Improving Open-circuit Voltage in PbS-based QDPVs Using Different Pb Precursors

Lead sulfide (PbS) quantum dots (QDs) have been researched for photovoltaic (PV) applications for decades. A large open-circuit voltage (V_oc) deficit to bandgap is one of the drawbacks to overcome in PbS QD-based photovoltaics (QDPVs) compared to other photovoltaic systems. Here, we report the V_oc improvement using a different Pb-precursor, PbCl₂, which is known to have an better native ligand for chemical stability and photoluminescence quantum yield. We synthesized appropriate size of PbS QDs for PV applications by the Cademartiri method with modification. The PbCl₂ precursors used in the Cademartiri method supply chloride ions (Cl⁻) for the atomic passivation. The Cl⁻ as a native atomic ligand is substituted to iodide ions (I⁻) through post-synthesis ligand exchange process, and the remaining Cl⁻ as a PbCl_x shell layer still exists after ligand exchange and passivates the QD surface. The V_oc using PbS QDs from the Cademartiri synthesis is 20% larger than that from the Hines synthesis.