Optimization of black diamond films for solar energy conversion

Highlights: • Black diamond films were developed by fs-laser subwavelength surface texturing. • Black diamond films can be used as photon-enhanced thermionic emission devices. • A simple method for developing a 2D periodic surface texturing is proposed. • Although not perfectly regular, the 2D texturing induced a 98% solar absorptance. • The 2D texturing enhances the photoelectronic capability of black diamond films. - Abstract: Black diamond, namely a surface textured diamond film able to absorb efficiently the sunlight, is developed by the use of ultrashort pulse laser treatments. With the aim of fabricating a 2D periodic surface structure, a double-step texturing process is implemented and compared to the single-step one, able to induce the formation of 1D periodic structures. Although the obtained sub-microstructure does not show a regular 2D periodicity, a solar absorptance of about 98% is achieved as well as a quantum efficiency enhanced of one order of magnitude with respect to the 1D periodic surface texturing.