High-voltage InGaAs quantum well devices are shown to operate in a regime of suppressed radiative recombination. A novel extended heterojunction structure is employed to reduce non-radiative recombination and expose the limiting n=1 component of the diode current. Short circuit current versus open circuit voltage curves derived from illuminated current-voltage measurements on several sets of InGaAs quantum well solar cells are analyzed, and the underlying saturation current densities extracted. Diode currents lower than those expected from detailed balance theory are observed, and possible mechanisms for the apparent suppression in radiative recombination are discussed.