Atsushi Wakamiya

Coordinated control of oxidation, composition, crystallization, surface defects, and charge-transport layers is essential for advancing tin perovskite solar cells toward efficient, stable, and scalable devices.

Circularly polarized (CP) terahertz (THz) fields are promising for controlling angular momentum in solids. While resonator structures can be used to enhance THz electric fields, a highly localized enhancement makes it difficult to accurately characterize the amplitude and polarization of the local near-field maximum using thick electro-optic crystals. We demonstrate a local probing method based on a band edge modulation in methylammonium lead iodide (MAPbI3) perovskite thin films. The THz-induced transmittance change, ΔT, in the near-infrared (as well as the reflectance change, ΔR) can be used to determine the near-field amplitude, while the degree of the modulation of ΔT (or ΔR) due to the oscillating THz electric-field vector yields the ellipticity ε. The extracted ellipticity is close to the ideal value (within ±0.05) for ε > 0.4. A comparison with finite-difference time-domain simulations shows that this method can be used to characterize the amplitude and ellipticity of the enhanced CP field in the gap of a crosshair resonator with good accuracy. The simulations also reproduce the experimentally observed long-lived near-field waveform well and indicate that the observed difference between the theoretical and experimental ε mainly arises from a probe spot that is slightly displaced from the gap center by about 1 μm. Since this resonator structure has an enhancement factor of 11.8 ± 0.3 and a high preservation of circularity, the combination of this resonator with the proposed probing method should be useful for studies using strong THz fields.

Many nanoscale materials, ranging from environmental particulates to carrier‐free nanomedicine platforms, enter the human body, yet their metabolic fates remain poorly understood. This process involves complex physical changes and molecular transformations within lysosomes; however, the particle‐to‐molecule transition–defined here as “nanometabolism”–has remained difficult to quantify due to intrinsic limitations of nanoscale bioimaging. To circumvent the fluorescence quenching of conventional fluorophores and the challenges of observing nanoscale dynamics, peak‐shifted, dual‐state emissive nanoprobes composed entirely of donor–acceptor bithiophene dyes are introduced here. This approach establishes a highly adaptable design strategy for constructing heterogeneous organic nanoparticles templated by these molecular metrics. These molecular probes generate bright, ratiometric spectral shifts that directly encode nanoparticle disassembly, enabling robust optical monitoring of intracellular nanometabolism with cell‐type‐ and particle‐size‐resolution. Time‐resolved imaging identifies protonation‐induced lysosomal membrane destabilization as the primary driver of nanoparticle breakdown within 6–12 h. Supported by cryogenic correlative imaging and tissue‐level tracking, this platform provides a promising optical framework for monitoring nanometabolism in living systems. It serves as a pivotal breakthrough in elucidating the mechanistic design rules required for the future development of carrier‐free nanomedicines with predictable intracellular behavior.

The development of a new building block for creating solution‐processable amorphous n‐type semiconductors provides a platform of fundamental importance for advanced organic electronic materials. We have recently demonstrated that oxidative inner‑bond cleavage of readily available dibenzo[ g , p ]chrysene affords a chiral figure‑eight macrocycle that bears electron‑withdrawing carbonyl groups, namely cyclobisbiphenylenecarbonyl (CBBC). In this study, we report a highly electron‑accepting derivative of CBBC (CBBC‑TIC), in which the CBBC core is connected to four electron‑withdrawing dicyanomethylene‑3‑indanone (IC) units via thiophene spacers. The distinctive X‑shaped molecular structure of CBBC‑TIC enables the solution‐process fabrication of a homogeneous amorphous film with good electron conductivity. Perovskite solar cells that contain CBBC‑TIC as the electron‐transport layer achieved a power conversion efficiency of 20.6%, which is comparable to that obtained with the benchmark fullerene derivative [6,6]‐phenyl‐C ₆₁ ‐butyric acid methyl ester (PCBM). Furthermore, the enantiomers of CBBC‐TIC exhibited spin‐selective electron transport arising from the chirality‐induced spin‐selectivity (CISS) effect, with remarkably high enantiospecific magnetic conductance asymmetry values of up to 80% in amorphous films. These findings demonstrate that CBBC represents a versatile molecular component for the creation of advanced non‑fullerene n‐type semiconductors.

The development of a new building block for creating solution‐processable amorphous n‐type semiconductors provides a platform of fundamental importance for advanced organic electronic materials. We have recently demonstrated that oxidative inner‑bond cleavage of readily available dibenzo[ g , p ]chrysene affords a chiral figure‑eight macrocycle that bears electron‑withdrawing carbonyl groups, namely cyclobisbiphenylenecarbonyl (CBBC). In this study, we report a highly electron‑accepting derivative of CBBC (CBBC‑TIC), in which the CBBC core is connected to four electron‑withdrawing dicyanomethylene‑3‑indanone (IC) units via thiophene spacers. The distinctive X‑shaped molecular structure of CBBC‑TIC enables the solution‐process fabrication of a homogeneous amorphous film with good electron conductivity. Perovskite solar cells that contain CBBC‑TIC as the electron‐transport layer achieved a power conversion efficiency of 20.6%, which is comparable to that obtained with the benchmark fullerene derivative [6,6]‐phenyl‐C ₆₁ ‐butyric acid methyl ester (PCBM). Furthermore, the enantiomers of CBBC‐TIC exhibited spin‐selective electron transport arising from the chirality‐induced spin‐selectivity (CISS) effect, with remarkably high enantiospecific magnetic conductance asymmetry values of up to 80% in amorphous films. These findings demonstrate that CBBC represents a versatile molecular component for the creation of advanced non‑fullerene n‐type semiconductors.

Tin-based perovskite solar cells (Sn-PSCs) are fundamentally limited by rapid crystallization, which induces defective morphologies and severe Sn2+ oxidation. Here, we report a combination of 4-fluorophenethylammonium (FPEA) and a pre-annealing static stage (PASS) for Sn-PSCs. While excessive FPEA generates a significant trade-off between grain growth and film compactness, our systematic optimization reveals that an optimal low concentration of FPEA combined with PASS simultaneously mitigates this trade-off. In situ optical spectroscopy reveals an intermediate-mediated stepwise crystallization process, in which a gradual and partial transition from the intermediate to the perovskite phase occurs during PASS, accompanied by effective crystal growth. Subsequent thermal annealing promotes grain reconstruction and healing together with completion of the phase transition. X-ray photoelectron spectroscopy confirms that the electron-withdrawing fluorine atoms modulate the [SnI6]4− electronic landscape and dramatically suppress Sn2+ oxidation. Consequently, the optimized FPEA0.04FA0.96SnI3 films exhibit improved crystalline quality, enlarged grains, and reduced energetic disorder (FA: formamidinium). Their devices deliver a power conversion efficiency of 9.29% (reference: 7.99%) with markedly improved operational stability. This work establishes a clear mechanistic framework and provides a robust design principle for high-performance tin-based perovskites.

Fluoride ion batteries (FIBs) using liquid electrolytes containing quaternary ammonium fluoride salts have recently shown promising room-temperature performance. However, the most commonly used aprotic solvent, bis(2,2,2-trifluoroethyl) ether (BTFE), has a low boiling point (63 °C), making it unsuitable for practical FIB applications. In this study, we substituted BTFE with propylene carbonate (PC), which has a boiling point of 242 °C. We found that the anhydrous quaternary ammonium fluoride, N,N-dimethyl-N,N-dineopentylammonium fluoride (Np2F), was soluble in propylene carbonate at concentrations up to 1.6 M. At 0.9 M, this Np2F/PC electrolyte had an ionic conductivity of 4.7 mS/cm, accompanied by a high fluoride transport number of 0.69 and an exceptionally high electrochemical stability window of 4.2 V. Interestingly, this wide stability was achieved despite the dominant charge carrier being found to be bifluoride, HF2−. The Np2F/PC electrolyte supported reversible fluorination/defluorination in a test cell with BiF3 electrodes at 0.1 C.