This work reports an investigation of the effect of excitons on carrier recombination and solar energy conversion processes. The probabilities of exciton-stimulated modulation of the occupancy ofrcenters in CdS as well as the binding coefficient of free electrons and holes into excitons are estimated. Carrier recombination and transport theories are presented. The theories are applied toCu2S/CdSsolar cells for AM1 illumination at a temperature of 300 K. It has been shown by numerical estimation that exciton-stimulated modulation of the occupancy of deep impurities does give a significant reduction of carrier recombination losses and efficiency improvements forCu2S/CdSsolar cells. ©1997 American Institute of Physics.