A team of researchers from Changchun Institute of Optics, Fine Mechanics and Physics at the Chinese Academy of Sciences developed a method to improve the stability and performance of perovskite photodetectors by controlling crystal facet orientation with carbon dots (CDs). Their work, published in Small, demonstrated that CDs preferentially adsorb on the (111) facet of methylammonium lead bromide (MAPbBr₃) perovskite, reducing surface energy and enhancing optoelectronic properties.

The researchers grew perovskite single crystals using an inverse temperature crystallization method and introduced CDs into the precursor solution. X-ray diffraction and transmission electron microscopy revealed that CDs transformed the crystal morphology from (100)-dominant to (111)-dominant. Density functional theory calculations showed CDs had stronger binding energy with the (111) facet, aligning with experimental observations.

The (111)-dominant perovskite exhibited superior charge carrier mobility (22.40 cm² V⁻¹ s⁻¹) and lower trap density compared to the (100)-dominant crystal. Photodetectors fabricated from the (111)-dominant matrix achieved a responsivity of 249.09 A W⁻¹ and detectivity of 1.19 × 10¹⁴ Jones. Remarkably, unencapsulated devices retained 93% of their initial performance after 90 days in ambient conditions, attributed to the (111) facet’s resistance to moisture.

This study highlights the critical role of crystal facet engineering in perovskite optoelectronics. By leveraging CDs to modulate facet orientation, the team addressed stability challenges without compromising performance. The findings offer a practical strategy for developing durable perovskite-based photodetectors for applications in imaging, sensing, and optical communication.