In Situ Grown Ultrafine RuO2 Nanoparticles on GeP5 Nanosheets as the Electrode Material for Flexible Planar Micro-Supercapacitors with High Specific Capacitance and Cyclability

GeP₅, as the most representative phosphorus-based material in two-dimensional layered phosphorous compounds, has shown a fairly bright application prospect in the field of energy storage because of its ultrahigh electrical conductivity. However, high-yield exfoliation methods and effective structure construction strategies for GeP₅ nanosheets are still missing, which completely restricts the further application of GeP₅-based nanocomposites. Here, we not only improved the yield of GeP₅ nanosheets by a liquid nitrogen-assisted liquid-phase exfoliation technique but also constructed the GeP₅@RuO₂ nanocomposites with the 0D/2D heterostructure by in situ introduction of ultrafine RuO₂ nanoparticles on highly conductive GeP₅ nanosheets using a simple hydrothermal synthesis method, and then applying it to micro-supercapacitors (MSCs) as electrode materials through a mask-assisted vacuum filtration technique. It is precisely because of the synergy of the electrical double-layer material, GeP₅ nanosheets and the pseudocapacitance material RuO₂ nanoparticles that endows the GeP₅@RuO₂ electrode with outstanding electrochemical performance in micro-supercapacitors with a large specific capacitance of 129.5 mF cm^-2/107.9 F cm^-3, high energy density of 17.98 μWh cm^-2, remarkable long-term cycling stability with 98.4% capacitance retention after 10 000 cycles, the exceptional mechanical stability, outstanding environmental stability, and excellent integration features. This work opens up a new avenue to construct GeP₅-based nanocomposites as a most promising novel electrode material for practical application in flexible portable/wearable micro-nanoelectronic devices.

Self-Assembled High Quality CsPbBr3 Quantum Dot Films toward Highly Efficient Light-Emitting Diodes

Full inorganic cesium lead halide perovskites (IOPs) are regarded as attractive candidates for light-emitting diodes (LEDs) by their excellent luminescent conversion. However, unsatisfactory efficiency and stability are still the main drawbacks that hinder the commercialization progress of perovskite LEDs (PeLEDs). Here, we report an extremely uniform and flat CsPbBr₃ film composing of self-assembly core-shell structured quantum dots (SCQDs) based on one-step precursor coating. The QDs size in the CsPbBr₃ film is around 4.5 nm (smaller than the Bohr radius), which significantly confines injected carriers and leads to a ultrahigh exciton binding energy ( E_b) of 198 meV. In addition, unfavorable surfacial defects are dramatically passivated by a thin surfacial-capping layer composed of long-chain ammonium groups (phenylalanine bromide, PPABr), resulting in an ultralow nonradiative recombination rate. Consequently, the CsPbBr₃ SCQDs film presents a high photoluminescence quantum yield (PLQY) of 85%. It enables the resulting green PeLEDs to deliver a recorded external quantum efficiency (EQE) over 15% with ideal operational stability. Furthermore, the developed CsPbBr₃ SCQDs film also demonstrates promising potential in multifunctional lighting sources such as flexible and smart devices.

Efficient and High-Color-Purity Light-Emitting Diodes Based on In Situ Grown Films of CsPbX3 (X = Br, I) Nanoplates with Controlled Thicknesses

We report a facile solution-based approach to the in situ growth of perovskite films consisting of monolayers of CsPbBr₃ nanoplates passivated by bulky phenylbutylammonium (PBA) cations, that is, two-dimensional layered PBA₂(CsPbBr₃)_n-1PbBr₄ perovskites. Optimizing film formation processes leads to layered perovskites with controlled n values in the range of 12-16. The layered perovskite emitters show quantum-confined band gap energies with a narrow distribution, suggesting the formation of thickness-controlled quantum-well (TCQW) structures. The TCQW CsPbBr₃ films exhibit smooth surface features, narrow emission line widths, low trap densities, and high room-temperature photoluminance quantum yields, resulting in high-color-purity green light-emitting diodes (LEDs) with remarkably high external quantum efficiencies (EQEs) of up to 10.4%. The solution-based approach is extended to the preparation of TCQW CsPbI₃ films for high-color-purity red perovskite LEDs with high EQEs of up to 7.3%.