Towards scalable synthesis of high-quality PbS colloidal quantum dots for photovoltaic applications

Accelerating inorganic nanocrystal-based photovoltaic technology needs more efficient synthetic protocols for large scale manufacture, high yield and excellent quality nanocrystal materials. We, for the first time, investigated the highly concentrated synthesis of PbS quantum dots (QDs) and systematically explored their properties and photovoltaic performance. We revealed that the precursor concentration can be scaled up from 0.079 M to 15.8 M (200-fold) while excellent nanocrystal quality is maintained. We found that the size, size distribution, optical properties, and composition of the PbS QDs synthesized with various concentrations show negligible difference. As a result, all the solar cells based on these PbS QDs show excellent performance with stable efficiency in the range of 10% to 10.5%. And the results from carrier recombination, trap density and carrier concentration measurements are consistent with the corresponding photovoltaic performance. More importantly, we proved that the highly concentrated synthesis is a general approach that can be applied to different lead precursors. Thus our approach can successfully provide large-scale production of high quality PbS QDs, providing insights into future large-scale manufacturing of QD solar cells.