Synthesis Of Cdse Nanocrystals By Organic Solvent And Modified With Surfactant

Semiconductor nano-material is considered to be the most anticipated solar cell material because of its unique optical and chemical properties, which caused by its quantum size effect, surface effect and the photoelectric effect. Considerable attention has been given to CdSe nano-materials whose band gap width is very close to the photovoltaic cells required for optimal parameters.N-methyl pyrrolidone (NMP) was used as synthetic organic solvent, cadmium nitrate and sodium selenite as cadmium and selenium source, ammonia as complexing agent and hydrazine hydrate as reducing agent. There are two kinds of precursor injection: hot injection and room temperature injection. Various parameters were investigated, such as complexing agent, refluxing temperature, refluxing time ,and so on. Surfactant was used in the synthesis process to modify nanocrystallin. Then nanocrystalline thin film was prepared.In the hot injection, zinc-blende CdSe nanocrystals were synthesized by ammonia complex cadmium nitrate and wurtzite structure synthesized by citric acid complex. When we used ammonia as the complex agent, the best refluxing temperature is 180℃The size of the nanocrystals changed little when Cd/Se changed, but the nanocrystals phase changed. The pure zinc-blende CdSe was obtained when Cd / Se = 1:1. And the size of nanocrystal mainly distributed in 10 ~ 13nm. FT-IR analysis demonstrated that NMP molecules had coordinating characteristic. UV-Vis absorption analysis showed that the band gap of zinc-blende CdSe nanocrystalline was 1.82eV.Wurtzite-Type CdSe was synthesized by room temperature injection. With the increasing of refluxing time, the size of nanocrystals increased. And the best refluxing time is 30min. With the increasing of refluxing temperature, agglomeration appeared. The best refluxing temperature is 180 degree. The range of the largest size distribution of nano-crystalline was 11nm to 12nm. UV–Vis absorption analysis demonstrated that the band gap of wurtzite-type nanocrystals was 1.76eV.The morphology of particles did not change when Surfactant polyvinyl pyrrolidone (PVP) was added. But with its help, the nanocrystalline thin film was prepared. There was little impact when we added Polyethylene glycol (PEG). Nanoclusters were synthesized when cetyltrimethylammonium bromide (CTAB) was added.