Role of surface passivating ligand and growth temperature on the size quantization effects of colloidal hybrid (MEH-PPV/P3HT:PbSe) nanocomposites

In this work, it has been demonstrated that a systematic combination of the reaction and growth conditions allows the possibility to produce high quality PbSe nanocrystals over a broad range of diameters with narrow size distributions without resorting to any size selective precipitation techniques. Effect of capping agents and critical growth parameters such as injection and growth temperature on the morphology of PbSe nanocrystallites is analyzed and discussed in terms of Efros'effective mass approximation theory and Wang's hyperbolic band model respectively. It is found that a hyperbolic Wang's band model is sufficiently accurate to explain the size quantization effects of PbSe nanocrystals. The capping agent/ligand (tri-n-octylphosphine and oleic acid mixture) helps to control the grain growth of the nanocrystals during its formation and increases the dispersibility of the nanocrystals in conducting polymer matrices viz. poly[2-methoxy, 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly(3-hexylthiophene) (P3HT) for its application in photovoltaics.