Crystallinity and defect reduction in Cs2AgBiBr6: Key factors for enhanced optoelectronic devices

Cs₂AgBiBr₆ double perovskites have attracted considerable interest for optoelectronic applications owing to their favorable structural stability and nontoxic composition. In this study, we systematically investigate the influence of two crystal growth methods—Single Crystal Growth (SCG) and Seed-Assisted Growth (SAG)—on the morphology, crystallinity, defect landscape, and optoelectronic properties of Cs₂AgBiBr₆ single crystals. Comprehensive characterization using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), time-resolved photoluminescence (TRPL), impedance spectroscopy, and current–voltage (I–V) measurements reveals that the SAG method yields significantly larger and more uniform grains, improved structural coherence, and reduced defect densities compared to the SCG route. The narrower XRD peaks and reduced lattice strain in SAG-grown crystals confirm their higher crystallinity, while TRPL analysis shows extended carrier lifetimes, indicating suppressed nonradiative recombination due to fewer trap states. These structural and optical improvements directly enhance device performance, as SAG-grown crystals exhibit a 2.5-fold increase in photocurrent and a markedly lower dark current in photodetector configurations. Our findings establish the SAG technique as a superior and scalable approach for producing high-quality Cs₂AgBiBr₆ crystals, positioning them as promising candidates for next-generation optoelectronic devices, including photodetectors and light-emitting components.