Formation of nanostructures on the surface of CIGS films by picosecond laser with different beam patterns

As direct band gap semiconductor, CIGS thin film solar cells has developed rapidly in recent years. Nano-ripples on transparent layer of CIGS solar cells can improve the light absorption. The photoelectric conversion efficiency improved and the thickness of solar cell decreased with the requirement of optical absorptivity. This study proposed a key technological point concerning the obtainment of perfect LIPSSs using picosecond laser with different beam pattern. Linear sweep in parallel to the laser polarization direction was performed using a Nd:VAN laser system with 10-ps Qswitched pulsed at a central wavelength of 532 nm with a repetition rate of 1 kHz. The nanostructure with different characteristics were obtained at different laser fluence and scanning speed which was focused with circular spot. The linear spot pattern can improve the processing efficiency greatly. In this way, three kind of morphologies were obtained successfully at the same parameter, which was useful for processing different kind of nanostructures. To our knowledge, it is the first time that we report the LIPSSs formed on CIGS absorber layers. Thus, the proposed technique can be considered to be a promising method for the laser machining of special nonmetal films.