Growth and properties of solvothermally derived CZTSe nanocrystals using elemental precursors

Cu2ZnSnSe4 (CZTSe) nanocrystals were prepared by a solvo-thermal method using elemental copper, zinc, tin and selenium powders as precursors and ethylenediamine as a stabilizer and chelating medium. The particles were synthesized at 180 °C after which they were annealed at 300 °C and 400 °C for 1 h. The influence of annealing the nanocrystals, on the crystal structure, particle size, morphology, composition and optical properties has been investigated. As-grown particles were found to contain secondary phases, which subsequently transformed into CZTSe nanocrystals upon annealing. XRD and Raman results confirmed that the samples recrystallized into kesterite CZTSe on annealing at 400 °C. SEM studies show that the as-grown material has a platelet like morphology, and after annealing at 400 °C, freshly formed nanosized particles (10-20 nm) appear. TEM studies reveal that the grain size of CZTSe nanoparticles is about 5-10 nm. Optical studies show that the band gap energy exhibits a blue shift in the range 1.3-1.6 eV, indicative of quantum confinement of electrons.