  The coagulation of dust particles under the conditions in protoplanetary
disks is investigated. The study focuses on the repulsive electrostatic barrier
against growth of charged dust grains. Taking into account the photoelectric
effect leads to the appearance of a layer at intermediate heights where the
dust has a close to zero charge, enabling the dust grains to grow efficiently.
An increase in the coagulation rate comes about not only due to the lowering of
the Coulomb barrier, but also because of the electrostatic attraction between
grains of opposite charge due to the non-zero dispersion of the near-zero
charge. Depending on the efficiency of mixing in the disk, the acceleration of
the evolution of the dust in this layer could be important, both in the
quasi-stationary stage of the disk evolution and during its dispersal.
