Effect of front-contact laser texturing in thin-film solar cells

This work presents results on laser texturing of aluminum-doped zinc oxide (ZnO:Al) films, a transparent conductive oxide (TCO), for improving light management in thin-film solar cells. Surface texturing is a fundamental step in solar cell manufacturing, especially in thin-film technologies, in order to decrease surface reflectance and enhance light scattering to improve light absorption in the PV absorbent. The ZnO:Al films used in this work were deposited by RF magnetron sputtering on glass substrates, and we used a Diode Pumped Solid State (DPSS) laser source emitting at 355 nm for texturing. All textures were obtained using a direct scribing technique and two different geometrical approaches for patterning were tested: The first consists in a simple linear pattern of equally-spaced parallel grooves while the second approach defines a crisscross pattern obtained by performing a second array of laser scribes orthogonal to the one defined in the first approach. We discuss the results attending at the morphological, optical and electrical characteristics of the samples, measuring the haze behavior and discussing the contribution of two possible scattering sources: The welldefined geometrical pattern formed by the grooves, acting as a diffraction grating, and a random roughness of low amplitude created during the laser process. Finally we deposited amorphous silicon solar cells onto the textured ZnO:Al films and studied the effect in the spectral response and short-circuit current (Jsc). We found, with the appropriate process parameters, an increment of 15% in Jsc compared to non-textured solar cells.