Dezhang Chen

Quasi‐2D metal‐halide perovskite LEDs (PeLEDs) are promising for displays but remain limited by trap‐mediated loss and short lifetimes, especially in the blue. Here, we report a triple‐cation A‐site doping strategy by co‐incorporating Rb ⁺ and guanidinium (GA ⁺ ) with Cs ⁺ to simultaneously improve efficiency and stability. Rb ⁺ contracts the lattice and extends the radiative lifetime, whereas GA ⁺ predominantly passivates surface and interfacial defects and moderates the quasi‐2D phase distribution. Together they extend photoluminescence lifetimes and suppress trap‐assisted nonradiative pathways, as confirmed by time‐resolved photoluminescence and trap analyses. We further augment the device performance by a yttrium additive and a modified hole‐injection layer. The optimized sky‐blue devices achieve an external quantum efficiency of 9.0% at 492 nm and the operating lifetime ( T ₅₀ ) over 18 min at 100 cd m ⁻² . This synergy between A‐site alloying, additive engineering, and HTL modification provides a practical route toward efficient, more stable sky‐blue quasi‐2D PeLEDs.

Here, we observed chiroptical evolution during the synthesis of perovskite nanocrystals (NCs). Using a steric-delayed nucleation strategy, we slowed the ripening of NCs and observed changes in the circular dichroism (CD) signal of perovskite NCs. Two chiroptical evolution events occurred during NC formation under different conditions, attributed to ligand displacement and NC self-assembly, respectively. Surface characterization and computational studies demonstrate that the ligands initially bind to the NC surface and dissociate during the ripening stage, offering the time window to observe and enhance the intrinsic chirality. Our findings provide a new strategy for studying and designing intrinsically chiral perovskite nanostructures.

0D, 1D, and 2D nanomaterials for quantum information application, showcasing their dimensional advantages in coherence, scalability, and efficient qubit manipulation.

Chiral semiconducting nanomaterials offer many potential applications in photodetection, light emission, quantum information, and so on. However, it is difficult to achieve a strong circular dichroism (CD) signal in semiconducting nanocrystals (NCs) due to the complexity of chiral ligand surface engineering and multiple, uncertain mechanisms of chiroptical behavior. Here, a chiral ligand exchange strategy with cysteine on the ternary metal chalcogenide AgBiS ₂ NCs is developed, and a strong, long‐lasting CD signal in the near‐UV region is achieved. By carefully optimizing the ligand concentration, the CD peaks are observed at 260 and 320 nm, respectively, giving insight into the different ligand binding mechanisms influencing the CD signal of AgBiS ₂ NCs. Using density‐functional theory, a large degree of crystal distortion by the bidentate mode of ligand chelation, and efficient ligand‐NC electron transfer, synergistically resulting in the strongest CD signal (g‐factor over 10 ⁻² ) observed in chiral ligand‐exchanged semiconductor NCs to date, is demonstrated. To demonstrate the effective chiral properties of these AgBiS ₂ NCs, a spin‐filter device with over 86% efficiency is fabricated. This work represents a considerable leap in the field of chiral semiconductor NCs and points toward their future applications.

Indoor photovoltaics (IPVs) are garnering increasing attention from both the academic and industrial communities due to the pressing demand of the ecosystem of Internet‐of‐Things. All‐polymer solar cells (all‐PSCs), emerging as a sub‐type of organic photovoltaics, with the merits of great film‐forming properties, remarkable morphological and light stability, hold great promise to simultaneously achieve high efficiency and long‐term operation in IPV's application. However, the dearth of polymer acceptors with medium‐bandgap has impeded the rapid development of indoor all‐PSCs. Herein, a highly efficient medium‐bandgap polymer acceptor (PYFO‐V) is reported through the synergistic effects of side chain engineering and linkage modulation and applied for indoor all‐PSCs operation. As a result, the PM6:PYFO‐V‐based indoor all‐PSC yields the highest efficiency of 27.1% under LED light condition, marking the highest value for reported binary indoor all‐PSCs to date. More importantly, the blade‐coated devices using non‐halogenated solvent (o‐xylene) maintain an efficiency of over 23%, demonstrating the potential for industry‐scale fabrication. This work not only highlights the importance of fine‐tuning intramolecular charge transfer effect and intrachain coplanarity in developing high‐performance medium‐bandgap polymer acceptors but also provides a highly efficient strategy for indoor all‐PSC application.

Despite recent advances, it is still difficult to fabricate deep blue‐emitting perovskite light‐emitting diodes (LEDs) that are immune to the color instability caused by halide mixing. This is largely because it is still challenging to achieve bright, stable, pure bromide perovskite materials with deep blue emission. Here, a novel strategy is reported for synthesizing ultrasmall CsPbBr₃ quantum dots (QDs) under ambient conditions. Precise size control is used to tune the peak emission wavelengths, via the confinement effect, from 433 to 501 nm. These ultrasmall QDs, with sizes of 2–6 nm, exhibit ultralow trap density and stable photoluminescence quantum yields up to 94%, particularly in the deep blue spectral region (440–465 nm). QD‐LEDs fabricated with these materials achieve an external quantum efficiency of 1.0% at 459 nm. The exceptional control of the emission properties demonstrated here suggests a new strategy for building stable, efficient blue QD‐LEDs.

Singlet fission is a process by which an organic semiconductor is able to generate two triplet excitons from a single photon. If charges from the triplets can be successfully harvested without heavy losses in energy, then this process can enable a single‐junction solar cell to surpass the Shockley–Queisser limit. While singlet fission processes are commonly observed in several materials, harvesting the resulting triplets is difficult and has been demonstrated with only a few transport materials. Here, transient absorption spectroscopy is used to investigate singlet fission and carrier transfer processes at the AgBiS₂/pentacene (AgBiS₂/Pc) heterojunction. The successful transfer of triplets from pentacene to AgBiS₂ and the transfer of holes from AgBiS₂ to pentacene is observed. Further singlet fission in pentacene by modifying the crystallinity of the pentacene layer and have fabricated the first singlet fission AgBiS₂/Pc solar cell is enhanced. Singlet fission devices exhibit higher external quantum efficiency compared with the control devices, and thus demonstrating the significant contribution of charges from the singlet fission process.