Photon-collection improvement from laser-textured AZO front-contact in thin-film solar cells

With the objective of increasing light scattering and obtaining a higher light absorption in thin-film solar cells, we have textured aluminum-doped zinc oxide (ZnO:Al) films deposited by RF magnetron sputtering on glass substrates using a nanosecond pulsed laser working at 355 nm. The textures have been achieved by simply patterning the ZnO:Al surfaces through direct scribing, using either a linear pattern consisting of equally separated parallel grooves, or a crisscross pattern obtained by performing a second array of laser scribes perpendicular to the former. The relationship between the light scattering properties of the textured films and its morphology are discussed considering two different scattering sources: the pattern formed by the grooves that works as a diffraction grating, and a random roughness of low amplitude created during the laser process. To further characterize the textured samples, amorphous silicon solar cells were deposited onto ZnO:Al films with different textures and their spectral response and short-circuit current (Jsc) measured. An increment of 15% in Jsc compared to non-textured solar cells is achieved, with ample room for improvement.