Mulder Jence T, Monchen Julius O V, Vogel Yan B, Lin Cheng Tai, Drago Filippo, Caselli Valentina M, Saikumar Niranjan, Savenije Tom J, Houtepen Arjan J
Optoelectronic Materials Section, Faculty of Applied Sciences, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands.
Chemistry Facility, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova, Italy.
J Am Chem Soc. 2024 Sep 4;146(35):24415-24425. doi: 10.1021/jacs.4c06340. Epub 2024 Aug 23.
Lead halide perovskites have attracted significant attention for their wide-ranging applications in optoelectronic devices. A ubiquitous element in these applications is that charging of the perovskite is involved, which can trigger electrochemical degradation reactions. Understanding the underlying factors governing these degradation processes is crucial for improving the stability of perovskite-based devices. For bulk semiconductors, the electrochemical decomposition potentials depend on the stabilization of atoms in the lattice-a parameter linked to the material's solubility. For perovskite nanocrystals (NCs), electrochemical surface reactions are strongly influenced by the binding equilibrium of passivating ligands. Here, we report a spectro-electrochemical study on CsPbBr NCs and bulk thin films in contact with various electrolytes, aimed at understanding the factors that control cathodic degradation. These measurements reveal that the cathodic decomposition of NCs is primarily determined by the solubility of surface ligands, with diminished cathodic degradation for NCs in high-polarity electrolyte solvents where ligand solubilities are lower. However, the solubility of the surface ligands and bulk lattice of NCs are orthogonal, such that no electrolyte could be identified where both the surface and bulk are stabilized against cathodic decomposition. This poses inherent challenges for electrochemical applications: (i) The electrochemical stability window of CsPbBr NCs is constrained by the reduction potential of dissolved Pb complexes, and (ii) cathodic decomposition occurs well before the conduction band can be populated with electrons. Our findings provide insights to enhance the electrochemical stability of perovskite thin films and NCs, emphasizing the importance of a combined selection of surface passivation and electrolyte.
卤化铅钙钛矿因其在光电器件中的广泛应用而备受关注。这些应用中一个普遍存在的因素是涉及钙钛矿的充电过程，这可能引发电化学降解反应。了解控制这些降解过程的潜在因素对于提高钙钛矿基器件的稳定性至关重要。对于体相半导体，电化学分解电位取决于晶格中原子的稳定性——这一参数与材料的溶解度相关。对于钙钛矿纳米晶体（NCs），电化学表面反应受到钝化配体结合平衡的强烈影响。在此，我们报告了一项针对与各种电解质接触的CsPbBr NCs和体相薄膜的光谱电化学研究，旨在了解控制阴极降解的因素。这些测量结果表明，NCs的阴极分解主要由表面配体的溶解度决定，在配体溶解度较低的高极性电解质溶剂中，NCs的阴极降解有所减少。然而，NCs的表面配体溶解度和体相晶格是相互独立的，因此找不到一种能使表面和体相都稳定以防止阴极分解的电解质。这给电化学应用带来了固有的挑战：（i）CsPbBr NCs的电化学稳定性窗口受溶解的Pb配合物还原电位的限制，（ii）在导带能够填充电子之前就会发生阴极分解。我们的研究结果为提高钙钛矿薄膜和NCs的电化学稳定性提供了见解，强调了综合选择表面钝化和电解质的重要性。
