Cesium lead halide (CsPbX) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce, Sm, Eu, Tb, Dy, Er, and Yb) into the lattices of CsPbCl perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

Quantum cutting can realize the emission of multiple near-infrared photons for each ultraviolet/visible photon absorbed, and has potential to significantly improve the photoelectric conversion efficiency (PCE) of solar cells. However, due to the lack of an ideal downconversion material, it has merely served as a principle in the laboratory until now. Here, the fabrication of a novel type of quantum cutting material, CsPbCl Br :Yb , Ce nanocrystals is presented. Benefiting from the larger absorption cross-section, weaker electron-phonon coupling, and higher inner luminescent quantum yield (146%), the doped perovskite nanocrystals are successfully explored as a downconverter of commercial silicon solar cells (SSCs). Noticeably, the PCE of the SSCs is improved from 18.1% to 21.5%, with a relative enhancement of 18.8%. This work exhibits a cheap, convenient, and effective way to enhance the PCE of SSCs, which may be commercially popularized in the future.

Intracellular pH sensing is of importance and can be used as an indicator for monitoring the evolution of various diseases and the health of cells. Here, we developed a new class of surface-functionalized MXene quantum dots (QDs), TiC, by the sonication cutting and hydrothermal approach and further explored their intracellular pH sensing. The functionalized TiC QDs exhibit bright excitation-dependent blue photoluminescence (PL) originating from the size effect and surface defects. Meanwhile, TiC QDs demonstrate a high PL response induced by the deprotonation of the surface defects. Furthermore, combining the highly pH sensitive TiC QDs with the pH insensitive [Ru(dpp)]Cl, we developed a ratiometric pH sensor to quantitatively monitor the intracellular pH values. These novel MXene quantum dots can serve as a promising platform for developing practical fluorescent nanosensors.

A 2D surface plasmon photonic crystal (SPPC) is achieved by implanting gold nanorods onto the periodic surface apertures of the poly(methyl methacrylate) (PMMA) opal photonic crystals. On the surface of the SPPC, the overall upconversion luminescence intensity of NaYF4 :Yb(3+) , Er(3+) under 980 nm excitation is improved more than 10(3) fold. The device is easily shifted to a transparent flexible substrate, applied to flexible displays.

Recently, various lanthanide ions (Ln 3+ ) have been successfully doped into perovskite quantum dots (PQDs), and the quantum-cutting emission of 2 F 5/2 − 2 F 7/2 for Yb 3+ with a measurable inner efficiency of more than 100% has been discovered and applied as the luminescent converter of solar cells, which has opened a new branch for the application of PQDs. In this work, to further improve the quantum-cutting efficiency of Yb 3+ , the codoping and tridoping methods were used to improve the quantum-cutting emission of PQDs. The Yb 3+ −Ln 3+ (Ln = Nd, Dy, Tb, Pr, Ce) pair-doped CsPbCl x Br y I 3−x−y PQDs were fabricated, with all displaying excitonic emission, narrowband emission of Ln 3+ ions, and quantum-cutting emission of Yb 3+ ions. It was interesting that Yb 3+ −Pr 3+ as well as Yb 3+ −Ce 3+ pairs could effectively sensitize the emission of Yb 3+ , owing to Pr 3+ and Ce 3+ ions offering intermediate energy states close to the exciton transition energy of the PQDs. After host composition optimization and tridoping investigation, overall emissions with a 173% photoluminescence quantum yield (PLQY) were obtained in the Yb 3+ −Pr 3+ −Ce 3+ -tridoped CsPbClBr 2 PQDs. Then, the tridoped PQDs were designed as the down-converter for CuIn 1−x Ga x Se 2 (CIGS) as well as the silicon solar cells, which leads to an enhancement of the power conversion efficiency (PCE) of as high as ∼20%. The modified CIGS was further employed to charge the smart mobile phone, which could largely shorten the charging time from 180 to 150 min. This finding is of great significant for expanding the application fields of the impurity-doped PQDs.

Photoluminescence (PL) of rare earth (RE) ions has been observed in RE ion-doped perovskite nanocrystals (PeNCs); however, the electroluminescence (EL) originating from the RE ions is still not achieved in perovskite light-emitting diodes (PeLEDs). Herein, we demonstrate the first observation of EL from the PeLEDs based on Sm3+-doped CsPbCl3 PeNCs, which is realized by benefiting from the as-prepared Sm3+-doped CsPbCl3 PeNCs with photoluminescence quantum yield (PLQY) as high as 85% synthesized through a modified hot-injection method. The color of the EL can be modulated from the blue to the orange spectral region by varying the Sm3+ ion doping concentration. Therefore, the single-component white light-emitting PeLEDs with chromaticity coordinate (CIE) of (0.32, 0.31), a maximum luminance of 938 cd/m2, EQE of 1.2%, and color rendering index (CRI) of 93 are realized, which are desirable results for practical application. This work demonstrates the unique application of RE-doped PeNCs and provides a strategy for devices using white light PeLEDs.

Localized surface plasmon resonances (LSPRs) are achieved in heavily doped semiconductor nanoparticles (NPs) with appreciable free carrier concentrations. In this paper, we present the photonic, electric, and photoelectric properties of plasmonic Cu2-xS NPs/films and the utilization of LSPRs generated from semiconductor NPs as near-infrared antennas to enhance the upconversion luminescence (UCL) of NaYF4:Yb(3+),Er(3+) NPs. Our results suggest that the LSPRs in Cu2-xS NPs originate from ligand-confined carriers and that a heat treatment resulted in the decomposition of ligands and oxidation of Cu2-xS NPs; these effects led to a decrease of the Cu(2+)/Cu(+) ratio, which in turn resulted in the broadening, decrease in intensity, and red-shift of the LSPRs. In the presence of a MoO3 spacer, the UCL intensity of NaYF4:Yb(3+),Er(3+) NPs was substantially improved and exhibited extraordinary power-dependent behavior because of the energy band structure of the Cu2-xS semiconductor. These findings provide insights into the nature of LSPR in semiconductors and their interaction with nearby emitters and highlight the possible application of LSPR in photonic and photoelectric devices.

The performance of perovskite solar cells (PSCs) strongly depends on the electron transport layer (ETL), perovskite absorber, hole transport layer (HTL), and their interfaces. Herein, the first approach to utilize ultrathin 2D titanium‐carbide MXenes (Ti3C2Tx quantum dots, TQD) by engineering the perovskite/TiO2 ETL interface and perovskite absorber and introducing Cu1.8S nanocrystals to perfect the Spiro‐OMeTAD HTL is represented. A significant hysteresis‐free power conversion efficiency improvement from 18.31% to 21.64% of PSCs is achieved after modifications with the enhanced short‐circuit current density, open‐circuit voltages, and fill factor. Various advanced characterizations, including femtosecond transient absorption spectroscopy, electrochemical impedance spectroscopy, and ultraviolet photoelectron spectroscopy, elucidate that the TQD/Cu1.8S significantly contribute to the improved crystalline quality of the perovskite film with its large grain size and improved electron/holes extraction efficiencies at perovskite/ETL and perovskite/HTL interfaces. Furthermore, the long‐time ambient and light stability of PSCs are largely boosted through the TQD and/or Cu1.8S nanocrystals doping, originating from the better crystallization of perovskite, suppressing the film aggregation and crystallization of HTL, and inhibiting the ultraviolet‐induced photocatalysis of the ETL. The findings highlight the TQD and Cu1.8S can act as a superfast electrons and holes tunnel for the optoelectronic devices.