The CdSe NCs were produced with a fixed Cd/Se molar ratio of 2:1 and using 2.32 g of trioctylphosphine oxide (TOPO); at the same time, all the trioctylphosphine selenide (TOPSe) injections were kept at 1 ml, but with different concentrations. No other ligands were used in the case study.

Homogeneous CdSe NCs with different morphology were obtained under such experimental conditions. The sample quality (size distribution, optical properties, tetrapod selectivity) is as good as that of the best CdSe NCs synthesized by using extra ligands. As for the growth mechanism, we believed that the decomposition of TOPSe and cadmium myristate at a temperature of 240 or 300 °C would also supply in situ-generated TOP and myristic acid in the reaction mixture, which affected the anisotropic growth of CdSe NCs.

To further investigate the application of this surfactant-free recipe, the group is now optimizing the experimental conditions and has found that well controlled morphology of CdTe and/or CdSexTe1–x NCs can also be successfully fabricated.

Thanks to the easily controllable NC-growth kinetics, such a synthesis route is very promising for low cost, large-scale preparation of CdSe and CdTe NCs for application in solution-processed thin-film solar cells.

More information can be found in the journal Nanotechnology.