Improved conversion efficiency in dye-sensitized solar cells based on porphyrin dyes with dithieno[3,2-b:2′,3′-d]pyrrole donor

Dithieno[3,2-b:2',3'-d]pyrrole (DTP) has proved to be a powerful donor to construct novel D-pi-A type porphyrin sensitizers for highly efficient dye-sensitized solar cells. Compared with the reference dye YD2-o-C8, replacing the diphenylamine donor with modified DTP unit resulted in a promotion of molar absorption coefficient from 2.11 x 10(5) to 3.46 x 10(5) M-1 cm(-1), and endowed dye JY47 good lightharvesting ability. This structural modification led to an enhanced photocurrent (16.54 vs. 15.68 mA cm(-2)) and higher power conversion efficiency (7.95% vs. 7.76%) of JY47 based-device relative to YD2-o-C8 baseddevice with iodine electrolyte under the same conditions. Dye JY48 containing additional electron-withdrawing group benzothiadiazole (BTD) gave the highest PCE of 8.44%, around 1.1 times of that of YD2-o-C8, with a J(sc) of 18.43 mA cm(-2), a V-oc of 717 mV and a FF of 0.64 under AM 1.5 G irradiation. These results demonstrate that dithieno[3,2-b:2',3'-d]pyrrole is a promising donor to constructing highly efficient porphyrin sensitizers, besides acting generally as a pi-spacer in dye-sensitized solar cells (DSSCs).