Carrier Transport in PbS Nanocrystal Conducting Polymer Composites

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.