A wide band gap In0.5(Al0.7Ga0.3)0.5P Back Surface Field layer increases 6% more efficiency in DLAR Dual Junction InGaP solar cell

Abstract

A wider band gap (2.3eV) material In0.5(Al0.7Ga0.3)0.5P based BSF layer lattice matched with both top In0.49Ga0.51P and bottom GaAs cell is found to increase 6% more efficiency than other widely used Al0.7Ga0.3As material under the same cell configuration because of its high photo generation rate. A numerical simulation analysis of these BSF layer in InGaP/GaAs dual-junction solar cell is investigated using TCAD tool Silvaco ATLAS. The cell is modeled using these two BSF materials both for top and bottom cells and compared all their performance parameters. InAlGaP is found to be a better choice for both window and BSF layer. The cell efficiency and EQE is further optimized by varying BSF layer thickness under current matching condition which is achieved with relatively thinner BSF layer of top cell (30nm) and the thicker BSF layer of bottom cell (1000nm). For this optimized cell structure, a maximum conversion efficiency of 36.67 % (1000 suns) are obtained under AM1.5G illumination. The detail photogeneration rates in this optimized DJ solar cell structure with DLAR of Al2O3-TiO2 are also generated and compared.