Atomic-scale insight into the enhanced surface stability of methylammonium lead iodide perovskite by controlled deposition of lead chloride

The incorporation of a certain amount of Cl ions into methylammonium lead iodide (MAPbI3) perovskite films and how these incorporated Cl ions affect the structural and electronic properties of these films have been an intensively studied topic. In this study, we comprehensively investigated Cl incorporation in MAPbI3 at the atomic scale by a combined study of scanning tunneling microscopy, X-ray photoelectron spectroscopy, ultraviolet and inverse photoemission spectroscopy, density functional theory and molecular dynamics calculations. At a Cl concentration of 14.8 ± 0.6%, scanning tunneling microscopy images confirm the incorporation of Cl ions on the MAPbI3 surface, which also corresponds to the highest surface stability of MAPbI3 found from the viewpoint of both thermodynamics and kinetics by density functional theory and molecular dynamics calculations. Our results show that the Cl concentration is crucial to the surface bandgap and stability of MAPbI3

Nanostructured Bi2S3encapsulated within three-dimensional N-doped graphene as active and flexible anodes for sodium-ion batteries

Sodium-ion batteries (SIBs) have been increasingly attracting attention as a sustainable alternative to lithium-ion batteries for scalable energy storage. The key to advanced SIBs relies heavily upon the development of reliable anodes. In this respect, Bi 2 S 3 has been extensively investigated because of its high capacity, tailorable morphology, and low cost. However, the common practices of incorporating carbon species to enhance the electrical conductivity and accommodate the volume change of Bi 2 S 3 anodes so as to boost their durability for Na storage have met with limited success. Herein, we report a simple method to realize the encap sulation of Bi 2 S 3 nanorods within three-dimensional, nitrogen-doped graphene (3DNG) frameworks, targeting flexible and active composite anodes for SIBs. The Bi 2 S 3 /3DNG composites displayed outstanding Na storage behavior with a high reversible capacity (649 mAh·g -1 at 62.5 mA·g -1 ) and favorable durability (307 and 200 mAh·g -1 after 100 cycles at 125 and 312.5 mA·g -1 , respectively). In-depth characterization by in situ X-ray diffraction revealed that the intriguing Na storage process of Bi 2 S 3 was based upon a reversible reaction. Furthermore, a full, flexible SIB cell with Na 0.4 MnO 2 cathode and as-prepared composite anode was successfully assembled, and holds a great promise for next-generation, wearable energy storage applications. [Figure not available: see fulltext.

Confining MOF-derived SnSe nanoplatelets in nitrogen-doped graphene cages via direct CVD for durable sodium ion storage

Tin-based compounds are deemed as suitable anode candidates affording promising sodium-ion storages for rechargeable batteries and hybrid capacitors. However, synergistically tailoring the electrical conductivity and structural stability of tin-based anodes to attain durable sodium-ion storages remains challenging to date for its practical applications. Herein, metal-organic framework (MOF) derived SnSe/C wrapped within nitrogen-doped graphene (NG@SnSe/C) is designed targeting durable sodium-ion storage. NG@SnSe/C possesses favorable electrical conductivity and structure stability due to the “inner” carbon framework from the MOF thermal treatment and “outer” graphitic cage from the direct chemical vapor deposition synthesis. Consequently, NG@SnSe/C electrode can obtain a high reversible capacity of 650 mAh·g−1 at 0.05 A·g−1, a favorable rate performance of 287.8 mAh·g−1 at 5 A·g−1 and a superior cycle stability with a negligible capacity decay of 0.016% per cycle over 3,200 cycles at 0.4 A·g−1. Theoretical calculations reveal that the nitrogen-doping in graphene can stabilize the NG@SnSe/C structure and improve the electrical conductivity. The reversible Na-ion storage mechanism of SnSe is further investigated by in-situ X-ray diffraction/ex-situ transmission electron microscopy. Furthermore, assembled sodium-ion hybrid capacitor full-cells comprising our NG@SnSe/C anode and an active carbon cathode harvest a high energy/power density of 115.5 Wh·kg−1/5,742 W·kg−1, holding promise for next-generation energy storages.[Figure not available: see fulltext.]

Device Performance of the Mott Insulator LaVO 3 as a Photovoltaic Material

International audienceSearching for solar-absorbing materials containing earth-abundant elements with chemical stability is of critical importance for advancing photovoltaic technologies. Mott insulators have been theoretically proposed as potential photovoltaic materials. In this paper, we evaluate their performance in solar cells by exploring the photovoltaic properties of Mott insulator LaVO3 (LVO). LVO films show an indirect band gap of 1.08 eV as well as strong light absorption over a wide wavelength range in the solar spectrum. First-principles calculations on the band structure of LVO further reveal that the d−d transitions within the upper and lower Mott-Hubbard bands and p−d transitions between the O 2p and V 3d band contribute to the absorption in visible and ultraviolet ranges, respectively. Transport measurements indicate strong carrier trapping and the formation of polarons in LVO. To utilize the strong light absorption of LVO and to overcome its poor carrier transport, we incorporate it as a light absorber in solar cells in conjunction with carrier transporters and evaluate its device performance. Our complementary experimental and theoretical results on such prototypical solar cells made of Mott-Hubbard transition-metal oxides pave the road for developing light-absorbing materials and photovoltaic devices based on strongly correlated electrons

Device Performance of the Mott Insulator LaVO 3 as a Photovoltaic Material

International audienceSearching for solar-absorbing materials containing earth-abundant elements with chemical stability is of critical importance for advancing photovoltaic technologies. Mott insulators have been theoretically proposed as potential photovoltaic materials. In this paper, we evaluate their performance in solar cells by exploring the photovoltaic properties of Mott insulator LaVO3 (LVO). LVO films show an indirect band gap of 1.08 eV as well as strong light absorption over a wide wavelength range in the solar spectrum. First-principles calculations on the band structure of LVO further reveal that the d−d transitions within the upper and lower Mott-Hubbard bands and p−d transitions between the O 2p and V 3d band contribute to the absorption in visible and ultraviolet ranges, respectively. Transport measurements indicate strong carrier trapping and the formation of polarons in LVO. To utilize the strong light absorption of LVO and to overcome its poor carrier transport, we incorporate it as a light absorber in solar cells in conjunction with carrier transporters and evaluate its device performance. Our complementary experimental and theoretical results on such prototypical solar cells made of Mott-Hubbard transition-metal oxides pave the road for developing light-absorbing materials and photovoltaic devices based on strongly correlated electrons

Device Performance of the Mott Insulator LaVO 3 as a Photovoltaic Material

International audienc