Interaction of singlet excitons in organic materials with an absorbing surface

It is shown both experimentally and theoretically that the fluorescence of an anthracene crystal is strongly quenched if the crystal is excited close to a metal layer. The fluorescence is reduced by a factor of two if the penetration depth of the exciting radiation is equal to the diffusion length of singlet excitons. This is caused by energy transfer taking place across distances of 10 to 30 Å. The experimental values for the energy‐transfer parameters are in agreement with a theoretical estimate assuming a metal absorption index of about one. This energy‐transfer process also influences the fluorescence decay time. Its significance for the probability of exciton induced electron ejection from the crystal into a metallic or non‐metallic electrode is discussed.