Recent developments in colloidal synthesis of CuInSe2 nanoparticles.

Ternary semiconductor nanocrystals, such as CuInSe2 , are of high interest for photovoltaic application due to their relatively low toxicity and unique properties. During the last decades great success has been achieved in the colloidal synthesis of binary nanoparticles, but for ternary compounds this research is still in an early stage of development. These materials are a challenge for synthetic chemistry, because the interaction between the three components (copper, indium, and selenium) plays a major role for the production of high quality material. The purpose of this Minireview is to provide a summary of the achievements in colloidal synthesis of CuInSe2 nanoparticles--in particular, details of reaction mechanism and its characterization possibilities, which might be useful also for the colloidal synthesis of other multicomponent systems.

Synthesis of lead chalcogenide nanocrystals and study of charge transfer in blends of PbSe nanocrystals and poly(3-hexylthiophene).

Nearly monodisperse lead chalcogenide (PbE, E = S, Se, or Te) semiconductor quantum dots of controllable shape have been produced via a novel synthesis which includes the occurrence of in situ formed Pb(0) particles. Tunable size and shape are achieved through appropriate choice of the precursor type and the stabilizer. As precursor, we use, on the one hand, lead oxide or lead acetate, on the other hand, tellurium, selenium, or sulfur powder dissolved in trioctylphosphine (TOP), tributylphosphine (TBP), or 1-octadecene (ODE). Oleic acid (OA) and various amines, as well as TOP and TBP are used for stabilization. With respect to possible application in hybrid solar cells, the surface of as-synthesized spherical PbSe nanocrystals was investigated by nuclear magnetic resonance (NMR), mass spectrometry (MS) and thermogravimetric analysis (TGA). As an important result, it was found that the surface is not mostly covered by oleic acid after synthesis, but by a phosphorus compound. We also applied a ligand exchange procedure with hexylamine and found evidence for the successful attachment of hexylamine to the nanocrystal surface. Additionally, charge separation between these nanoparticles and the conjugated polymer poly(3-hexylthiophene) (P3HT) is studied by electron spin resonance and photoinduced absorption spectroscopy. The spectra obtained suggest that charges can be produced successfully by photoinduced charge transfer.