  In this paper we report the first measurements of carrier mobilities in an
inorganic nanocrystal: conducting polymer composite. The composite material in
question (lead sulphide nanocrystals in the conducting polymer MEH-PPV was made
using a new single-pot, surfactant-free synthesis. Mobilties were measured
using time of flight (ToF) and steady-state techniques. We have found that the
inclusion of PbS nanocrystals in MEH-PPV both balances and markedly increases
the hole and electron mobilities - the hole mobility is increased by a factor
of ~105 and the electron mobility increased by ~107 under an applied bias of
5kVcm-1. These results explain why dramatic improvements in electrical
conductivity and photovoltaic performance are seen in devices fabricated from
these composites.
