Dual Ligand Capped Quantum Dots Improving Loading Amount for High-Efficiency Quantum Dot-Sensitized Solar Cells

In quantum dot sensitized solar cells (QDSCs), high loading of high-quality QD sensitizers is a prerequisite for high photovoltaic performance. Herein, a facile and effective ligand design strategy to improve both the loading amount and optoelectronic performance of QD sensitizers is developed by decorating the QD surface with dual ligands of mercaptopropionic acid (MPA) and inorganic ligands (ILs). Experimental results demonstrate that the coexistence of ILs with MPA can not only reduce solvation energy that facilitates QD loading but also serve as effective cross-linkers for the reduction of interdot repulsion and formation of dense QD layers. Furthermore, various ILs, represented by pseudohalide SCN–, exhibit a great passivation effect on QD surfaces and suppress the defect trap states. Due to these benefits, Zn–Cu–In–S–Se (ZCISSe) QDSCs based on dual SCN/MPA ligands deliver a certified efficiency of 16.10%, which is a new record efficiency for liquid-junction QD solar cells.