Finely Interpenetrating Bulk Heterojunction Structure for Lead Sulfide Colloidal Quantum Dot Solar Cells by Convective Assembly

Lead chalcogenides colloidal quantum dot (PbS CQD) solar cells employing an ordered bulk heterojunction (OBHJ) structure allow sufficient utilization of solar energy and at the same time ensure efficient charge extractions. However, the interfacial deficiency was determined to be a significant limiting factor for the further improvement of efficiency. Herein, a finely interpenetrating OBHJ structure between zinc oxide nanowire (ZnO NW) arrays and PbS CQDs was achieved by simultaneously controlling the growth orientation of ZnO NWs and introducing convective assembly as the CQD deposition technique. The inherent directionality during the assembly process leads to dense packing and efficient infiltration of CQDs, forming a valid OBHJ structure. Additionally, a self-assembled monolayer was introduced to further improve the Voc deficit. As a result, a record PCE of 9.92% has been demonstrated for OBHJ structured CQD solar cells that are compatible with low-temperature and scalable manufacturing processes.