Polaron formation in two-dimensional bismuth oxyhalides BiOX (X = Cl, Br, I)

Bismuth oxyhalides BiOX (X = Cl, Br, I) have garnered widespread attention in the field of photocatalysis due to their unique layered structures and excellent optoelectronic properties. Based on first-principles calculations, we investigated the formation of electron-phonon coupled polarons in bismuth oxyhalides BiOX (X = Cl, Br, I) using the EPW code. Our calculation results show that hole polarons in BiOX (X = Cl, Br, I) tend to be localized, with formation energies ranging from -0.332 to -0.253 eV, whereas electron polarons form large polarons, with formation energies in the range of -0.076 to -0.004 eV. As the atomic number of the halogen increases, the polaron formation energy gradually increases, the degree of localization weakens, and the system exhibits a more pronounced delocalization trend. Simultaneously, our study provides a detailed enumeration of the phonon and electronic contributions to the polarons. This research provides new insights into the physical properties of polarons in bismuth oxyhalides BiOX (X = Cl, Br, I) and offers guidance for understanding and exploring polarons in related materials.