Properties Of Composite Thin Films Based On Mn Doped ZnSe Semiconductor Nanocrystals

Semiconductor nanocrystals are generally called to be quantum dots. Quantum dots have attracted significant research interest over the past few decades in the fields from light-emitting diodes(LEDs), biomarker to luminescent solar concentrators which is due to its unique optical properties. This paper is mainly focused on physical properties of composite thin films based on Mn doped ZnSe quantum dots.Initially, quantum dots are directly used in synthesis of composite thin films. However, quantum dots do not get ideal optical properties because of fluorescence performance reducing obviously due to the negative impact of the complex environment on quantum dots in the process of polymerization. In order to solve this problem, hot injection strategy was used to synthesize Mn doped ZnSe quantum dots in high boiling point solvents first, and then two ways of treatments were used to treat them before they were dispersed in organic polymer monomer, which were prepared into composite thin films finally.One is using dodecanethiol to treat Mn doped ZnSe quantum dots in the later sta ge of preparation. Then the quantum dots were used to synthesize composite thin films. The quantum yield of Mn doped ZnSe quantum dots increased from 61.5% to 75.6% with an enhancement of 14.1% after treated with 1 mL of dodecanethiol while the quantum yield of composite thin films increased from 35.4% to 67.1%, with an enhancement of 31.7%. These performances show that it not only enhanced the quantum yield of quantum dots but also protected quantum dots from the negative impact of environment in the process of synthesizing composite thin films. This treatment will not change the position of emission and absorption peak at the same time, which is suitable for the scheme having special request for spectral wavelength.The other one is injecting S precursor and Zn precursor respectively in the later stage of synthesis, which result in coating ZnS outside of Mn doped Zn Se quantum dots, and then treated with dodecanethiol. Then the quantum dots were used to synthesize composite thin films. In such way, ZnS protected Mn doped ZnSe inside in the process of polymerization. The quantum yield of composite thin film increased 8.7% more than that of the former. However, this strategy will increase the size of quantum dots along with emission peak emerging red-shift. It is more suitable for the scheme which has higher requirements of quantum yield.The average transmittances of composite thin films synthesized by the quantum dots after treatments are higher than 90% in the range from 500 nm to 800 nm,which is higher than that of composite thin films, showing average transmittances with 88%, synthesized by the quantum dots not treated.