Weak Electrostatic Network Structure Improves PbS Quantum Dot Ink Stability

PbS quantum dot (QD) ink stability in polar solvents is critical for high-performance solar cell fabrication. However, QD aggregation in such solvents often leads to epitaxial fusion, resulting in trap states that degrade the device performance. Here, we demonstrate a novel strategy for enhancing ink stability by constructing a weak electrostatic network structure on the QD surface, which is cobuilt by hydrogen bonds and π interactions, providing a stable environment that prevents QD aggregation and epitaxial fusion. The optimized surface structure confers an ink film, with a 13% reduction in Urbach energy, a 50% decrease in trap state density, and a 107% prolongation of carrier lifetime, suggesting significantly enhanced carrier transport and extraction capabilities. With this approach, PbS QD solar cells can achieve a power conversion efficiency of 13% and remain stable for over 1000 h without encapsulation when stored in air.