Solar cell, photonic crystal substrate, solar cell panel, and device provided with solar cell

A solar cell (1) is provided with: a photonic crystal structure (30) that is formed on the surface of a first transparent conductive film (11) on the light incident side; and a photoelectric conversion layer (20) that is formed along the recesses and projections of the photonic crystal structure (30). The first transparent conductive film (11) and the photonic crystal structure (30) have smaller refractive indexes than the photoelectric conversion layer (20).