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

Abstract 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.