High-performance tandem LSCs fabricated using N-doped carbon dots and AIE fluorescent materials can be obtained.

Conventional synthesis of carbon dots (CDs) mostly involves a hydrothermal or solvent‐thermal reaction which needs relatively high temperature and pressure. In this work, ionic liquid is used to assist in fast synthesizing CDs with an ultrahigh photoluminescent quantum yield (98.5%) by heating at a low temperature (≤100 °C) and at atmospheric pressure. In addition, through this approach, tunable multicolor emissive CDs can be successfully achieved and used for preparing high‐performance white light‐emitting diodes. Theoretical computation proves that the activity of synthesis reaction can be significantly enhanced by ionic liquids. Density functional theory calculation reveals that the size and graphite nitrogen ratios of CDs have an effect on bandgap reduction, resulting in a redshift of the emission, which is in good agreement with the experimental results. This simple and promising approach for fast synthesis of tunable emissive CDs using ionic liquid affords the facilitation of CDs‐based luminescent materials for fast manufacturing of functional devices.

Lead‐free perovskites have gained much interest for photovoltaic and optoelectronic applications. But instability and low quantum efficiency significantly limit their prospects for future applications. Here, a general route is reported to synthesize highly stable lead‐free perovskites on a large scale with remarkably enhanced quantum efficiency. Two typical vacancy‐ordered double perovskites (Cs2ZrCl6 and Cs2SnCl6) and their corresponding Bi3+ or Sb3+ doped samples are synthesized in ionic liquids (ILs) solutions via a simple solution method. These prepared perovskite samples all exhibit high‐quality crystalline structures and their photoluminescence quantum yields (PLQYs) all show an increase close to 200% compared to the samples prepared in the hydrochloric acid system. The PLQY of Sb‐doped Cs2ZrCl6 with excellent thermal stability can reach up to 90.2%, which is the highest value reported for this system (Cs2ZrCl6:Sb). Density functional theory calculations reveal that the corresponding interaction between the ILs and the samples can effectively improve the crystal quality and reduce energy loss. The potential applications of the prepared samples for high‐performance white light‐emitting diodes and optical anti‐counterfeiting are also demonstrated. The findings provide a straightforward way to obtain ultrahigh quantum efficiency vacancy‐ordered double perovskites with good thermal stability and excellent optoelectronic properties.

Lithium iron phosphate (LiFePO4) is widely applied as the cathode material for the energy storage Li‐ion batteries due to its low cost and high cycling stability. However, the low theoretical specific capacity of LiFePO4 makes its initial capacity loss more concerning. Therefore, lithium compensation by way of prelithiation and applications of sacrificial Li‐rich additives in LiFePO4 is imminent in elevating the energy density and/or prolonging the lifetime of the LiFePO4‐based Li‐ion batteries (LIBs). Prelithiation in LiFePO4 is herein carried out by electrochemical and chemical methods and its feasibility is proved on the basis of the electrochemical evaluations such as the initial charge capacity and the cycling stability. In addition, the site of the pre‐intercalated Li‐ions is found via comprehensive physical characterizations and the density functional theory (DFT) calculations. These findings open a new avenue for elevating the energy density and/or prolonging the lifetime of the high‐energy‐density batteries.