Strategies To Achieve Long-Term Stability in Lead Halide Perovskite Nanocrystals and Its Optoelectronic Applications.

The lead halide perovskite (LHP) nanocrystals (NCs) research area is flourishing due to their exceptional properties and great potential for a wide range of applications in optoelectronics and photovoltaics. Yet, despite the momentum in the field, perovskite devices are not yet ready for commercialization due to degradation caused by intrinsic phase transitions and external factors such as moisture, temperature, and ultraviolet (UV) light. To attain long-term stability, we analyze the origin of instabilities and describe different strategies such as surface modification, encapsulation, and doping for long-term viability.

Evidence of Short-Lived High-Energy Emissive State and Triplet Character of the Self-Trapped Exciton in CsCuI Perovskite.

CsCuI perovskite displays a Stokes-shifted photoluminescence (PL) at 445 nm, attributed to the self-trapped excitons (STEs). Unlike that observed in other perovskite materials, the free-exciton emission is not evidenced in this case. Herein, we reveal the existence of a short-lived high-energy emission centered around 375 nm through the reconstruction of time-resolved emission spectra (TRES), which is independent of the shape/size of CsCuI perovskite.

Red-emitting polyaniline-based nanoparticle probe for pH-sensitive fluorescence imaging.

Fluorescent probes based on semiconducting polymer nanoparticles (NPs) such as polyaniline (PANI) usually require external fluorophore doping to provide fluorescence function. Direct use of PANI-based NPs for bioimaging applications has been limited by PANI's weak blue fluorescence and aggregation-induced quenching in physiological medium. In this report, we developed a facile solid-state synthesis method to produce fluorescent polyaniline nanoparticles (FPNs) that are not only water-soluble but also exhibit high intensity and pH-sensitive red fluorescence.

Potassium-Induced Passivation of Deep Traps in Bismuth-Doped Hybrid Lead Bromide Perovskite Nanocrystals: Massive Amplification of Photoluminescence Quantum Yield.

The low photoluminescence quantum yield of Bi-doped lead halide perovskite nanocrystals (NCs) is a big challenge to the scientific community. This makes them a weak candidate in the optoelectronics field in spite of their better stability than the pure lead analogue. Herein, the reason behind this reduction of quantum yield in hybrid mixed lead-bismuth bromide (MPBBr) NC is investigated and proposed to be due to ultrafast trapping transfer in the core of the NC, and not due to the surface trap states.

Reversible Ultra-Slow Crystal Growth of Mixed Lead Bismuth Perovskite Nanocrystals: The Presence of Dynamic Capping.

An ultra-slow crystal growth over a period of 24 h of a newly synthesized CH NH Pb Bi I perovskite (MPBI) nanocrystal in non-polar toluene medium is reported here. From several spectroscopic techniques as well as from TEM analysis we found that the size of nanocrystals changes continuously with time, in spite of being capped by the ligands. Using a single molecular spectroscopic technique, we also found that this size change is not due to the stacking of nanocrystals but due to crystal growth.