Diagnosis and Breakeven Analysis of GaInNAs Subcell Incorporated in Monolithic Lattice-Matched Five-Junction Solar Cell

Abstract

We focus on the diagnosis and breakeven analysis of the critical dilute nitride subcell incorporated in a monolithic AlGaInP/AlGaInAs/InGaAs/GaInNAs/Ge five-junction (5J) solar cell grown by metalorganic vapor phase epitaxy. Via absolute electroluminescent measurement and with the help of the control cells, some key internal performance of our latest 5J with AM0 efficiency of 28.8% are disclosed, where the subcell <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">oc</sub> from top to bottom are assessed as 1576±1 mV, 1253±4 mV, 1001±1 mV, 372 mV, and 196 mV, respectively. The yield contributed by the top three subcells is assessed as 26.8%, while that by the GaInNAs- and Ge-subcell is only 2.0% in total. The evaluated internal radiative efficiency of the top three subcells reveal that GaInNAs-subcell growth leads to obvious degradation of the lattice quality in the closest GaInAs-subcell and slight drops in the AlGaInP- and AlGaInAs-subcells. Finally, a semiempirical approach is used to predict the essential parameters on the 1-eV subcell used for such 5J architecture so that it can exceed the efficiency benchmark of 30%–34%.