Core–Shell Nanophosphor Architecture: Toward Efficient Energy Transport in Inorganic/Organic Hybrid Solar Cells

In this work, a core–shell nanostructure of samarium phosphates encapsulated into a Eu³⁺-doped silica shell has been successfully fabricated, which has been confirmed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution TEM. Moreover, we report the energy transfer process from the Sm³⁺ to emitters Eu³⁺ that widens the light absorption range of the hybrid solar cells (HSCs) and the strong enhancement of the electron-transport of TiO₂/poly­(3-hexylthiophene) (P3HT) bulk heterojunction (BHJ) HSCs by introducing the unique core–shell nanoarchitecture. Furthermore, by applying femtosecond transient absorption spectroscopy, we successfully obtain the electron transport lifetimes of BHJ systems with or without incorporating the core–shell nanophosphors (NPs). Concrete evidence has been provided that the doping of core–shell NPs improves the efficiency of electron transfers from donor to acceptor, but the hole transport almost remains unchanged. In particular, the hot electron transfer lifetime was shortened from 30.2 to 16.7 ps, i.e., more than 44% faster than pure TiO₂ acceptor. Consequently, a notable power conversion efficiency of 3.30% for SmPO₄@Eu³⁺:SiO₂ blended TiO₂/P3HT HSCs is achieved at 5 wt % as compared to 1.98% of pure TiO₂/P3HT HSCs. This work indicates that the core–shell NPs can efficiently broaden the absorption region, facilitate electron-transport of BHJ, and enhance photovoltaic performance of inorganic/organic HSCs

Top-down Strategy toward Versatile Graphene Quantum Dots for Organic/Inorganic Hybrid Solar Cells

Metal oxide nanocrystals have been pursued for various applications in photovoltaics as a buffer layer. However, it remains a challenging task to adjust their energy levels to achieve a better match of the donor–acceptor system. Herein, we report the fabrication of graphene quantum dots (GQDs) with bright blue photoluminescence by a top-down strategy based on laser fragmentation with posthydrothermal treatment. The GQDs demonstrate appropriate energy level positions and are used as an intermediate buffer layer between TiO₂ and P3HT to form a cascade energy level architecture. The introduction of the GQDs into a bulk heterojunction hybrid solar cell has led to an enhancement of the power conversion efficiency