Studying Of The Photoluminescence Characteristics Of AgInS₂ Quantum Dots

The quantum dots are very potential materials in optical field. Now there are a lot of special properties of quantum dots and environmental non-toxic materials are paid more attention to people. Compared with the organic fluorescent dyes, quantum dots have the advantages of high fluorescence intensity, size controlled, long fluorescence lifetime. So from the beginning of the 1980s, the widespread concerns and interests are gained in study and great progress has been made in quantum dot materials.At present, quantum dots have wide applications in nano-biotechnology, nano-nergy technology, optoelectronics and environmental nanotechnology. The quantum dots obtain warm welcome in biological markers, light-emitting devices, solarcel, air purification and water treatment and other aspects.We choose suitable inorganic quantum dots in the experiment. The optical properties of AgInS₂ quant um dots（QDs）, which the average size is 5nm, are studied in detail. Through the testing experiment of AgInS₂ quantum dots, detailed understanding of photophysical characteristics of the excited state and the relaxation mechanism are studied. This paper includes researches on several related aspects of AgInS₂ quantum dots, the conclusions are as follows:As can be seen in the normalized PL spectra of AgInS 2 QDs in solution and aggregation state, the PL structure has only one PL peak with no fine structure. N oted their PL peaks red shift after AgInS₂ QDs aggregate together. The shifting of PL peak may be interpreted in terms of the self-absorption among AgInS₂ QDs after QDs aggregates together. The temperature dependent of PL spectra of AgInS 2 in solution and in aggregation state are detected. Apparently, the PL intensities of AgInS₂ QDs in solution and aggregation state could both decrease with the rising temperature. The photoluminescence（PL） of AgInS₂ QDs in solut ion and aggregation state exhib its an unusualte mperature-dependent peak shift behavior. The peak of AgInS₂ QDs in toluene solution is insensitive to the temperature. Meanwhile, the peak of AgInS₂ QDs in aggregation state is blue shifts as temperature increases.The excitation dynamics of AgInS₂ QDs in solution was scanned by using femtosecond transient absorption（TA） techniques, which allowed us to clarify the PL mechanism and relaxation process of excited AgInS₂ QDs in solution. We find that two kinds of emission-states（involving the exciton state and trapping state） participate in the PL process of QDs. The PL of exciton state and trapping state together participate in the whole PL process of AgInS₂ QDs in solution. So, the whole PL peak could be almost invariant as temperature inc reases. While, it is considered that the emission band of exciton state is bluer than that of trapping state, which could be suppressed by self-absorption in aggregation state. The who le PL peak of QDs could blue shift with temperature rising in aggregation state. The emission of trapping state is expected to play an important role in the temperature-dependent evolution of PL peak.