Rapid sub-wavelength texturing for III?V solar cells by laser interference lithography and wet etching

Optimization of non-planar antireflective coating and back- or front- surface texturing are widely studied to further reduce the reflection losses and increase the sunlight absorption path in solar cells.. Back reflectors have been developed from perfect mirror to textured mirror in order to further increase light path, which can significantly improve the efficiency and allow for much thinner devices. A Lambertian surface, which has the most random texture, can theoretically raise the light path to 4n2 times that of a smooth surface. It´s a challenge however to fabricate ideal Lambertian texture, especially in a fast and low cost way. In this work we have developed a method to overcome this challenge that combines the sue of laser interference lithography (LIL) and selective wet etching. The approach allows for a rapid wafer scale texture processing with subwavelength (nano-) scale control of the pattern and the pitch. The technique appears as being particularly attractive for the development of ultra-thin III-V devices, or in overcoming the weak sub-bandgap absorption in devices incorporating quantum dots or quantum wells. Preliminary results on the application of the technique for sets of patterns relevant to the development of back reflector for 1-1.3 eV MQW solar cells are presented.