Role of Interfacial Engineering of "Giant" Core-Shell Quantum Dots

Structural engineering of the shell layer in "giant" core-shell quantum dots (QDs) offers precise control over the spatial carrier separation and other optoelectronic properties by forming a quasi-type-II band alignment. We report the synthesis of highly stable "giant" CdSe-CdS QDs with different CdS shell thicknesses (2.2-4.8 nm) and alloyed PbxCd1-xS interfacial layers at the CdSe-CdS interface. The "giant" core-shell QDs with alloyed interfacial layers show a broader absorption spectrum, faster carrier transfer rate, and higher hole leakage into the shell region, compared to CdSe-CdS QDs with similar size, as confirmed by optical, transient photoluminescence decay measurements and theoretical simulations. As a proof of concept, the as-synthesized "giant" core-alloyed shell QD (denoted as CdSe@CPS-13)-sensitized solar cells (QDSCs) yield a power conversion efficiency (PCE) of 4.15%, which is 77% higher than the PCE of QDSCs based on "giant" CdSe-CdS QDs with comparable size and shell thickness. These results show that interfacial engineering is an effective methodology to tailor the optical and electronic properties of core-shell QDs with great potential to enhance the performance of photovoltaic and other solar-energy-driven devices.