In the field of perovskite light-emitting diodes (PeLEDs), the performance of blue emissive electroluminescence devices lags behind the other counterparts due to the lack of fabrication methodology. Herein, we demonstrate the in situ fabrication of CsPbClBr₂ nanocrystal films by using mixed ligands of 2-phenylethanamine bromide (PEABr) and 3,3-diphenylpropylamine bromide (DPPABr). PEABr dominates the formation of quasi-two-dimensional perovskites with small-n domains, while DPPABr induces the formation of large-n domains. Strong blue emission at 470 nm with a photoluminescence quantum yield up to 60% was obtained by mixing the two ligands due to the formation of a narrower quantum-well width distribution. Based on such films, efficient blue PeLEDs with a maximum external quantum efficiency of 8.8% were achieved at 473 nm. Furthermore, we illustrate that the use of dual-ligand with respective tendency of forming small-n and large-n domains is a versatile strategy to achieve narrow quantum-well width distribution for photoluminescence enhancement.

After over 30 years of development, colloidal quantum dots have now become mature luminescent materials in photonic and optoelectronic operations and start to hit the market. The emerging perovskite nanocrystals are expected to promote large‐scale commercialization due to their superior optical properties as well as low cost and easy fabrication. This progress report is focused on the developments of in situ fabricated perovskite nanocrystals with attractive features of excellent superior photoluminescence and electroluminescence performance, as well as the solution processability, easy integration, and scale‐up fabrication. These advantages make them suitable candidates as down‐shifting materials for photonics or emissive component for optoelectronics. Recently, the first television demons using composite films based on in situ fabricated perovskite nanocrystals were demonstrated at CES 2018 exhibition, and the performance of electroluminescence devices based on in situ fabricated perovskite nanocrystals is leading the study. It is believed that the in situ fabricated perovskite nanocrystrals will bring a revolution in the field of optical materials after further developments.

This communication describes the use of Ag₂S-encapsulated Au nanorods (AuNR@Ag₂S) to enhance longer wavelength sunlight utility in dye-sensitized solar cells (DSSCs). We observed that the longitudinal plasmon resonance of AuNRs induces a remarkable increase of 37.6% in photocurrent generation at 600–720 nm. Optical characterizations indicate that the increased optical density and decreased light transmission as a result of AuNRs incorporation engender the striking improvement. With AuNR@Ag₂S, the final power conversion efficiency (PCE) of the DSSC with a thin anode (6 μm) increases from 4.3% to 5.6%, which is comparable to that of a pure TiO₂ anode based DSSC (5.8%) with a film thickness of 11 μm. Further, incorporation of AuNR@Ag₂S into the thick anode leads to the PCE increasing to 7.1%.

Integration of gold and titania in a nanoscale core/shell architecture can offer large active metal/semiconductor interfacial areas and avoid aggregation and reshaping of the metal nanocrystal core. Such hybrid nanostructures are very useful for studying plasmon-enhanced/enabled processes and have great potential in light-harvesting applications. Herein we report on a facile route to (gold nanocrystal core)/(titania shell) nanostructures with their plasmon band synthetically variable from ∼700 nm to over 1000 nm. The coating method has also been applied to other mono- and bi-metallic Pd, Pt, Au nanocrystals. The gold/titania nanostructures have been employed as the scattering layer in dye-sensitized solar cells, with the resultant cells exhibiting a 13.3% increase in the power conversion efficiency and a 75% decrease in the scattering-layer thickness. Moreover, under resonant excitation, the gold/titania nanostructures can efficiently utilize low-energy photons to generate reactive oxygen species, including singlet oxygen and hydroxyl radicals.