Homogenizing luminescent coupling (LC) effect in multijunction solar cells (MJSCs) was estimated to increase conversion efficiency by 1.35%. The luminescence mapping method was used to observe the LC effect in MJSCs at high carrier injection, in parallel with laser beam induced current (LBIC) mapping. At high MJSC terminal voltage, the luminescence image of the higher bandgap subcell had the same profile as the spatial current collection in the lower bandgap subcell obtained by LBIC mapping. Thus, it may be established that the emission profile of the higher bandgap subcell affects the LC current collection of its adjacent lower bandgap subcell.