The effect of quantum dot ligand treatements on polaron lifetime and photovoltaic device performance

Using quasi-steady state photoinduced (PIA) absorption spectroscopy, we demonstrate that treating polymer/PbS quantum dot blend films with ethanedithiol (EDT) shortens average polaron lifetime. Devices fabricated from these films exhibit an improvement of more than 30% to the AM 1.5 power conversion efficiency upon thiol treatment, owing to an increase in photocurrent. These results are consistent with the hypothesis that thiols passivate deeply bound trap states on the surfaces of PbS quantum dots and that surface treatments could further improve bulk hybrid heterojunction solar cell performance.