Growth orientation, shape evolution of monodisperse PbSe nanocrystals and their use in optoelectronic devices

A new facile solution method for the synthesis of high quality lead selenide (PbSe) nanocrystals with controllable size and shape was developed. A Pb–stearate complex and oleylamine–selenium (OLA–Se) were used as new precursors to prepare monodispersed nanocrystals instead of the traditional lead oxide (PbO) and trioctylphosphine–selenium (TOPSe). Both of the lead and chalcogenide precursors used in this method are inexpensive and air-stable, which largely reduces the cost of the reaction and simplifies the synthetic process. Five different shapes including quasi-spherical, cubic, octahedral, cuboctahedral and star shaped monodispersed PbSe nanocrystals were obtained, and the particle size can be easily tuned from ∼18 nm to ∼50 nm by varying the amount of oleic acid (OA) while keeping the amount of oleylamine (OLA) fixed. Oleic acid based growth orientation and shape evolution mechanism in double stabilizer surfactants was investigated in detail. The etching of PbSe nanocrystals was also observed when they were dispersed in toluene containing excessive amine over time, the etching process of oleylamine occurred on particle surfaces, and a new framework composed of nanorods formed around the nanocrystals. An ITO–PbSe–Al device based on a film of PbSe nanocrystals was constructed. The dark steadystate I–V characteristics of the films before and after ligand exchange revealed a broad prospect for the use of PbSe nanocrystals in light detection and infrared solar cells.