Diffusion-controlled bimolecular recombination of electrons and holes in a-Si:H

The fluctuation-dominated and mean-field models for diffusion-controlled bimolecular recombination are compared with picosecond domain transient optical experiments on a-Si:H. Using no fitting parameters, the fluctuation-dominated model gives a good account for the optical decay times as a function of laser intensity. A lower bound for the thermalization radius of a photogenerated electron-hole pair, r0 > 12 nm, is inferred. a-Si:H ia felicitous material for exhibiting the fluctuation-dominated effects since it combines a modest electron mobility with an unexplained but large thermalization radius. However, the role of the electrostatic potential fluctuations due to the charged electrons and holes is not understood.