Efficient near-infrared PbS QDs superlattice optical amplifier via dual-ligand modulation

Near-infrared (NIR) optical communication has driven research on optimization of photoluminescence quantum yield (PLQY) in PbS colloidal quantum dots (QDs). To improve PLQY of PbS QDs, this study proposed a synergistic modification strategy using oleic acid (OA)-triphenylphosphine (TPP) dual ligands. By passivating surface defects of QDs, this strategy achieves a systematic improvement in the PLQY of PbS QDs. Optical characterization results indicate that compared with oleylamine (OLA)-modified samples, the OA-TPP modification increases the PLQY of PbS QDs by 20%–30%. Additionally, the PLQY of a PbS superlattice fabricated from OA-TPP modified PbS QDs (PbS-OA-TPP QDs) reaches 16%, whereas the PLQY of a PbS QD superlattice prepared using OLA-modified PbS QDs is typically less than 10%. Furthermore, the short interparticle spacing between PbS-OA-TPP QDs in superlattices subjects PL properties to the influence of excitation energy transfer, which shortens the PL lifetime to 66 ns by enhancing the short decay component. NIR optical communication test results show that an optical amplifier based on PbS QD superlattices achieves a −3 dB modulation bandwidth of 2.35 MHz and a maximum transmission rate of 2.4 Mbit/s, verifying the significant potential in optical communication. This study provides a promising approach for optimizing the luminescent performance of PbS QDs towards developing NIR communication devices.