Highly Emissive Lanthanide‐Based 0D Metal Halide Nanocrystals for Efficient Ultraviolet Photodetector

Recently, lanthanide‐based 0D metal halides have attracted considerable attention for their applications in X‐ray imaging, light‐emitting diodes (LEDs), sensors, and photodetectors. Herein, lead‐free 0D gadolinium‐alloyed cesium cerium chloride (Gd3+‐alloyed Cs3CeCl6) nanocrystals (NCs) are introduced as promising materials for optoelectronic application owing to their unique optical properties. The incorporation of Gd3+ in Cs3CeCl6 (CCC) NCs is proposed to increase the photoluminescence quantum yield (PLQY) from 57% to 96%, along with significantly enhanced phase and chemical stability. The structural analysis is performed by density functional theory (DFT) to confirm the effect of Gd3+ in Cs3Ce1‐xGdxCl6 (CCGC) alloy system. Moreover, the CCGC NCs are applied as the active layer in UVPDs with different Gd3+ concentration. The excellent device performance is shown at 20% of Gd3+ in CCGC NCs with high detectivity (7.938 × 1011 Jones) and responsivity (0.195 A W−1) at ‐0.1 V at 310 nm. This study paves the way for the development of lanthanide‐based metal halide NCs for next‐generation UVPDs and other optoelectronic applications. Cs3CeCl6 (CCC) nanocrystals (NCs) possess fascinating optical properties due to their f–d coupling of Ce3+ ions. The incorporation of Gd3+ in CCC NCs can be a facile method to enhance photoluminescence quantum yield (PLQY) up to almost unity (96%) as well as the phase stability. This Cs3Ce1‐xGdxCl6 alloyed NCs exhibits efficient device performance as a UV‐light absorbing layer for photodetector with detectivity (7.938 × 1011 Jones) and responsivity (0.195 A W−1) at ‐0.1 V bias at 310 nm.