Luo Yi - KTH

Serial electron diffraction (SerialED), which applies a snapshot data acquisition strategy for each crystal, was introduced to tackle the problem of radiation damage in the structure determination of beam-sensitive materials by three-dimensional electron diffraction (3DED). The snapshot data acquisition in SerialED can be realized using both transmission and scanning transmission electron microscopes (TEM/STEM). However, the current SerialED workflow based on STEM setups requires special external devices and software, which limits broader adoption. Here, we present a simplified experimental implementation of STEM-based SerialED on Thermo Fisher Scientific STEMs using common proprietary software interfaced through Python scripts to automate data collection. Specifically, we utilize TEM Imaging and Analysis (TIA) scripting and TEM scripting to access the STEM functionalities of the microscope, and …

Wide-bandgap (> 1.7 eV) perovskites suffer from severe light-induced phase segregation due to high bromine content, causing irreversible damage to device stability. However, the strategies of suppressing photoinduced phase segregation and related mechanisms have not been fully disclosed. Here, we report a new passivation agent 4-aminotetrahydrothiopyran hydrochloride (4-ATpHCl) with multifunctional groups for the interface treatment of a 1.77-eV wide-bandgap perovskite film. 4-ATpH+ impeded halogen ion migration by anchoring on the perovskite surface, leading to the inhibition of phase segregation and thus the passivation of defects, which is ascribed to the interaction of 4-ATpH+ with perovskite and the formation of low-dimensional perovskites. Finally, the champion device achieved an efficiency of 19.32% with an open-circuit voltage (VOC) of 1.314 V and a fill factor of 83.32%. Moreover, 4-ATpHCl …

Severe open-circuit voltage (VOC) loss significantly hinders the performance improvement of wide-bandgap (WBG) perovskite solar cells (PSCs) and their application in perovskite-based tandem devices. Herein, we develop a novel self-assembled monolayer of (4-(5,9-dibromo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (DCB-BPA) as the hole-selective layer for WBG PSCs with a 1.77 eV perovskite absorber. DCB-BPA facilitates the subsequent growth of WBG perovskite with improved buried-interface quality. Compared with that of poly(triarylamine) PTAA-based control devices, a substantially enhanced average VOC from 1.18 V to 1.31 V of DCB-BPA-based devices has been realized due to reduced interfacial nonradiative recombination and enhanced energy level alignment. Our certified device delivers an impressive VOC of up to 1.339 V and a power conversion efficiency (PCE) of 18.88 …

Living on Mars requires the ability to synthesize chemicals that are essential for survival, such as oxygen, from local Martian resources. However, this is a challenging task. Here we demonstrate a robotic artificial-intelligence chemist for automated synthesis and intelligent optimization of catalysts for the oxygen evolution reaction from Martian meteorites. The entire process, including Martian ore pretreatment, catalyst synthesis, characterization, testing and, most importantly, the search for the optimal catalyst formula, is performed without human intervention. Using a machine-learning model derived from both first-principles data and experimental measurements, this method automatically and rapidly identifies the optimal catalyst formula from more than three million possible compositions. The synthesized catalyst operates at a current density of 10 mA cm−2 for over 550,000 s of operation with an overpotential of …

Understanding the atomic scale structural dynamics of phase transformations is crucial for developing new materials and tailoring the properties of the materials. However, many materials are obtained as polycrystalline powders with large unit cells and/or complex structures, making it challenging to investigate detailed structural changes using conventional X-ray diffraction techniques. Here, we employ time-resolved 3D electron diffraction (3D ED) to unravel the topotactic reactions and transformations of extra-large pore silicate zeolites ECNU-45 to ECNU-46. Notably, ECNU-45 features 3D interconnecting 24×10×10-ring channels, while ECNU-46 exhibits 1D 24-ring channels connected to 10-ring pockets. ECNU-45 and ECNU-46 are the first reported examples of pure silicate zeolites with pores larger than 22-rings. Our findings showcase detailed changes at six distinct tetrahedral Si sites, involving atom displacement, addition, and removal of framework atoms through bond breakage and formation. This work not only presents the discovery of novel zeolites but also provides unprecedented atomic-level insights into the dynamic processes of topotactic reactions. Our results have significant implications for advancing materials engineering and understanding complex solid-state reactions at an atomic scale.

Vibrational coherence has attracted considerable research interests because of its potential functions in light harvesting systems. Although positive signs of vibrational coherence in metal nanoclusters have been observed, the underlying mechanism remains to be verified. Here, we demonstrate that robust vibrational coherence with a lifetime of 1 ps can be clearly identified in Ag44(SR)30 core–shell nanoclusters, in which an icosahedral Ag12 core is well protected by a dodecahedral Ag20 cage. Ultrafast spectroscopy reveals that two vibrational modes at around 2.4 THz and 1.6 THz, corresponding to the breathing mode and quadrupolar-like mode of the icosahedral Ag12 core, respectively, are responsible for the generation of vibrational coherence. In addition, the vibrational coherence of Ag44 has an additional high frequency mode (2.4 THz) when compared with that of Ag29, in which there is only one low …

Raman spectroscopy is a versatile tool for acquiring molecular structure information. The incorporation of plasmonic fields has significantly enhanced the sensitivity and resolution of surface-enhanced Raman scattering (SERS) and tip-enhanced Raman spectroscopy (TERS). The strong spatial confinement effect of plasmonic fields has challenged the conventional Raman theory, in which a plane wave approximation for the light has been adopted. In this review, we comprehensively survey the progress of a generalized theory for SERS and TERS in the framework of effective field Hamiltonian (EFH). With this approach, all characteristics of localized plasmonic fields can be well taken into account. By employing EFH, quantitative simulations at the first-principles level for state-of-the-art experimental observations have been achieved, revealing the underlying intrinsic physics in the measurements. The predictive …

All-perovskite tandem solar cells (TSCs) have exhibited higher efficiencies than single-junction perovskite solar cells (PSCs) but still suffer from the unsatisfactory performance of low-bandgap (LBG) tin-lead (Sn-Pb) subcells. The inherent properties of PEDOT:PSS are crucial to high-performance Sn-Pb perovskite films and devices; however, the underlying mechanism has not been fully explored and revealed. Here, we report a facile oxalic acid treatment of PEDOT:PSS (OA-PEDOT:PSS) to precisely regulate its work function and surface morphology. OA-PEDOT:PSS shows a larger work function and an ordered reorientation and fiber-shaped film morphology with efficient hole transport pathways, leading to the formation of more ideal hole-selective contact with Sn-Pb perovskite for suppressing interfacial nonradiative recombination losses. Moreover, OA-PEDOT:PSS induces (100) preferred orientation growth of …