Pai Geng

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

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.

Perovskite light‐emitting devices (peLEDs) have recently gained widespread attention as candidates for next‐generation display technologies. Red and green peLEDs have achieved over 20% external quantum efficiency (EQE), however blue peLEDs still lag behind. One proposed solution for improving the performance of blue peLEDs has been doping the perovskite films with metal ions, ostensibly to passivate surface trap sites and improve the EQE. Despite a few recent reports, however, the many roles of the metal ion dopants have not yet been fully explored. Here improvements in the EQE and spectral stability of quasi‐2D perovskites, often called 2D/3D or layered perovskites are reported. CsPbBr_3−xCl_x sky‐blue emitting peLEDs, with a maximum EQE of 7.5%, and color stable spectra at high applied voltages are achieved, via doping with divalent metal ions at concentrations of 0.5 to 10%, by mole ratio. After screening several candidates, two metal ions are identified, Mn²⁺ and Mg²⁺ that are particularly effective, as compared with PEA‐based quasi‐2D control devices. Then these examples are used to study the effect of metal ions more generally on the film morphology, the hole transport layer's conductivity, the trap density, and the energy funneling dynamics, all of which strongly influence the device performance.

We summarize the structures, synthesis and properties of copper-based ternary metal halides, and their applications in optoelectronics, along with a perspective and suggestions for the future directions for this class of copper compounds.