Packing State Management to Realize Dense and Semiconducting Lead Sulfide Nanocrystals Film via a Single-Step Deposition

The long alkyl ligands on nanocrystal (NC) surfaces must be exchanged with short ligands to render NC films semiconducting for optoelectronic applications. It has become the consensus that through this process, it is unavoidable that detrimental cracks are induced due to the ligand volume loss. In this work, we demonstrate an advanced solid-state ligand exchange strategy to achieve crack-free PbS NC film in a single deposition step, through managing NC packing state and appropriate processing solvent selection. This strategy exhibits remarkable versatility for films with various thicknesses (up to 1 mu m), substrates, and areas, The quality of the NC film is confirmed by solar cells as a representative application. The photovoltaic performance is on par with the reported state-of-the-art PbS NC solar cells. Our approach possesses the advantages of simplicity, "greener" processing, and lower materials costs, showing potential as a facile and reliable way to produce high-quality NC films for practical optoelectronic applications.