Why do holes move in the opposite direction from electrons in a semiconductor?

In a semiconductor, a hole represents a missing electron within the crystal's valence band. Because an electron carries a negative charge, its absence is effectively equivalent to a positive electric charge.12

When an electron moves to fill a vacant site (a hole), it leaves behind a new hole at its previous location. This process creates a chain of shifting electron positions that, from a macroscopic perspective, appears as the movement of a positive charge carrier. Under the influence of an electric field, these holes move in the direction of the field, which is inherently opposite to the direction of the negatively charged electrons.12

While both act as charge carriers, holes generally move more slowly than electrons because they are restricted to the tightly bound valence band, whereas free electrons move through the higher-energy conduction band.12