Enhanced infrared photovoltaic efficiency in PbS nanocrystal/semiconducting polymer composites: 600-fold increase in maximum power output via control of the ligand barrier

We report a comparison of photoconductive performance of PbS nanocrystal/polymer composite devices containing either oleic acid-capped or octylamine capped nanocrystals (NCs). The octylamine-capped NCs allow over two orders of magnitude more photocurrent under -1 V bias; they also show an infrared photovoltaic response, while devices using oleic acid-capped NCs do not. Further improvement in the photovoltaic performance of films made with octylamine-capped NCs occurs upon thermally annealing the composite layer at 220 degrees C for 1 h. The procedure leads to a 200-fold increase in short circuit current, a 600-fold increase in maximum power output, and an order of magnitude faster response time. (c) 2005 American Institute of Physics.