There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

We demonstrate that metal carboxylate complexes (L–M(O2CR)2, R = oleyl, tetradecyl, M = Cd, Pb) are readily displaced from carboxylate-terminated ME nanocrystals (ME = CdSe, CdS, PbSe, PbS) by various Lewis bases (L = tri-n-butylamine, tetrahydrofuran, tetradecanol, N,N-dimethyl-n-butylamine, tri-n-butylphosphine, N,N,N′,N′-tetramethylbutylene-1,4-diamine, pyridine, N,N,N′,N′-tetramethylethylene-1,2-diamine, n-octylamine). The relative displacement potency is measured by 1H NMR spectroscopy and depends most strongly on geometric factors such as sterics and chelation, although also on the hard/soft match with the cadmium ion. The results suggest that ligands displace L–M(O2CR)2 by cooperatively complexing the displaced metal ion as well as the nanocrystal. Removal of up to 90% of surface-bound Cd(O2CR)2 from CdSe and CdS nanocrystals decreases the Cd/Se ratio from 1.1 ± 0.06 to 1.0 ± 0.05, broadens the 1Se–2S3/2h absorption, and decreases the photoluminescence quantum yield (PLQY) from 10% to <1% (CdSe) an...

/pdf/ligand-exchange-and-the-stoichiometry-of-metal-chalcogenide-mvgek5d5ry.pdf

Ligand exchange and the stoichiometry of metal chalcogenide nanocrystals: spectroscopic observation of facile metal-carboxylate displacement and binding.

All-inorganic cesium lead halide (CsPbX3, X = Br–, I–) perovskites could potentially provide comparable photovoltaic performance with enhanced stability compared to organic–inorganic lead halide species. However, small-bandgap cubic CsPbI3 has been difficult to study due to challenges forming CsPbI3 in the cubic phase. Here, a low-temperature procedure to form cubic CsPbI3 has been developed through a halide exchange reaction using films of sintered CsPbBr3 nanocrystals. The reaction was found to be strongly dependent upon temperature, featuring an Arrhenius relationship. Additionally, film thickness played a significant role in determining internal film structure at intermediate reaction times. Thin films (50 nm) showed only a small distribution of CsPbBrxI3–x species, while thicker films (350 nm) exhibited much broader distributions. Furthermore, internal film structure was ordered, featuring a compositional gradient within film. Transient absorption spectroscopy showed the influence of halide exchange ...

http://pubs.acs.org/doi/pdf/10.1021/jacs.6b04661

Transformation of Sintered CsPbBr3 Nanocrystals to Cubic CsPbI3 and Gradient CsPbBrxI3-x through Halide Exchange.

http://users.encs.concordia.ca/~mojtaba/elec6271/Colloidal%20quantum%20dot%20solar%20cells.pdf

Colloidal quantum dot solar cells

Recent advances in eco-friendly and cost-effective materials towards sustainable dye-sensitized solar cells

TOPO- and pyridine-capped cubic CdSe quantum dots were prepared, and the effect of surface ligand exchange on the photoluminescence (PL) peak shift was investigated. From the analysis of PL spectra and TEM images, it was found that the decrease in diameter in the CdSe quantum dot and redistribution of its surface electronic density play different roles in the PL peak shift. The reduction in size of CdSe by ligand exchange caused a blue shift of the PL peak due to the quantum confinement effect, whereas the redistribution of surface electronic density of CdSe by the exchange of TOPO with pyridine resulted in a red shift of 23 meV on the average for the samples investigated. The result was also supported by the XPS characterizations.

Photoluminescence Blue-Shift of CdSe Nanoparticles Caused by Exchange of Surface Capping Layer

Improvement of CdSe/P3HT bulk hetero-junction solar cell performance due to ligand exchange from TOPO to pyridine

Iron pyrite: Phase and shape control by facile hot injection method

Effect of CdSe/P3HT composition on electrical and structural properties of bulk hetero-junction solar cell active layer

SnS nanospheres (NSPs) were synthesized, and the effects of thermal annealing on the structural, morphological, chemical compositional and optical properties were examined. As-synthesized SnS NPSs with a mean size of 3-4 nm underwent a solid state morphological transformation by high temperature annealing in a nitrogen environment. Upon annealing, the size of SnS NSP increased to 5-6 nm with enhanced crystallinity. Also, the photoluminescence (PL) of the nitrogen-annealed samples slightly decreased in intensity with accompanying red-shift in spectrum. The power conversion efficiency of the solar cells using a polymer and the SnS NSPs was ~0.71%. These results confirm that the SnS NSPs demonstrate a potential as an inorganic material to be used in organic-inorganic hybrid bulk heterojunction (BHJ) photovoltaic devices.

Nguyen Tam Nguyen Truong

Papers

Photoluminescence Blue-Shift of CdSe Nanoparticles Caused by Exchange of Surface Capping Layer

Improvement of CdSe/P3HT bulk hetero-junction solar cell performance due to ligand exchange from TOPO to pyridine

Iron pyrite: Phase and shape control by facile hot injection method

Effect of CdSe/P3HT composition on electrical and structural properties of bulk hetero-junction solar cell active layer

Effect of post-synthesis annealing on properties of SnS nanospheres and its solar cell performance