Electron-hole pair excitation in semiconductors via energy transfer from an external sensitizer

We consider the creation of electron-hole pairs in a semiconductor by energy transfer from an excited molecule near the surface. Direct and indirect band-gap semiconductors are treated explicitly. At large sensitizer-semiconductor separations d, our results are in agreement with previous results in a dielectric continuum limit. At small sensitizer-semiconductor separations we find deviations from the results valid in the large-distance limit. For near-band-edge transfer to direct-gap semiconduc- tors the transfer rate does not follow the 1/d³ dependence as d becomes small. For indirect-gap materials we find that at small separations, indirect transitions may occur without phonon assistance.