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subcells in a conventional four-junction solar cell, HC4J has two tunnel junctions only, with one junction having been replaced by a transparent electrode.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/cm(2), respectively. Thermalization loss was also calculated for the candidate materials.