Numerical Study of (0001) Face GaN/InGaN p-i-n Solar Cell With Compositional Grading Configuration

The advantages of a (0001) face GaN/InGaN p-i-n solar cell with compositional grading configuration between i-InGaN/p-GaN layers are studied numerically. With the use of the grading layer, the conversion efficiency is markedly promoted due to the reduction of potential barrier height for holes and due to the decrease of polarization. Optimized conversion efficiency is obtained when the thickness of the grading layer increases to a critical value. This critical thickness is strongly influenced by the polarization charges and doping concentration of the grading layer. When the density of the polarization charges is high or the doping concentration is low, a thick grading layer is required to achieve high efficiency.