| 1. |
- Baias, Maria, et al.
(author)
-
De Novo Determination of the Crystal Structure of a Large Drug Molecule by Crystal Structure Prediction-Based Powder NMR Crystallography
- 2013
-
In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 135:46, s. 17501-17507
-
Journal article (peer-reviewed)abstract
- The crystal structure of form 4 of the drug 4-[4-(2-adamantylcarbamoyl)-5-tert-butyl-pyrazol-1-yl]benzoic acid is determined using a protocol for NMR powder crystallography at natural isotopic abundance combining solid-state H-1 NMR spectroscopy, crystal structure prediction, and density functional theory chemical shift calculations. This is the first example of NMR crystal structure determination for a molecular compound of previously unknown structure, and at 422 g/mol this is the largest compound to which this method has been applied so far.
|
|
| 2. |
- Cadars, Sylvian, et al.
(author)
-
Dynamics and disorder in surfactant-templated silicate layers studied by solid-state NMR dephasing times and correlated line shapes
- 2008
-
In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:25, s. 9145-9154
-
Journal article (peer-reviewed)abstract
- Surfactant-templated layered silicates are shown to possess complex compositional, structural, and dynamic features that manifest rich and interrelated order and disorder at molecular length scales. Temperature-dependent 1D and 2D solid-state Si-29 NMR measurements reveal a chemical-exchange process involving the surfactant headgroups that is concomitant with reversible broadening of Si-29 NMR line shapes under magic-angle-spinning (MAS) conditions at temperatures in the range 205-330 K. Specifically, the temperature-dependent changes in the Si-29 transverse dephasing times T-2' can be quantitatively accounted for by 2-fold reorientational dynamics of the surfactant headgroups. Variable-temperature analyses demonstrate that the temperature-dependent Si-29 shifts, peak broadening, and 2D Si-29{Si-29} correlation NMR line shapes are directly related to the freezing of the surfactant headgroup dynamics, which results in local structural disorder within the silicate framework.
|
|
| 3. |
- Jeong, Jaeki, et al.
(author)
-
Pseudo-halide anion engineering for α-FAPbI3 perovskite solar cells
- 2021
-
In: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 592:7854, s. 381-385
-
Journal article (peer-reviewed)abstract
- Metal halide perovskites of the general formula ABX(3)-where A is a monovalent cation such as caesium, methylammonium or formamidinium; B is divalent lead, tin or germanium; and X is a halide anion-have shown great potential as light harvesters for thin-film photovoltaics(1-5). Among a large number of compositions investigated, the cubic a-phase of formamidinium lead triiodide (FAPbI(3)) hasemerged as the most promising semiconductor for highly efficient and stable perovskite solar cells(6-9), and maximizing the performance of this material in such devices is of vital importance for the perovskite researchcommunity. Here we introduce an anion engineering concept that uses the pseudo-halide anion formate (HCOO-) to suppress anion-vacancy defects that are present at grain boundaries and at the surface of the perovskite films and to augment the crystallinity of the films. Theresulting solar cell devices attain a power conversion efficiency of 25.6 per cent (certified 25.2 per cent), have long-term operational stability (450 hours) and show intense electroluminescence with external quantum efficiencies of more than 10 per cent. Our findings provide a direct route to eliminate the most abundant and deleterious lattice defects present in metal halide perovskites, providing a facile access to solution-processable films with improved optoelectronic performance.
|
|
| 4. |
- Xie, Haibing, et al.
(author)
-
Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells
- 2021
-
In: Joule. - : CELL PRESS. - 2542-4351. ; 5:5, s. 1246-1266
-
Journal article (peer-reviewed)abstract
- Understanding defects is of paramount importance for the development of stable halide perovskite solar cells (PSCs). However, isolating their distinctive effects on device efficiency and stability is currently a challenge. We report that adding the organic molecule 3-phosphonopropionic acid (H3pp) to the halide perovskite results in unchanged overall optoelectronic performance while having a tremendous effect on device stability. We obtained PSCs with similar to 21% efficiency that retain similar to 100% of the initial efficiency after 1,000 h at the maximum power point under simulated AM1.5G illumination. The strong interaction between the perovskite and the H3pp molecule through two types of hydrogen bonds (H center dot center dot center dot I and O center dot center dot center dot H) leads to shallow point defect passivation that has a significant effect on device stability but not on the non-radiative recombination and device efficiency. We expect that our work will have important implications for the current understanding and advancement of operational PSCs.
|
|
| 5. |
- Zhang, Hong, et al.
(author)
-
Multimodal host-guest complexation for efficient and stable perovskite photovoltaics
- 2021
-
In: Nature Communications. - : Springer Nature. - 2041-1723. ; 12:1
-
Journal article (peer-reviewed)abstract
- Formamidinium lead iodide perovskites are promising light-harvesting materials, yet stabilizing them under operating conditions without compromising optimal optoelectronic properties remains challenging. We report a multimodal host-guest complexation strategy to overcome this challenge using a crown ether, dibenzo-21-crown-7, which acts as a vehicle that assembles at the interface and delivers Cs+ ions into the interior while modulating the material. This provides a local gradient of doping at the nanoscale that assists in photoinduced charge separation while passivating surface and bulk defects, stabilizing the perovskite phase through a synergistic effect of the host, guest, and host-guest complex. The resulting solar cells show power conversion efficiencies exceeding 24% and enhanced operational stability, maintaining over 95% of their performance without encapsulation for 500h under continuous operation. Moreover, the host contributes to binding lead ions, reducing their environmental impact. This supramolecular strategy illustrates the broad implications of host-guest chemistry in photovoltaics. It remains a challenge to achieve a balance between performance and stability, as well as addressing the environmental impact of perovskite solar cells. Here, the authors propose a multimodal host-guest complexation strategy enabling these shortcomings to be addressed simultaneously.
|
|
