Sen Arghya, Dutta Abhijit, Bose Abir Lal, Sen Pratik
Department of Chemistry, Indian Institute of Technology Kanpur Kanpur - 208 016 UP India
Department of Chemical Engineering, Indian Institute of Technology Kanpur Kanpur - 208 016 UP India.
Chem Sci. 2024 Nov 26;16(2):735-752. doi: 10.1039/d4sc05565a. eCollection 2025 Jan 2.
Quantum-confined, two-dimensional (2D) CsPbBr (CPB) nanoplates (NPLs) have emerged as exceptional candidates for next-generation blue LEDs and display technology applications. However, their large surface-to-volume ratio and detrimental bromide vacancies adversely affect their photoluminescence quantum yield (PLQY). Additionally, external perturbations such as heat, light exposure, moisture, oxygen, and solvent polarity accelerate their transformation into three-dimensional (3D), green-emitting CPB nanocrystals (NCs), thereby resulting in the loss of their quantum confinement. Until now, no reported strategies have successfully addressed all these issues simultaneously. In this study, for the first time, we prepared oleylammonium fluoride (OAmF) salt and applied it post-synthetically to CPB NPLs with thicknesses of = 3 and = 4. Steady state and time-resolved photoluminescence (TRPL) measurements like fluorescence upconversion and TCSPC confirmed the elimination of detrimental deep trap states by fluoride ions, resulting in an unprecedented improvement in PLQY to 85% for = 3 and 98% for = 4. Furthermore, the formation of robust Pb-F bonds, coupled with strong electrostatic and hydrogen-bonding interactions, resulted in a highly stable NPL surface-ligand interaction. This concrete surface architecture restricts the undesired phase transition of 2D NPLs into 3D NCs under various external perturbations, including heat up to 363 K, strong UV irradiation, water, atmospheric conditions, and solvent polarity. Also, the temperature dependent TRPL measurements provide an insight into the charge carrier dynamics under thermal stress conditions and reveal the location of shallow trap states, which lie below 7 meV from the conduction band edge. In brief, our innovative OAmF salt has effectively addressed all the critical issues of 2D CPB NPLs, paving the way for next-generation LED applications. This breakthrough not only enhances the stability and PLQY of CPB NPLs but also offers a scalable solution for the advancement of perovskite-based technologies.
量子限域的二维（2D）CsPbBr（CPB）纳米片（NPLs）已成为下一代蓝色发光二极管和显示技术应用的优异候选材料。然而，它们较大的表面积与体积比以及有害的溴化物空位对其光致发光量子产率（PLQY）产生了不利影响。此外，诸如热、光照、湿度、氧气和溶剂极性等外部干扰会加速它们转变为三维（3D）、发射绿色光的CPB纳米晶体（NCs），从而导致其量子限域的丧失。到目前为止，尚无已报道的策略能同时成功解决所有这些问题。在本研究中，我们首次制备了油基氟化铵（OAmF）盐，并在合成后将其应用于厚度为 = 3和 = 4的CPB NPLs。诸如荧光上转换和时间相关单光子计数（TCSPC）等稳态和时间分辨光致发光（TRPL）测量证实氟离子消除了有害的深陷阱态，使得 = 3时PLQY前所未有的提高到85%， = 4时提高到98%。此外，坚固的Pb - F键的形成，再加上强烈的静电和氢键相互作用，导致了高度稳定的NPL表面 - 配体相互作用。这种具体的表面结构限制了2D NPLs在各种外部干扰下，包括高达363 K的热、强紫外辐射、水、大气条件和溶剂极性下转变为3D NCs的不期望的相变。而且，温度相关的TRPL测量提供了对热应力条件下电荷载流子动力学的深入了解，并揭示了浅陷阱态的位置，其位于导带边缘以下7 meV处。简而言之，我们创新的OAmF盐有效地解决了2D CPB NPLs的所有关键问题，为下一代LED应用铺平了道路。这一突破不仅提高了CPB NPLs的稳定性和PLQY，还为基于钙钛矿的技术进步提供了一种可扩展的解决方案。
