Front Surface Nanotexturing for Increased Optical Generation Rate in GaAs Photovoltaic Devices

Front surface nanotexturing can enhance light trapping in III-V heterostructures, thereby reducing the required photovoltaic device thickness and associated material costs. A 3D optical model for light trapping was developed using finite-difference time-domain simulations. An untextured GaAs single junction device was compared to the same structure with a nanotextured InGaP window layer under 850 nm incident light with power density of 0.225 W/cm2. Various nanotexture widths and spacings were analyzed and square prism and slanted sidewall designs were compared. In all cases, surface texturing enhanced the optical generation rate, which was used as a metric for electrical performance. The optimal generation rate for a 400 nm thick GaAs absorber occurred at a texture width of 0.9 μm with 29° slanted sidewalls, a 60% increase compared to an untextured front surface. These findings demonstrate improved light trapping through front surface nanotexturing, which can therefore enable thin III-V devices with high efficiencies and low material costs.