Liquid metal embrittlement (LME) induced quasi-brittle fracture characteristics of a 9Cr-1Mo ferritic-martensitic steel (T91) after fatigue cracking in lead-bismuth eutectic (LBE) have been investigated at various length scales. The results show that the LME fracture morphology is primarily characterized by quasi-brittle translath flat regions partially covered by nanodimples, shallow secondary cracks propagating along the martensitic lath 2 boundaries as well as tear ridges covered by micro dimples. These diverse LME fracture features likely indicate a LME mechanism involving multiple physical processes, such as weakening induced interatomic decohesion at the crack tip and plastic shearing induced nano/micro voiding in the plastic zone.
2D Ruddlesden–Popper (RP)
perovskites have become emerging
photovoltaic materials due to their outstanding optoelectronic properties
and intrinsic structure stability. Here, two structurally similar
organic spacers with conjugated and unconjugated unites, namely FuMA
and THFMA, were developed to study their effects on the photophysical
properties of 2D RP perovskites. A very important finding is that
the 2D perovskite film (n = 4) based on FuMA with
a conjugated furan unit exhibits an ultralong average carrier lifetime
of 18.03 μs, which could be attributed to the enlarged dielectric
constant, reduced exciton binding energy, and decreased electron–phonon
coupling coefficients of the FuMA-based 2D RP perovskites. The optimized
device based on the FuMA spacer achieves a high PCE of 18.00% with
negligible hysteresis, much higher than that of the THFMA-based device
(PCE = 13.79%). This work opens a new avenue for developing 2D RP
perovskite films with ultralong carrier lifetimes for photovoltaic
and other optoelectronic applications.
2D Ruddlesden–Popper (2D RP) perovskite, with attractive environmental and structural stability, has shown great application in perovskite solar cells (PSCs). However, the relatively inferior photovoltaic efficiencies of 2D PSCs limit their further application. To address this issue, β‐fluorophenylethanamine (β‐FPEA) as a novel spacer cation is designed and employed to develop stable and efficient quasi‐2D RP PSCs. The strong dipole moment of the β‐FPEA enhances the interactions between the cations and [PbI6]4− octahedra, thus improving the charge dissociation of quasi‐2D RP perovskite. Additionally, the introduction of the β‐FPEA cation optimizes the energy level alignment, improves the crystallinity, stabilizes both the mixed phase and a‐FAPbI3 phase of the quasi‐2D RP perovskite film, prolongs the carrier diffusion length, increases the carrier lifetime and decreases the trap density. By incorporating the β‐FPEA, the quasi‐2D RP PSCs exhibit a power conversion efficiency (PCE) of 16.77% (vs phenylethylammonium (PEA)‐based quasi‐2D RP PSCs of 12.81%) on PEDOT:PSS substrate and achieve a champion PCE of 19.11% on the PTAA substrate. It is worth noting that the unencapsulated β‐FPEA‐based quasi‐2D RP PSCs exhibit considerably improved thermal and moisture stability. These findings provide an effective strategy for developing novel spacer cations for high‐performance 2D RP PSCs.
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