Study of simulations of double graded InGaN solar cell structures

Abstract

The performances of various configurations of InGaN solar cells are compared using nextnano semiconductor simulation software. Here, we compare a flat base-graded wall GaN/InGaN structure, with an In xGa1− xN well with sharp GaN contact layers, and an In xGa1− xN structure with In xGa1− xN contact layers, i.e., a homojunction. The doping in the graded structures is the result of polarization doping at each edge (10 nm from each side) due to the compositional grading, while the well structures and homojunctions are impurities doped at each edge (10 nm from each side) at levels equal to the polarization doping density in the graded structure with similar maximum indium concentration. The solar cells are characterized by their open-circuit voltage, Voc, short circuit current, Isc, solar efficiency, η, and energy band diagram. The results indicate that an increase in Isc and η results from increasing both the fixed and maximum indium compositions, while the Voc decreases. The maximum efficiency is obtained for the InGaN well with 60% In.