Achieving balanced charge transport is crucial for high-performance quantum-dot light-emitting diodes (QLEDs), yet it remains a significant challenge. This issue is notably evident when using high-mobility metal oxides, such as ZnO and SnO₂ nanoparticles, as electron transport layers (ETLs), due to their excessive electron mobility which leads to a severe mismatch with most organic hole transport layers (HTLs). Consequently, the balanced charge injection and high efficiency in conventional QLEDs have been largely confined to high-mobility HTLs like poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl) diphenylamine) (TFB). In this study, we present a universal strategy to precisely tune the electron mobility of SnO₂ nanocrystals through controlled Zn²⁺ doping concentration. This approach enables synergistic matching with a range of commonly used HTLs, achieving a near-ideal charge balance across all systems. As a result, we fabricated high-performance QLEDs with universal HTL compatibility, where all optimized devices exhibited a maximum external quantum efficiency (EQE) exceeding 27%. Importantly, the positive aging effect commonly observed in ZnMgO-based devices is completely eliminated in all our SnO₂-based QLEDs. This work provides a general and universal ETL materials for fabricating highly efficient and stable QLEDs compatible with diverse hole transport materials without the need to consider their hole mobility.

Chiral polar metal halides can generate spontaneous polarization, endowing them with potential for self-driven circularly polarized light (CPL) detection. However, most chiral metal halides crystallize in non-polar space groups and cannot generate spontaneous polarization, making efficient self-driven CPL detection difficult. In this work, for the first time, we propose a strategy to induce spontaneous polarization into non-polar chiral halides by introducing free halogens into the halide lattice via a solvothermal method. We find that this strategy not only breaks the intrinsic symmetry of non-polar R/S-MPZPbBr₄ and transforms it into R/S-MPZPbBr₄·0.5Br₂ with the polar space group C2, but also induces larger octahedral distortion, which enhances the circular dichroism anisotropy factor (g_CD) by 8 times. Benefiting from spontaneous polarization and the enhanced g_CD, R/S-MPZPbBr₄·0.5Br₂ exhibits an anomalous photovoltaic effect of 3.8 V under zero bias and enables efficient self‑driven CPL detection, with an anisotropic response factor (g_res) as high as 0.61. Our work opens a new pathway for designing chiral metal halides for self‑driven CPL detection.

Chiral organic-inorganic hybrid halides show significant potential for applications in circularly polarized photodetection, chiral-induced spin selectivity effects (CISS), and nonlinear optics. However, the widespread use of toxic lead element poses environmental concerns, hindering the further applications. Herein, we synthesized a zero-dimensional (0D) lead-free chiral antimony-based halide (R/S-MBA)₄Sb₂Br₁₀ with the coexistence of polarity and crystallographic chirality. The halides exhibit unique magneto-chiroptical effects due to the field-effect-induced fine-tuning of exciton energy, which is the first observation in chiral antimony-based halides. Furthermore, owing to its significant spontaneous polarization (5.0 μC/cm²) and optical chirality (g_CD = 0.0018), (R/S-MBA)₄Sb₂Br₁₀ halide exhibits excellent performance in self-powered circularly polarized photodetection, nonlinear optics, and CISS effects. The self-powered photodetector demonstrates high sensitivity with distinguishable factors (g_res = 0.53/−0.51 @ 0 V) and broad spectral response. The single crystal (R/S-MBA)₄Sb₂Br₁₀ also exhibits a high second-harmonic polarization response asymmetry factor (g_SHG-CD = 0.98/−0.70) and strong second-harmonic generation intensity. These performances are among the best reported for chiral halides. Our research not only sheds new light on the investigation of magneto-chiroptical phenomena, but also marks a significant advancement in realizing high-sensitivity circularly polarized light detection within the realm of lead-free polar materials.

Zero-dimensional metal halides are of unique structures and tunable photoluminescence properties, showing great potential applications such as light-emitting diodes (LEDs) and sensing. Herein, we successfully synthesized Cu⁺ doped (MA)₂ZnCl₄ metal halides by a slow evaporation solvent method. The introduction of Cu⁺ results in sky-blue self-trapped exciton emission in (MA)₂ZnCl₄ at 486 nm at room temperature, and a photoluminescence quantum yield is as high as 54.9%. Interestingly, at low temperatures, Cu⁺-doped (MA)₂ZnCl₄ exhibits two emission peaks located at 482 and 605 nm, respectively. This temperature-dependent dual emission indicates two excited state structures that exist on the triplet excited-state potential energy surface. In addition, the temperature sensor we fitted has good performance (S_r = 1.65 %·K⁻¹), which is the first attempt in Cu⁺ doped Zn-based metal halides. Our work enriches the family of sky-blue metal halides and provides a promising strategy for building sky-blue LEDs.