Boosting the efficiency of AgInSe2 quantum dot sensitized solar cells via core/shell/shell architecture

Interfacial engineering of the photoanode has been one of the most important strategies in designing high-performance quantum dot (QD)-sensitized solar cells (QDSSCs). In this work, we demonstrated a promising route to enhance the photovoltaic performance by inserting an additional CdS inner shell between AgInSe2 (AISe) QDs and a ZnS outer shell to obtain an AISe/CdS/ZnS core/shell/shell QDSSC. These double passivation shells prevent current leakage from the QDs to the electrolyte. The results of electrochemical impedance spectroscopy confirmed that the CdS/ZnS double passivation shell in the AISe QDSSC contributes greatly to suppression of charge recombination. As a result, the AISe QDSSC with CdS/ZnS double passivation shells exhibited a remarkably high conversion efficiency (6.27%), which is significantly higher than those of devices without a passivation shell (1.02%) and with CdS (4.37%) or ZnS (5.23%) single passivation shells. To the best of the authors' knowledge, this efficiency is one of the highest values obtained for an Ag-based QDSSC.