P-Type PbS Quantum Dot Solar Ink via Hydrogen-Bonding Modulated Solvation for High-Efficiency Photovoltaics

Ligand modulation of the electrical properties and surface solvation plays a crucial role in the development of functionalized colloidal quantum dots (CQDs) inks for solution-processed optoelectronics. While inorganic halide ionic ligands can facilitate the n-type doping of PbS CQDs and establish an electrical double layer in polar solvents for stable high-concentration n-type CQD inks, a plausible solvation strategy is still lacking to stabilize p-type PbS CQDs, thereby resulting in a tedious multi-step deposition involving short-chain dithiol molecular ligands for advanced heterojunction CQD solar cells. Here an effective hydrogen bonding solvation strategy is proposed using 2-mercaptoethanol (ME) ligands to realize stable p-type PbS CQD ink. This strategy enables DMSO to form a dense solvation layer surrounding the ME-modified PbS CQDs. With this approach, the PbS-ME CQD ink exhibits a photoluminescence quantum yield of 52.03%, which is the highest record for PbS CQD inks. Finally, one-step deposition of a p-type PbS-ME layer for PbS CQD photovoltaics is successfully achieved with an impressive power conversion efficiency (PCE) of 10.91%. This p-type solar ink facilitates the fabrication of ready-to-use devices, enabling extensive applications in large-scale and flexible optoelectronic devices. The robust hydrogen bonding between the ME ligand and the DMSO solvent facilitates the formation of a compact solvation layer around the PbS-ME CQDs, achieving a stable p-type PbS CQDs solar ink for the direct solution-deposition of CQDs photovoltaics.image