Toward Efficient Carbon-Dots-Based Electron-Extraction Layer Through Surface Charge Engineering.

To overcome the low conductivity and parasitic inherent drawback of polyelectrolyte electron transfer layer (ETL), the polymer-functionalized carbon nanodots (C-dots) are used as ETL in the inverted organic solar cells. The prepared C-dots with high luminescent property can absorb the ultraviolet light and convert them into low-energy photons, which may be harvested by the active layer. Moreover, the light-induced filling and release of local states can suppress the leakage current and facilitate electron extraction of the cathode. Consequently, the champion power conversion efficiency of 9.53% for poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2- b:4,5- b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4- b]thiophenediyl]]:[6,6]-phenyl-C70-butyric acid methyl ester device is achieved. This work presents a new strategy to employ low-cost carbon nanomaterials to facilitate the electron transport and collection of organic photovoltaic devices.