Lead Sulfide Quantum Dot Solar Cells

Size-tunable optical properties and solution processability make quantum dots (QDs) promising candidates to replace traditional photovoltaic (PV) materials as a low cost alternative. Because of their tunable optical properties, air-stability, and relative earth-abundance, PbS QDs are a leading candidate for next-generation solar cells. Here, we optimized synthetic methods and device architectures in order to increase the performance PbS QD based PVs. First, we investigated different PbS QD synthesis methods to assess their size dispersity and scalability. Physical processing techniques such as spin coating and dip-coating, were optimized to provide uniform, defect-free films of optimal thickness. We explored a range of surface ligands, including 3-mercaptoproponic acid (MPA) and lead iodide (PbI), in p-n and p-i-n heterojunction configurations, respectively. A champion device was fabricated with a short circuit current density of 18.14 mA/cm², open circuit voltage of 500 mV, fill factor of 45.7%, and solar-to-electric power conversion efficiency of 4.11%.