Core–Shell Cd(S,Se)/ZnS Quantum Dots as Rear-Interface Modifiers for Efficient CdSeTe Thin-Film Solar Cells

Cadmium selenide telluride (CdSeTe) thin-film photovoltaics have achieved remarkable progress in power conversion efficiency and long-term stability, yet back-contact limitations remain a major barrier to reaching their theoretical efficiency. Here, we introduce a low-temperature, solution-processed Cd(S,Se)/ZnS core–shell quantum-dot (QD) rear-interface modifier to address these challenges. The Cd(S,Se) core provides favorable valence-band alignment with the CdSeTe absorber and contributes additional absorption, while the wide-bandgap ZnS shell passivates rear-surface defects and enhances chemical stability. Incorporation of this QD layer enables efficient hole extraction, suppressed nonradiative recombination, and improved device performance, yielding a champion power conversion efficiency of 19.3%, significantly higher than that of control devices. This work establishes a chalcogenide core–shell QD-based interface-engineering strategy that mitigates back-contact recombination and band misalignment, offering a practical pathway to further advance CdSeTe thin-film solar cells in efficiency and durability.