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Photosensitizer systems play a crucial role in light absorption and charge transfer processes. Designing and selecting dye molecules with exceptional photoelectric features remains a significant scientific challenge in the realm of solar cell research. The paper explores the photovoltaic properties of two D-A'-π-A dyes (CS-70 and CS-72) both individually and after co-sensitization with chlorophyll derivatives, utilizing density functional theory (DFT) and time-dependent density-functional theory (TD-DFT) methods. The monomeric dye molecules share the same donor and conjugated bridge but differ in their auxiliary receptors (benzothiadiazole and naphthobisthiadiazole). Firstly, the study investigates the impact of various auxiliary acceptors on the properties of the dye molecules by analyzing their geometrical structure, frontier molecular orbitals, spectral properties, chemical reaction parameters, intramolecular charge transfer, electron injection, density of projected states, and dye regeneration. A detailed explanation for the superior performance of CS-72 is provided. Furthermore, a solar cell evaluation model was developed for the short circuit current density (Jsc), open circuit voltage (Voc), and photoelectric conversion efficiency (PCE) of the single dye molecule. Subsequently, simulations of the co-sensitized molecules with chlorophyll are performed, focusing on structure, excited state properties and charge transfer, suggesting that co-sensitization enhances spectral properties, light-trapping, and regeneration abilities, and long-range charge transfer between the dye molecules and chlorophyll can be found. The results also demonstrate that the Jsc of the co-sensitized molecules were improved, which facilitates the realization of a higher PCE. This study provides theoretical support for the potential of co-sensitizing dye molecules with chlorophyll to enhance solar cell efficiency, offering valuable insights for the future development of green, cost-effective, and efficient solar cells.

Abstract As the associated gas of tight reservoirs, natural gas is abundant and noncorrosive, which is more suitable for the development of tight oil reservoirs in China. However, the mechanism of gas injection development is unclear, and the gas channeling is serious in tight reservoirs after fracturing. The water-alternating-gas (WAG) flooding is an effective means to delay gas channeling and improve oil recovery. Therefore, it is significant to clarify the mechanism of preventing gas channeling and recovering oil by water-alternation-natural gas (WANG) flooding. The WANG flooding experiments with different water–gas slugs were conducted in non-fracture and fractured tight cores. Besides, the oil distribution of different pore spaces of cores before and after displacement and the main contribution spaces on oil recovery were quantitatively analyzed by using nuclear magnetic resonance and core mercury porosimetry techniques. The results indicate that compared with natural gas flooding, the WANG flooding can retard gas channeling, increase formation energy, and enhance oil recovery by up to 14.1%, especially in fractured cores. Under the resistance of water slugs, the gas was allowed to enter smaller pores and its swept volume was expanded. Oil is mainly stored in mesopores (0.1–1 μm) and small pores (0.01–0.1 μm), accounting for over 90% of the total volume. The oil recovered mainly comes from mesopores, which accounts for over 75% of the total amount. Moreover, the WANG flooding strengthens the recovery of oil in mesopores and macropores (1–10 μm), but it also squeezes oil into small pores and micropores (0.001–0.01 μm).