Carbon dots (CDs) with an emission in the near infrared spectral region are attractive due to their promising applications in bio-related areas, while their fabrication still remains a challenging task. Herein, we developed a template-assisted method using porous silica microspheres for the formation of CDs with optical transitions in the near infrared. Two organic dyes, Rhodamine 6G and IR1061 with emission in the yellow and near infrared spectral regions, respectively, were used as precursors for CDs. Correlation of morphology and chemical composition with optical properties of obtained CDs revealed the origin of their emission, which is related to the CDs’ core optical transitions and dye-derivatives within CDs. By varying annealing temperature, different kinds of optical centers as derivatives of organic dyes are formed in the microsphere’s pores. The template-assisted method allows us to synthesize CDs with an emission peaked at 1085 nm and photoluminescence quantum yield of 0.2%, which is the highest value reported so far for CDs emitting at wavelengths longer than 1050 nm.

Metal halide perovskite nanocrystals (NCs) attract much attention for light-emitting applications due to their exceptional optical properties. More recently, perovskite NCs have begun to be considered a promising material for nonlinear optical applications. Numerous strategies have recently been developed to improve the properties of metal halide perovskite NCs. Among them, B-site doping is one of the most promising ways to enhance their brightness and stability. However, there is a lack of study of the influence of B-site doping on the nonlinear optical properties of inorganic perovskite NCs. Here, we demonstrate that Cd²⁺ doping simultaneously improves both the linear (higher photoluminescence quantum yield, larger exciton binding energy, reduced trap states density, and faster radiative recombination) and nonlinear (higher two- and three-photon absorption cross-sections) optical properties of CsPbBr₃ NCs. Cd²⁺ doping results in a two-photon absorption cross-section, reaching 2.6 × 10⁶ Goeppert-Mayer (GM), which is among the highest reported for CsPbBr₃ NCs.

Semiconductor colloidal nanoplatelets (NPLs) are a promising new class of nanostructures that can bring much impact on lightning technologies, light-emitting diodes (LED), and laser fabrication. Indeed, great progress has been made in optimizing the optical properties of the NPLs for the visible spectral range, which has already made the implementation of a number of effective devices on their basis possible. To date, state-of-the-art near-infrared (NIR)-emitting NPLs are significantly inferior to their visible-range counterparts, although it would be fair to say that they received significantly less research attention so far. In this study, we report a comprehensive analysis of steady-state and time-dependent photoluminescence (PL) properties of four monolayered (ML) PbSe NPLs. The PL measurements are performed in a temperature range of 78–300 K, and their results are compared to those obtained for CdSe NPLs and PbSe quantum dots (QDs). We show that multiple emissive states, both band-edge and trap-related, are responsible for the formation of the NPLs’ PL band. We demonstrate that the widening of the PL band is caused by the inhomogeneous broadening rather than homogeneous one, and analyze the possible contributions to PL broadening.

Iodide atomic surface passivation of lead chalcogenides has spawned a race in efficiency of quantum dot (QD)-based optoelectronic devices. Further development of QD applications requires a deeper understanding of the passivation mechanisms. In the first part of the current study, we compare optics and electrophysical properties of lead sulfide (PbS) QDs with iodine ligands, obtained from different iodine sources. Methylammonium iodide (MAI), lead iodide (PbI₂), and tetrabutylammonium iodide (TBAI) were used as iodine precursors. Using ultraviolet photoelectron spectroscopy, we show that different iodide sources change the QD HOMO/LUMO levels, allowing their fine tuning. AFM measurements suggest that colloidally-passivated QDs result in formation of more uniform thin films in one-step deposition. The second part of this paper is devoted to the PbS QDs with colloidally-exchanged shells (i.e., made from MAI and PbI₂). We especially focus on QD optical properties and their stability during storage in ambient conditions. Colloidal lead iodide treatment is found to reduce the QD film resistivity and improve photoluminescence quantum yield (PLQY). At the same time stability of such QDs is reduced. MAI-treated QDs are found to be more stable in the ambient conditions but tend to agglomerate, which leads to undesirable changes in their optics.

Due to their high resonant third-order nonlinear response, lead sulfide quantum dots (QDs) are potential materials for applications in the field of nonlinear optics. In this paper, we implement the Z-scan method to study the resonant nonlinear response of lead sulfide QDs in colloidal solutions. We managed to measure the purely intrinsic resonant nonlinear response, free of thermal contribution. We report that the lead sulfide QD third-order nonlinear response per QD shows an unconventional increase. A figure of merit for QD nonlinearity grows as a power function with a factor of 2.9.