Synthesis of a dibenzo-BODIPY-incorporating phenothiazine dye as a panchromatic sensitizer for dye-sensitized solar cellsElectronic supplementary information (ESI) available. See DOI: 10.1039/c7nj01735a

• Main Authors: Erten-Ela, Sule, Ueno, Yoshihide, Asaba, Takuro, Kubo, Yuji
• Format: Article
• Language: English
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c7nj01735a

For the application of metal-free organic sensitizers in dye-sensitized solar cells (DSSCs), a boron dibenzopyrromethene (dibenzo-BODIPY)-conjugated phenothiazine dye with cyanoacrylic acid as an anchoring group 1 was synthesized and characterized. It showed an intense absorption band at 638 nm as the λ max value and a molar extinction coefficient ( ) of 1.23 × 10 5 M −1 cm −1 . In addition, a relatively small but significant peak was observed at 440 nm ( = 1.80 × 10 4 M −1 cm −1 ). Such panchromatic features allowed the fabrication of a DSSC with an excellent short-circuit current density ( J sc ) of 19.09 mA cm −2 under 100 mW cm −2 AM1.5G simulated light. The corresponding external quantum efficiency (EQE) indicated that the cell converted the light to a photocurrent in a wide wavelength region up to 780 nm, resulting in a power conversion efficiency (PCE; η ) of 7.69% in an I − /I 3 − redox couple electrolyte without the addition of any coadsorbents. When compared to the control cell loaded with a cycanoacrylic acid-appended phenothiazine 2 , the PCE value of the 1 -loaded cell was 1.5 times larger than that of the control cell because of significant enhancements in both J sc and open-circuit voltage ( V oc ). Electrochemical impedance analysis (EIS) suggested attenuation of the charge recombination when using 1 as a sensitizer. In this way, the 1 -loaded cell showed relatively good DSSC properties comparable to those of the cell with N719 ( η = 7.15%) under the same conditions. The introduction of dibenzo-BODIPY into a phenothiazine dye led to the production of a panchromatic sensitizer for dye-sensitized solar cells, a cell with the dye showing a PCE ( η ) value of 7.69%.