Polymer:nanocrystal hybrid solar cells are receiving renewed attention because of the potential they offer in combining beneficial properties of both the organic and inorganic phases for low-cost, flexible photovoltaics. Lead chalcogenide nanocrystals as the acceptor phase possess advantages of near infrared absorption, large Bohr exciton radii, and high dielectric constants; however, compared to the extensively studied colloidal lead chalcogenide quantum dot solar cells, hybrid solar cells fabricated from blends of organic polymers and lead chalcogenide nanocrystals have been far less successful. Up to now, all successful examples of polymer:lead chalcogenide nanocrystal-based hybrid solar cells mandate post-deposition, thin film chemical treatments to remove long chain, insulating organic ligands from the nanocrystal surface, which is a kinetically limited process. Moreover, no atomically passivated nanocrystals have been utilized in hybrid solar cells, even though halide-passivated PbS nanocrystals hold the record efficiency in colloidal PbS quantum dots solar cells. Herein, a colloidal ligand exchange process for PbS nanocrystals using iodide ligands is reported, followed by a thorough characterization of the resulting surface chemistry. These iodide-passivated colloidal PbS nanocrystals allow for a one-step deposition of high-quality polymer:PbS nanocrystal bulk heterojunction films compared to the post-deposition chemical treatments. From this work, we have gained insight into nanocrystal ligand engineering approaches for optimizing the organic-inorganic interface in hybrid solar cells with atomic ligands, leading to improved power conversion efficiency in these systems.

Iodide-passivated colloidal PbS nanocrystals for application in hybrid solar cells

251st National Meeting (2016)

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