Lead‐free double perovskites have emerged as a promising class of materials with potential to be integrated into a wide range of optical and optoelectronic applications. Herein, the first synthesis of 2D Cs2AgInxBi1‐xCl6 (0 ≤ x ≤ 1) alloyed double perovskite nanoplatelets (NPLs) with well controlled morphology and composition is demonstrated. The obtained NPLs show unique optical properties with the highest photoluminescence quantum yield of 40.1%. Both temperature dependent spectroscopic studies and density functional theory calculation results reveal that the morphological dimension reduction and In–Bi alloying effect together boost the radiative pathway of the self‐trapped excitons of the alloyed double perovskite NPLs. Moreover, the NPLs exhibit good stability under ambient conditions and against polar solvents, which is ideal for all solution‐processing of the materials in low‐cost device manufacturing. The first solution‐processed light‐emitting diodes is demonstrated using the Cs2AgIn0.9Bi0.1Cl6 alloyed double perovskite NPLs as the sole emitting component, showing luminance maximum of 58 cd m−2 and peak current efficiency of 0.013 cd A−1. This study sheds light on morphological control and composition‐property relationships of double perovskite nanocrystals, paving the way toward ultimate utilizations of lead‐free perovskite materials in diverse sets of real‐life applications.

I–III–VI type semiconductor nanocrystals (NCs) have attracted considerable attention in the display field. Herein, we realized the synthesis of narrow-bandwidth blue-emitting Ag–Ga–Zn–S (AGZS) NCs via a facile one-pot method. Intriguingly, the Ag/Zn feeding ratio and Ag/Ga feeding ratio are crucial for the realization of narrow-bandwidth AGZS NCs. By choosing a Ag/Zn feeding ratio of 4:1 and Ag/Ga feeding ratio of 1:8, AGZS NCs demonstrate a typical blue emission at 470 nm with a narrow full width at half-maximum (fwhm) of 48 nm, which is mainly generated from the band-to-hole recombination rather than the donor–acceptor pair (DAP) recombination. Furthermore, a solution-processed quantum-dot light-emitting device based on AGZS NCs exhibits a narrow electroluminescent bandwidth of 53 nm and high luminance over 123.1 cd m–2, as well as a high external quantum efficiency (EQE) of 0.40%. Our work highlights AGZS NCs with high color purity as an important candidate for blue-light-emitting devices.

Ternary Pb-free Cs−Cu−I perovskites have attracted widespread attention because of their excellent optical properties and environmentally friendly advantages. Herein, two different Pb-free ternary Cs 3 Cu 2 I 5 nanocrystals (NCs) and CsCu 2 I 3 microrods (MRs) were synthesized via a heating method. The phase and morphology transition from blue emission of Cs 3 Cu 2 I 5 NCs to yellow emission of CsCu 2 I 3 MRs could be tuned effectively by manipulating the reaction temperature, decreasing the maximum photoluminescence quantum yields (PLQYs) from 82.7% to ∼10%. More interestingly, the Cs 3 Cu 2 I 5 NCs could self-assemble into stacking chains, which exhibited a strong dependence on the polarity of solvents. In addition, it was demonstrated that the rapid phase transition and luminescence tuning between Cs 3 Cu 2 I 5 and CsCu 2 I 3 films took only a few seconds by direct heating or exposure to the polar solvent. This work may deepen the understanding of the phase transition process in Cu-based perovskites and provide a fluorescence material with a short switching time for anticounterfeiting applications.

Although cadmium (Cd)-based nanocrystals have enabled high-performance quantum-dot light-emitting diodes (QLEDs), their mass production is likely to be affected by environmental protection policies. Among all the potential Cd-free candidates, Cu-In-Zn-S (CIZS) nanocrystals (NCs) have attracted particular interests. Still, the performance of the corresponding LED is currently limited by imbalanced charge injection and luminescence quenching, which are both related to the ZnO-based electron transporting layer (ETL). This work demonstrates that ZnO nanoparticles (NPs) doped with Sn, Mg (Zn 1−x−y Sn x Mg y O), and passivated with Cl are promising to resolve the above issues. All-solution-processed QLEDs based on Cd-free CIZS NCs are fabricated by using Zn 0.9 Sn 0.1 O NPs as the ETL, and the peak external quantum efficiency (EQE max ) was nearly twice that of ZnO (EQE max = 1.74%). The main reason is that the incorporation of Sn can reduce the conductivity of ZnO by an order of magnitude. Combining the advantages of Zn 0.9 Sn 0.1 O, Zn 0.8 Sn 0.1 Mg 0.1 O@Cl NPs are designed by the co-doping of Mg and Cl passivation. The EQE max and current efficiency based on Zn 0.8 Sn 0.1 Mg 0.1 O and Zn 0.8 Sn 0.1 Mg 0.1 O@Cl as ETLs are further increased to 4.84%, 14.00 cd A −1 and 5.53%, 15.99 cd A −1 , respectively. The positive effects of Mg ions can remarkably optimize energy level structure to balance charge injection, while Cl can further passivate defects. The findings offer a new guideline for developing Cd-free light-emitting diodes.

Solution process is a key technique for the manufacture of large-area and low-cost semiconducting devices and, thus, attracts a lot of attention from both academia and industry. Herein, we realized solution-processed light-emitting diodes (excluding a cathode) based on aggregation-induced emission (AIE) molecules of tetraphenylethylene-4Cl (TPE-4Cl) and cadimum-free semiconductor nanocrystals (NCs) for the first time. By mixing Cu-In-Zn-S NCs and TPE-4Cl as an emissive layer, a new type of environmentally friendly white-light-emitting diodes (WLEDs) was prepared through a solution-processed technique. After systematical optimization of the as-prepared WLEDs, the corresponding color rendering index can reach up to 87 with a maximum luminance of 262    cd/ m 2 . This study may pave a new road to realize AIE-based WLEDs through a solution-processed technique.