Monolayer Perovskite Bridges Enable Strong Quantum Dot Coupling for Efficient Solar Cells

Solution-processed colloidal quantum dots (CQDs) are promising photoelectronic materials for next-generation photovoltaic devices; however, efficient charge transport and surface passivation have yet to be successfully combined in CQD solids. Here, we report a new CQD surface engineering strategy that enables the growth of a monolayer of perovskite that bridges neighboring CQDs, breaking this limitation. The monolayer of perovskite increases interdot coupling, reducing the distance over which carriers must tunnel. The new CQD solids provide fully a 3-fold improvement in mobility relative to the best prior well-passivated CQD solids. As a result, we report a power conversion efficiency (PCE) of 13.8%, a record among PbS CQD solar cells. The study offers an avenue to high-quality semiconducting nanocrystal solids for CQD applications including photodetectors, tandem cells, and light-emitting diodes.