Two efficient dye-sensitized solar cells have been fabricated by two novel D-D-pi-A phenothiazine-based organic dyes (PH2 and PH3) with an encapsulated insulated molecular wire (EIMW) as an auxiliary donor. The cell sensitized by PH2 with EIMW as an auxiliary donor shows a much higher photovoltage (V-oc) relative to the reference dye PH1 without EIMW, because the former dye can inhibit dye aggregation and suppress the charge recombination effectively. The results show that the cell sensitized by PH2 with co-adsorption of chenodeoxycholic acid obtains a high power conversion efficiency, even higher than that of the cell based on N719. Thus, an effective way to increase the photovoltage and efficiency of the DSSCs has been developed by introducing the EIMW into the organic dyes due to the effective inhibition of dye aggregation and charge recombination. (C) 2019 Elsevier Ltd. All rights reserved.