The diode comprises an organic electroluminescent layer interposed between a lower electrode and a partially transparent and semireflective upper electrode, which itself comprises a transparent conducting sublayer and a current-distributing metal sublayer, for example an opaque grid. A dielectric antireflection layer is deposited on the grid to improve the emission contrast in ambient light, which grid, according to an advantageous embodiment, is designed to optimize the semireflective properties of the upper electrode, thereby improving, by an optical cavity effect, extraction of the emitted light.