Towards efficient photoinduced charge separation in carbon nanodots and TiO₂ composites in the visible region

In this work, photoinduced charge separation behaviors in non-long-chain-molecule-functionalized carbon nanodots (CDs) with visible intrinsic absorption (CDs-V) and TiO₂ composites were investigated. Efficient photoinduced electron injection from CDs-V to TiO₂ with a rate of 8.8 × 10⁸ s⁻¹ and efficiency of 91% was achieved in the CDs-V/TiO₂ composites. The CDs-V/TiO₂ composites exhibited excellent photocatalytic activity under visible light irradiation, superior to pure TiO₂ and the CDs with the main absorption band in the ultraviolet region and TiO₂ composites, which indicated that visible photoinduced electrons and holes in such CDs-V/TiO₂ composites could be effectively separated. The incident photon-to-current conversion efficiency (IPCE) results for the CD-sensitized TiO₂ solar cells also agreed with efficient photoinduced charge separation between CDs-V and the TiO₂ electrode in the visible range. These results demonstrate that non-long-chain-molecule-functionlized CDs with a visible intrinsic absorption band could be appropriate candidates for photosensitizers and offer a new possibility for the development of a well performing CD-based photovoltaic system.