| dc.description.abstract | Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIP) possess high chemical stability, low production cost, and great optoelectronic and semiconductor properties, which permit great potential in widespread applications such as solar cells,
light-emitting diodes, flexible devices, and triboelectric nanogenerators (TENGs). During these applications, 2D HOIPs would slide against each other or other interfacing materials causing damage or changes to the structure of HOIPs during service. Understanding the frictional properties of 2D HOIPs is thus vital for the durability and performance of these devices. However, little is known about the frictional behaviors of 2D HOIPs. The main objectives of this work are to shed light on the effect of organic ligands and humidity on
the friction behavior of HOIPs. In this work, Friction coefficients of the two most commonly used single-crystalline HOIPs, butylammonium lead iodide ((BA)2PbI4 (C4n1)) and phenylethyl ammonium lead iodide ((PEA)2PbI4 (PEAn1)), are measured under different humidity conditions using Friction force microscopy with a diamond-coated probe. The COF of PEAn1 is found always lower than that of C4n1 in both ambient and dry environments, probably due to the higher hardness of PEAn1 and the steric hindrance of the phenyl terminal group preventing direct interaction of the tip with underlying methylene groups. The humidity shows different effects on the COFs of the AFM tip sliding on the two HOIP crystal surfaces. The difference might be related to the hydrophobicity of the
spacer molecules, the moisture-induced packing of the organic ligands on the surfaces, and the non-monotonic dependence of COF on the amount of water molecules at the tip-iii
sample interface. The thesis concludes with a discussion on future research directions related to the frictional properties of 2D HOIPs. | en |
