation off-centering in the cubic phases of hybrid tin and lead halide perovskites

2017 ◽  
Vol 8 (8) ◽  
pp. 5628-5635 ◽  
Author(s):  
Geneva Laurita ◽  
Douglas H. Fabini ◽  
Constantinos C. Stoumpos ◽  
Mercouri G. Kanatzidis ◽  
Ram Seshadri
Keyword(s):  
Dielectric Properties ◽  
Cubic Phases ◽  
Halide Perovskites ◽  
Inorganic Framework ◽  
Lead Halide

We reveal here a key aspect of the inorganic framework of hybrid halide perovskites that potentially impacts the electronic, thermal, and dielectric properties.

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