@phdthesis{oai:oist.repo.nii.ac.jp:00002182,
 author = {Jamshaid, Afshan},
 month = {2022-06-01, 2021-08-13},
 note = {This thesis discusses the understanding of the structural and electronic properties 
of metal halide perovskite materials (e.g., CH3NH3PbI3) as well as the interaction with 
additive materials at the atomic scale. Metal halide perovskite materials are currently at 
the core of attention because of their high-efficiency attainable when utilized in solar cell 
applications as well as lost fabrication cost. However, the stability of these perovskite 
materials and perovskite-based solar cells is still a major challenge. The proposed 
atomic-scale research helps address the thermal instability and ambient air induced 
degradation issues commonly observed in perovskites. Incorporation of additive 
materials into the perovskite was reported to be an efficient strategy to enhance the 
stability. Cl and KI have been found to be eligible candidates but studies on the 
fundamental processes at the atomic scale of these additives are scarce. Therefore, we 
comprehensively investigated Cl incorporation in MAPbI3 at the atomic scale by 
combining scanning tunneling microscopy (STM), X-ray photoelectron, ultraviolet, and 
inverse photoemission spectroscopy. For the Cl concentration of 14.8 ± 0.6%, STM 
images confirm the presence of Cl ions on the MAPbI3 (MAPbI2.59Cl0.21) surface leading 
to the highest surface stability found from the viewpoint of both thermodynamics and 
kinetics by density functional theory and molecular dynamics calculations. This study 
evidence that Cl can substitute I ions of the surface structure and/or fill the surface I-
vacancies and further enhance the structural stability of MAPbI3. Upon the PbCl2
deposition on MAPbI3, only Cl ions were observed in MAPbI3 surface crystal structure 
while Pb ions were not observed by LT-STM. Before investigating the PbCl2 interaction 
with MAPbI3, the atomic structures of metallic-Pb and PbCl2 on Au (111) substrate need 
be studied by LT-STM. For the PbCl2/Au (111) system, a myriad of structures such as 
the intact form of PbCl2 as well as dissociated species in the forms of Cl ions, Cl-Cl 
dimer, Pb, and Pb-Pb dimers were observed. Furthermore, the KI additive was 
investigated by LT-STM, which reveals the I-I square atomic structure. After deposition 
protocol optimization, KI was deposited on MAPbI3 and characterized by XPS 
confirming K incorporation in MAPbI3. As a future plan, LT-STM studies can be 
conducted to find the optimal concentration of KI for enhancing the MAPbI3 surface 
stability. Also, it is important to point out that STM can be used to characterize mainly 
the surface atomic structures of perovskite materials.},
 school = {Okinawa Institute of Science and Technology Graduate University},
 title = {走査型プローブ顕微鏡を用いた金属ハロゲン化物ペロブスカイト型材料の研究},
 year = {}
}