A (111) Facet‐Dominated Carbon Dots‐Perovskite Composite Crystal Matrix for Highly Stable Photodetector

Abstract Crystal facet orientation plays a key role in dominating the optoelectronic conversion and stability of perovskite devices. To date, in‐depth understanding on how to control the orientation of crystal facet and its’ effect on the optoelectronic properties of perovskites remains a significant challenge. Here, a strategy for manipulating the facet orientation of methylammonium lead bromide (MAPbBr₃) perovskite single crystals utilizing carbon dots (CDs) is proposed, which can expose the (111) facet by reducing the surface energy of specific crystal facets selectively and improve the optoelectronic properties by CDs incorporation simultaneously. Experimental and theoretical studies indicate that the CDs are prefer to adsorb on the (111) facet and the (111) facet‐dominated CDs‐perovskite composite crystal matrixes exhibit significantly improved optoelectronic properties compared to perovskite crystal dominated by the (100) facet Consequently, the (111) facet‐dominated perovskite photodetector demonstrates exceptional performance, with a responsivity as high as 249.09 A W⁻¹ and a detectivity of 1.19 × 10¹⁴ Jones. More significantly, the unencapsulated photodetector shows remarkable stability, maintaining a record 93% of its initial performance over 90 d. This work provides a novel way to enhance the performance of halide perovskites photodetectors by crystal facet orientation modulation strategy, especially the stability.