钙钛矿量子点因具有发光谱线窄、 发光效率高、 发光波长可调谐等优异的光学性能, 在照明、 显示、 激光和太阳能电池等领域得到了广泛研究。 然而, 钙钛矿材料的稳定性问题, 一直制约着其在光电器件中的应用。 其中, 钙钛矿材料在空气中受潮易分解的不稳定性尤为突出, 这将严重影响其发光性质。 为此, 研究人员采用多种手段来改善钙钛矿材料的稳定性。 目前, 常见的方法是将一些具有疏水性的聚合物材料（例如POSS, PMMA等）引入到钙钛矿纳米晶中, 或将钙钛矿纳米晶嵌入到介孔二氧化硅材料中, 避免钙钛矿纳米晶暴露于空气中破坏其结构, 以此来增强钙钛矿材料的发光稳定性。 此外, 钝化处理钙钛矿纳米晶表面, 也是改善钙钛矿发光稳定性的一种常用方法。 这些方法虽然在一定程度上可以改善钙钛矿的发光稳定性, 但是在与有机物合成的过程中不免会引入其他有机官能团, 介孔二氧化硅的引入, 其处理方式相对复杂, 而对钙钛矿纳米晶表面的钝化处理会破坏材料的原有结构。 以上问题, 都会影响钙钛矿的发光性质, 不利于其在光电器件中的应用。 硅（Si）具有低成本、 大尺寸、 高质量、 导电好等优点, 常被选作钙钛矿量子点光电器件的衬底材料。 但是, 由于Si衬底长时间暴露于空气, 其表面易形成一层具有硅烷醇基团（Si—OH）的亲水性薄膜, 这将对硅基钙钛矿器件的稳定性产生影响。 因此, 对Si表面进行钝化处理, 破坏其表面Si—OH键, 可以降低衬底表面的亲水性, 增强疏水性, 从而提高钙钛矿材料在器件中的稳定性。 本研究使用氢氟酸（HF）对Si衬底表面进行钝化处理, 发现钝化处理后的Si衬底表面与水的接触角由50.4°逐渐增大至87.7°, 表明Si衬底表面由亲水性逐渐转变为疏水性。 利用场致发射扫描电子显微镜(FE-SEM)测试发现, 钝化处理后的Si衬底表面变粗糙, 并且其表面上的CsPbBr3量子点(CsPbBr3 QDs)相对于未处理表面的分散性较好。 利用光致发光(PL)光谱研究不同钝化处理时间的Si衬底表面上的CsPbBr3 QDs薄膜的发光性质。 其中, 处理与未处理的Si衬底表面上CsPbBr3QDs薄膜的PL积分强度随功率变化拟合值分别为1.12和1.203, 表明其发光机制为激子发光。 温度依赖性的PL光谱分析显示, 随着温度的升高（10～300 K）, 由于晶格热膨胀使CsPbBr3 QDs带隙增大, 发光峰位逐渐蓝移。 并且, 随着衬底钝化处理时间的增加, CsPbBr3 QDs薄膜的发光热稳定性逐渐增强, 最佳热稳定性可达220 K。 而时间依赖性的PL光谱则进一步说明, 钝化处理后的Si衬底表面CsPbBr3QDs薄膜发光的时间稳定性逐渐增强, 最高发光时间稳定性可达15 d。 因此, 通过简单而有效的对Si衬底表面进行钝化处理, 可以有效减少了Si表面亲水基团, 提高CsPbBr3QDs薄膜的发光稳定性, 为增强钙钛矿量子点在光电器件中的稳定性应用提供了新的研究思路。

Perovskite quantum dots have been widely studied in the fields of illumination, display, and laser because of excellent luminescence properties, such as high luminous efficiency, narrow-band light emission, and adjustable optical wavelengths. However, the problem of stability of perovskite materials has prevented the application of perovskite photoelectric device. Among them, the perovskite material in the air is easy to decompose and the instability is particularly prominent, seriously affecting its luminescence properties. Therefore, the researchers have tried a variety of methods to improve the stability of perovskite materials. At present, the common way is to introduce some hydrophobic polymer materials (such as POSS, PMMA etc.) into the perovskite nanocrystals or embedded perovskite nanocrystals in mesoporous silica spheres to avoid the exposure of the perovskite nanocrystals to the air and the stability of perovskite material was enhanced effectively. Moreover, the surface of perovskite nanocrystals was passivated, and it was also a common method to improve the optical stability of perovskite. Although these methods can improve the optical stability of the perovskite nanocrystals, their preparation methods are complicated and will introduce other organic functional groups in the perovskite, and surface passivation treatment of perovskite nanocrystals can destroy the original structure of perovskite nanocrystals, which affects the optical properties of the perovskite nanocrystals, which is not conducive to their use in photovoltaic devices. For optical devices silicon (Si), it is a dominant material in today’s photoelectric device industry because of the low cost, large size, and good electrical conductivity. However, The Si has been exposed to the air for a long time, the surface layer is easily to form a hydrophilic silanol group (Si—OH), which will be detrimental to silicon-based perovskite devices stability. So, passivate the Si surface in order to destroy the surface hydrophilic groups (Si—OH) and make the surface from hydrophilic to hydrophobic, to improve the stability of perovskite material in the device. In this study, Use the hydrofluoric acid (HF) treatment for Si surface passivation. It was found that the contact angle of the Si substrate with water after passivation was changed from 50.4° to 87.7°, indicating that the surface of the silicon substrate was changed from hydrophilic to hydrophobic after HF passivation treatment. Field emission scanning electron microscope (FE-SEM) test showed that after the passivation of Si substrate surface is rough, CsPbBr3 QDs film are uniformly dispersed, which is different from the cluster of CsPbBr3 QDs film on the Si substrate surface which is not passivated. The optical properties of CsPbBr3 QDs film at different time were studied by photoluminescence (PL) spectroscopy, and the fitting results of the power-dependent PL measurement confirming the excitonic characteristics is exciton emission because β is 1.12 and 1.203. Through the temperature-dependent PL measurements, it was found that as the temperature rises, the peak energy will gradually have a blueshift because the thermal expansion of the lattice leads to the forbidden gap increases. When the temperature increased from 10 to 300 K, the thermal stability of CsPbBr3 QDs film increased gradually with the increase of passivation time to the Si substrate surface. And the time-dependent PL measurements showed, after HF passivation treatment Si substrate surface, the stability of the CsPbBr3 QDs film gradually increased and the luminescence stability was up to 15 days. Therefore, by simply and effectively passivating the bottom surface of the Si substrate, the hydrophilic groups on the surface can be effectively reduced, improving the Optica stability of the CsPbBr3 QDs film. This provides a new way to enhance the stability of CsPbBr3 QDs film in the application of optoelectronic devices.