TY - JOUR
T1 - Unraveling the influence of CsCl/MACl on the formation of nanotwins, stacking faults and cubic supercell structure in FA-based perovskite solar cells
AU - Pham, Huyen T.
AU - Yin, Yanting
AU - Andersson, Gunther
AU - Weber, Klaus J.
AU - Duong, The
AU - Wong-Leung, Jennifer
PY - 2021/9
Y1 - 2021/9
N2 - The incorporation of Cl anion and MA/Cs cations into FAPbI3 perovskite has been shown to dramatically improve solar cell performance. However, the microscopic properties of hybrid metal halide perovskite materials are not well understood yet, and it is still unclear how ion incorporation stabilizes the cubic FAPbI3 perovskite. In this work, we conduct a systematic study on the effect of the CsCl/MACl additives on the microstructure, crystal structure, and defects (nanotwins and stacking faults) of FA-based perovskite solar cells (PSCs). We find that the cubic α-phase in pure FAPbI3 is unstable with evidence of additional phases in the experimental electron diffraction analyses, namely the hexagonal δ-phase, the cubic supercell structure (with double the lattice constant of the α-phase) and a rhombohedral phase. The addition of CsCl/MACl effectively stabilizes the cubic FAPbI3 with a 2 × 2 × 2 supercell expansion and the Im3̅ space group. X-ray diffraction and photoluminescence studies show that the addition of CsCl/MACl results in a change in both the lattice parameter and the optical bandgap, respectively. The lattice contraction is a result of the incorporation of Cs/MA cations and Cl anion in the FAPbI3 perovskites. Moreover, the addition of CsCl is shown to minimize the density of defects and improve the photoluminescence yield as well as the minority carrier lifetime of the perovskite films. All of these factors contribute to the improved device performance with a maximum efficiency of 21.98% measured for the 10 mol% CsCl perovskite layer.
AB - The incorporation of Cl anion and MA/Cs cations into FAPbI3 perovskite has been shown to dramatically improve solar cell performance. However, the microscopic properties of hybrid metal halide perovskite materials are not well understood yet, and it is still unclear how ion incorporation stabilizes the cubic FAPbI3 perovskite. In this work, we conduct a systematic study on the effect of the CsCl/MACl additives on the microstructure, crystal structure, and defects (nanotwins and stacking faults) of FA-based perovskite solar cells (PSCs). We find that the cubic α-phase in pure FAPbI3 is unstable with evidence of additional phases in the experimental electron diffraction analyses, namely the hexagonal δ-phase, the cubic supercell structure (with double the lattice constant of the α-phase) and a rhombohedral phase. The addition of CsCl/MACl effectively stabilizes the cubic FAPbI3 with a 2 × 2 × 2 supercell expansion and the Im3̅ space group. X-ray diffraction and photoluminescence studies show that the addition of CsCl/MACl results in a change in both the lattice parameter and the optical bandgap, respectively. The lattice contraction is a result of the incorporation of Cs/MA cations and Cl anion in the FAPbI3 perovskites. Moreover, the addition of CsCl is shown to minimize the density of defects and improve the photoluminescence yield as well as the minority carrier lifetime of the perovskite films. All of these factors contribute to the improved device performance with a maximum efficiency of 21.98% measured for the 10 mol% CsCl perovskite layer.
KW - Crystal structure
KW - Microstructure
KW - Nanotwins
KW - Perovskite
KW - Stacking faults
KW - TEM
UR - http://www.scopus.com/inward/record.url?scp=85108207530&partnerID=8YFLogxK
U2 - 10.1016/j.nanoen.2021.106226
DO - 10.1016/j.nanoen.2021.106226
M3 - Article
AN - SCOPUS:85108207530
VL - 87
JO - Nano Energy
JF - Nano Energy
SN - 2211-2855
M1 - 106226
ER -