  The radiative recombination, Shokley-Read recombination, frontal-surface and
rear-surface recombination and the recombination at the heterojunction
boundaries and the recombination in the space charge region are considered in
the calculation of the multijunction solar cell (MSC) efficiency. The
calculation is performed by a self-consistent solution of the equations for the
photocurrent and photovoltage, as well as the heat balance equation. A cooling
of MSC with the increase of the number of cells n and the improvement in the
heat dissipation is regarded. It was found that, as the number of cells n is
increased, narrowing of spectral range for each cell causes additional
reduction of current. A substantial increase in the MSC efficiency can be
achieved by improving the heat extraction using radiators and increasing
emissivity. A comparison is made between the calculated and experimental
efficiency values. A rather good agreement was found. A comparison between this
calculation and other formalisms is given.
