Minussi F B, Silva R M, Moraes J C S, Araújo E B
Department of Physics and Chemistry, São Paulo State University, Ilha Solteira, 15385-007, SP, Brazil.
Department of Electrical Engineering, São Paulo State University, Ilha Solteira, 15385-007, SP, Brazil.
Phys Chem Chem Phys. 2024 Aug 7;26(31):20770-20784. doi: 10.1039/d4cp02419b.
Halide perovskites are a class of materials of consolidated optoelectronic and electrochemical applications, reaching efficiencies compared to established materials in respective fields. In this scenario, the design and understanding of composition-structure-property relations is imperative. In solid solutions containing mixed cations, some direct relations between the sizes of the substituents and the properties of perovskites are generally observed. However, in several cases, these relations are not observed, implying that other characteristics of these cations play a major role. Despite its importance, this understanding has not been comprehensively deepened. To address this issue, we synthesized and characterized the structure, electrical behavior, and stability of methylammonium lead iodide-based perovskites with equal amounts of the substituents guanidinium, ethylammonium, and acetamidinium. These three large organic cations have essentially equal sizes but other remarkably different characteristics, such as the number of N-H bonds, intrinsic dipole moment, and order of C-N bonds. Herein, we show that these cations have dramatically different effects over important fundamental and applied properties of resulting perovskites, including the orthorhombic-to-tetragonal and tetragonal-to-cubic phase transitions, microstructural development, ionic conductivity, - hysteresis, electronic carrier mobility, and stability against light-induced degradation. These effects are correlated with the characteristics of the large substituent cations and help pave the way for a better rational chemical design of halide perovskites.
卤化物钙钛矿是一类在光电和电化学应用中已得到巩固的材料，在各自领域中与现有材料相比具有较高的效率。在这种情况下，对组成-结构-性能关系的设计和理解至关重要。在含有混合阳离子的固溶体中，通常会观察到取代基大小与钙钛矿性能之间的一些直接关系。然而，在某些情况下，并未观察到这些关系，这意味着这些阳离子的其他特性起着主要作用。尽管其很重要，但这种理解尚未得到全面深入。为了解决这个问题，我们合成并表征了含有等量取代基胍鎓、乙铵和脒鎓的甲基碘化铅基钙钛矿的结构、电学行为和稳定性。这三种大的有机阳离子大小基本相等，但具有其他显著不同的特性，例如N-H键的数量、固有偶极矩和C-N键的顺序。在此，我们表明这些阳离子对所得钙钛矿的重要基本性质和应用性质具有显著不同的影响，包括正交相到四方相以及四方相到立方相的转变、微观结构发展、离子电导率、滞后现象、电子载流子迁移率以及抗光致降解稳定性。这些影响与大取代基阳离子的特性相关，并有助于为卤化物钙钛矿更好的合理化学设计铺平道路。
