Synthesis of new dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units for photovoltaic cells

• Three new dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units were synthesized.
• The effects of substituent on DTP are apparent.
• The truxene-substituted DTP is a promising candidate for photovoltaic cells.

Three new dithieno[3,2-b:2′,3′-d]pyrrole units (DTPA1–3) based on the truxene core have been designed and synthesized for a potential application in photovoltaic cells. One of these units (DTPA1) has been employed to construct a new organic dye (M47), exhibiting a higher solar-to-electrical energy conversion efficiency when compared to reference dyes (M48 and M49) under the same conditions. Absorption spectra, electrochemical cyclic voltammetry, theoretical calculations, current voltage curves and controlled intensity modulated photovoltage spectroscopy have been investigated. M47 sensitized solar cells employing a cobalt electrolyte afford a short circuit photocurrent of 12.1 mA cm−2, an open circuit voltage of 758 mV, and a fill factor of 0.56, corresponding to an overall power conversion efficiency of 5.1% under standard AM 1.5 sunlight. These results suggest that the truxene-substituted dithieno[3,2-b:2′,3′-d]pyrrole derivatives are promising candidates for photovoltaic cells.

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