On Dependence of the Multijunction InGaP/GaAs/Ge, InGaP/GaAs Solar Cell Efficiency on the Sunlight Concentration

Correlation between two main characteristics of multijunction (MJ) solar cells (SC) and their segment character have been studied theoretically and experimentally: the dark voltage - current characteristic and the characteristic corresponding to it: efficiency - concentration ratio, ) ( g J C ∝ − η . The characteristics have been investigated in two steps. At the first step, an idealization has been done, which did not take into account of tunnel p ++ - n ++ junctions, series resistance of the structure, and other elements. The idealized characteristics have the shape of an uninterrupted function comprised of specific segments. For each segment, an analytical formula expressing the generated current through the efficiency has been derived. The formula derivation has been done at the condition of generated current matching (equality of generated currents in photovoltaic junctions of a MJSC). The analytical characteristic segment is set by the same two parameters (preexponential factor J ) ( g J C ∝ − η 0 and diode coefficient A) as of the corresponding dark V - J characteristic segment. Therefore, the performance connectorless characteristic is unambiguously associated with the initial connectorless dark V - J characteristic. At the second step, the effect of the MJSC connecting part has been taken into account, which was simulated by selected ohmic resistance. The connectorless characteristic have been calculated and plotted segment by segment. A good fit between the rated and experimental dependencies have been obtained for dual- junction InGaP/GaAs SCs. A acceptable fit between the calculated and experimental data has been obtained for triple-junction InGaP/GaAs/Ge SCs, in spite of there is no generated current matching. ) ( g J C ∝ − η ) ( g J C ∝ − η ) ( g J C ∝ − η