5.2% efficient PbS nanocrystal Schottky solar cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c3ee41479e

The impact of post-synthetic treatments of nanocrystals (NCs) on the performance of Schottky solar cells, where the active PbS nanocrystal layer is sandwiched directly between two electrodes, is investigated. By monitoring the amount of ligands on the surface of the nanocrystals through Fourier Transform Infrared (FTIR) measurements, we find that optimized processing conditions can lead to high current density and thus to an increase in overall efficiency. Our devices reach an efficiency of 5.2%, which is the highest reported using a PbS nanocrystal Schottky junction. These results demonstrate that even by using the simplest device architecture, accurate post-synthetic treatments result in substantial improvements in the performance. By drawing a direct correlation between ligand-to-NC ratio in the starting PbS solution and the device parameters, we provide important insights on how to gain experimental control for the fabrication of efficient PbS solar cells. PbS nanocrystal Schottky junctions with a power conversion efficiency of 5.2% are reported, as a result of a systematic control of the material quality.