Push–pull porphyrins with different anchoring group orientations for fully printable monolithic dye-sensitized solar cells with mesoscopic carbon counter electrodes

Abstract

Here, four D–π–A porphyrin dye molecules with carboxylic acid at the para-position or meta-position of the benzene ring (coded as WH-C4, WH-C1, WH-C6 and WH-C7, respectively) were designed and synthesized for monolithic dye-sensitized solar cells with mesoscopic carbon counter electrodes. Significant optical and electrochemical differences were found for WH-C6 and WH-C7 with carboxylic acid at the meta-position of the benzene ring in comparison with WH-C4 and WH-C1 with carboxylic acid at the para-position of the benzene ring. The influence of anchoring group positions on the photovoltaic performance of corresponding devices was systematically investigated. The devices sensitized by WH-C6 and WH-C7 show inferior open circuit voltage (V_oc) and short circuit photocurrent (J_sc) compared with those sensitized by WH-C4 and WH-C1. The above performance differences were confirmed and explained by electrochemical impedance spectroscopy (EIS), UV-visible absorption spectra and dye loading measurement, respectively.