Sahoo Kajol, Juneja Latika, Naik Ramakanta, Bhaumik Saikat
Department of Engineering and Materials Physics, Institute of Chemical Technology IndianOil Odisha Campus Bhubaneswar Odisha 751013 India.
Department of Physics, Indian Institute of Technology Guwahati Assam 781039 India
Nanoscale Adv. 2025 Jul 14. doi: 10.1039/d5na00412h.
In recent years, metal halide perovskite nanocrystals (NCs) have offered several optoelectronic and sensing applications due to their unique photophysical properties. Formamidinium (FA) based perovskite NCs exhibit better thermal and structural stability than the corresponding volatile methylammonium (MA)-based counterpart, which quickly decomposes to release gaseous methylamine. FA-based perovskite NCs also demonstrate fantastic responses towards different environmental stimuli, which is helpful for different sensing applications. However, FAPbI NCs suffer from phase instability and degrade very fast under external stimuli. Here, we synthesized mixed halide FAPb(Br/I) NCs by partially replacing I-ions with Br-ions to address the key challenge of phase instability of FAPbI NCs. Furthermore, with a surface modification approach such as encapsulating the surface of NCs with silica and also a double-encapsulated silica-polymethyl methacrylate (PMMA) polymer, we enhanced the stability of the NCs against heat, ion migration, and UV irradiation. These double-coated red-emitting FAPb(Br/I) NCs (emission peak ∼ 642 nm) were tested for temperature sensing, exhibiting a relative sensitivity ( ) of ∼12.5% K. We also prepared fluorescent humidity sensors that revealed the lowest detection limit of ∼5% relative humidity (RH). Finally, down-converted WLEDs were fabricated using double-coated green-emitting Cs-doped FAPbBr NCs and red-emitting FAPb(B/I) NCs in thin-film form and embedded on a blue LED chip. These results will boost the development of high-performance sensors and lighting technologies.
近年来，金属卤化物钙钛矿纳米晶体（NCs）因其独特的光物理性质而在多种光电子和传感应用中得到应用。基于甲脒（FA）的钙钛矿NCs比相应的基于挥发性甲胺（MA）的同类产品表现出更好的热稳定性和结构稳定性，后者会迅速分解以释放气态甲胺。基于FA的钙钛矿NCs对不同的环境刺激也表现出出色的响应，这有助于不同的传感应用。然而，FAPbI NCs存在相不稳定问题，在外部刺激下降解非常快。在此，我们通过用Br-离子部分取代I-离子来合成混合卤化物FAPb(Br/I) NCs，以解决FAPbI NCs相不稳定的关键挑战。此外，通过表面改性方法，如用二氧化硅封装NCs表面以及采用二氧化硅-聚甲基丙烯酸甲酯（PMMA）聚合物双封装，我们提高了NCs对热、离子迁移和紫外线照射的稳定性。这些双包覆的发红光FAPb(Br/I) NCs（发射峰约为642 nm）用于温度传感测试，相对灵敏度约为12.5% K。我们还制备了荧光湿度传感器，其显示出约5%相对湿度（RH）的最低检测限。最后，使用双包覆的薄膜形式的绿色发光Cs掺杂FAPbBr NCs和红色发光FAPb(B/I) NCs制备了下转换白光发光二极管（WLEDs），并将其嵌入蓝色LED芯片上。这些结果将推动高性能传感器和照明技术的发展。
