Light can excite electron and hole pairs inside semiconducting materials. If the attraction between a negatively charged electron and a positively charged hole (the antiparticle of electron in solid state physics) is strong, they stay bound together, forming states known as excitons. In these states, positively charged holes can be viewed as the vacancies left behind by the electrons they are paired with.
Click here for original story, Recent manipulations of excitons in moiré superlattices
Source: Phys.org