Conversion efficiency enhancement of GaN/In_0.11Ga_0.89N solar cells with nano patterned sapphire and biomimetic surface antireflection process

In this study, p-i-n double-heterojunction GaN/In_0.11Ga _0.89N solar cells grown by metal-organic chemical vapor deposition on pattern sapphire substrate are presented. The solar cell with standard process has a conversion efficiency of 3.1%, which corresponds to a fill factor of 58%, short circuit current density of 2.86 mA/cm² , and open circuit voltage of 1.87 V under AM1.5G illumination. To further improve the conversion efficiency of the GaN/In_0.11Ga_0.89N solar cells, two-dimensional polystyrene nanospheres were deposited and self-organized as mask in the anisotropic inductively coupled plasma reactive ion etching process to form a biomimetic surface roughing texture. The surface morphology of the solar cell shows a periodically hexagonal bead pattern and the beads are formed in a diameter of 160 nm with a period of 250 nm. An increase of 15% in short circuit current density is found, thus improving the conversion efficiency to 3.87%. If we optimize the structure for 180 nm of the height and 375 nm of the period, a 10% gain can be expected when compared to the current structure.