Numerical investigation of a hybrid-connection four-junction solar cell structure based on detailed balance calculation

Abstract

On the basis of the detailed balance limit model, we calculated limiting efficiency, optimum bandgap energy combination, current density–voltage (J–V) characteristics, and theoretical efficiency for the candidate combination of materials GaInN/GaInP/Ga(In)As/Ge and the thermalization loss of a hybrid-connection four-junction (HC4J) solar cell structure to investigate its theoretical characteristics. Instead of the three-tunnel junctions and series-connection between subcells in a conventional four-junction solar cell, HC4J has two tunnel junctions only, with one junction having been replaced by a transparent electrode. The transparent electrode connects the topmost subcells with the top subcell. The theoretical optimum bandgap combination and the limiting efficiency of HC4J are 3.19/1.77/1.19/0.70 eV and 52.1 %, respectively. To assess the feasibility of the structure, theoretical J–V characteristics were evaluated for GaInN/GaInP/Ga(In)As/Ge with associated bandgap energies 3.20/1.87/1.22/0.7 eV. The open-circuit voltage and short-circuit current were 2.87 V and 17.18 mA/cm2, respectively. Thermalization loss was also calculated for the candidate materials .