离子交换树脂改性的CsPbBr_(3)量子点特性研究

Research on the Properties of CsPbBr_(3) Quantum Dots Modified by Ion Exchange Resin

全无机钙钛矿量子点(PQDs)对环境的不稳定性问题成为了制约其实际应用的潜在威胁,从PQDs材料本身出发研究相应的性能和稳定性提升方案意义重大。本文通过引入离子交换树脂的缺陷钝化和选择性去除作用,实现了同时对CsPbBr_(3) PQDs性能改善和稳定性提升。一方面,引入离子交换树脂可以在不改变PQDs固有晶相的情况下选择性地去除形貌差、结构不稳定的PQDs单晶,这使得所制备的PQDs的表面形貌和均一性得到了很大程度的改善,并且在长时间紫外光照和高温实验下,PQDs的稳定性也得到较大提升;另一方面,在改性前后,CsPbBr_(3) PQDs的光致发光量子产率(PLQY)和荧光寿命都有了显著提升,PLQY从53.23%提高到了90.00%,荧光寿命则从10.4 ns提高到了22.2 ns。本文研究为PQDs的性能改善与稳定性提升提供了新的思路,由于离子交换树脂可再生和低成本的特性,在光电领域具有广阔的应用前景。

All-inorganic perovskite quantum dots have attracted much attention because of their outstanding photoelectric properties.However,the instability of PQDs to the environment has become a potential threat that restricts its practical application.At present,a large number of scientific studies have been devoted to improving the stability of PQDs.However,most of the current stability improvement schemes are to encapsulate PQDs in hydrophobic materials to provide a physical barrier against environmental changes,while the defects and unstable performance of materials themselves have not been effectively improved.It is therefore of great significance to study the corresponding performance and stability improvement schemes from the PQDs material itself.Ion exchange resin is a kind of polymer compound with a functional group,a network structure and insolubility.As for anion exchange resin,its active group can adsorb different types of anions to achieve ion exchange reaction,while PQDs is a kind of ionic compound containing halogen anions,and the two have a good binding ability.In this study,the performance and stability of CsPbBr_(3) PQDs were improved simultaneously by introducing defect passivation and selective removal of ion exchange resin.The product PQDs prepared by high temperature thermal injection method was named as the original sample,and the sample treated with Br type anion exchange resin was named as the modified sample.From direct observation of their appearance,the original sample is yellow-brown,while the modified sample after ion exchange resin treatment is transparent green.The resean is the large number of micropores in the ion exchange resin,which has strong an adsorption capacity comparable to activated carbon,and can selectively adsorb and remove organic impurities.TEM images show that the original sample has poor surface morphology.In contrast,the modified samples treated with ion-exchange resin show clear cubic phase with almost no surface damage or structural distortion.It is worth mentioning that continuous UV excitation and high temperature environment will lead to partial crystal phase separation of PQDs,and the surface ligand will fall off,resulting in grain agglomeration and decreased fluorescence intensity.The luminescence intensity of the original sample and the modified sample decreases to 80.6%and 85.7%respectively after 3 h of UV excitation,and to 75.2%and 99.6%respectively after 2 hours of 70℃heating.Obviously,the fluorescence intensity attenuation of the modified sample is relatively less,showing more excellent stability.It is worth noting that after high temperature heating,the fluorescence intensity of the modified sample almost does not decay,showing excellent thermal stability.Compared with the original sample,the modified sample also had a longer average fluorescence lifetime.The third-order exponential decay model was used to fit the fluorescence lifetime curve,and the results show that the average fluorescence lifetime of the original sample and the modified sample was 10.4 ns and 22.2 ns,respectively.The defects in the crystal will act as the center of non-radiation recombination to inhibit the radiation recombination process,and the increase of the final average fluorescence life indicates that the radiation recombination is enhanced,which also reflects the reduction of defect states from the side.The improvement of average fluorescence lifetime indicates that the excess halogen anions released by anion exchange resin contribute largely to the passivation of surface defects and the improvement of optical properties of PQDs.The PLQY of the original sample and the modified sample were 53.23%and 90.00%,respectively.Such a large increase in PLQY is not only due to the direct band gap characteristics of the material itself,which can improve the light absorption coefficient and speed up the radiation recombination rate,but also due to the passivation of excessive halogen anions on the surface defects of quantum dots,thus reducing a large number of non-radiation recombination paths.In summary,the introduction of ion exchange resin can selectively remove PQDs single crystals with poor morphology and unstable structure without changing the inherent crystal phase of PQDs,which makes the surface morphology and uniformity of the prepared PQDs greatly improved.And the stability of PQDs has also been greatly improved under long-term ultraviolet light and high temperature experiments.Moreover,before and after modification,the photoluminescence quantum yield and fluorescence lifetime of CsPbBr_(3) PQDs were significantly increased from 53.23%to 90.00%and from 10.4 ns to 22.2 ns,respectively.This research provides a new idea for improving the performance and stability of PQDs.Due to the reproducible and low-cost characteristics of ion exchange resins,it has broad application prospects in the field of optoelectronics.