Poly(amidoamine)
(PAMAM) dendrimers are used to modify
the interface
of metal–semiconductor junctions. The large number of protonated
amines contributes to the formation of a dipole layer, which finally
serves to form electron-selective contacts in silicon heterojunction
solar cells. By modification of the work function of the contacts,
the addition of the PAMAM dendrimer interlayer quenches Fermi level
pinning, thus creating an ohmic contact between the metal and the
semiconductor. This is supported by the observation of a low contact
resistivity of 4.5 mΩ cm2, the shift in work function,
and the n-type behavior of PAMAM dendrimer films on the surface of
crystalline silicon. A silicon heterojunction solar cell containing
the PAMAM dendrimer interlayer is presented, which achieved a power
conversion efficiency of 14.5%, an increase of 8.3% over the reference
device without the dipole interlayer.