Recombination and photoconductivity in amorphous semiconductors at low temperatures

The problem of simultaneous hopping diffusion and recombination of electron-hole pairs, photoexcited in non-crystalline semiconductors at low temperatures, is reduced to a universal geometrical problem whose solution does not depend on the density of states function. The distribution of radiative recombination times after pulse excitation is found. A theory of steady state carrier concentration and of the dc and ac photoconductivity is presented.