Effects of donors of bodipy dyes on the performance of dye-sensitized solar cells

A new series of donor-acceptor-pi-linker-acceptor (D-A-pi-A) featured organic dyes containing Bodipy derivative as the auxiliary acceptor, furan unit as the pi conjugated spacer, and 2-cyanoacrylic acid as the anchor group were synthesized and applied in dye-sensitized solar cells (DSSCs). The incorporated electron-withdrawing unit of Bodipy enhances light harvesting by decreasing the molecular energy gap and red-shifting absorption spectra. For comparison, three different arylamine chromophores namely 3-methoxy-9H-carbazole (CBZ-B), triphenylamine (TPA-B) and phenoxazine (POZ-B) were separately appended onto the 6-position of Bodipy unit to study the effect of the electron donating groups on device performance. The UV-vis absorption spectra, electrochemical properties, density functional theory calculation, photovoltaic properties and electrochemical impedance measurements of DSSCs with these three dyes were systematically investigated. The Bodipy dyes have broad absorption spectra covering the range of 250-700 nm with the highest molar extinction coefficient up to >55 000 M-1 cm(-1). The molecular energy level tuning can be conveniently accomplished by alternating the donor moiety. The DSSCs based on TPA-B showed the best photovoltaic performance: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 70%, a short-circuit photocurrent density (J(sc)) of 13.95 mA cm(-2), an open-circuit photovoltage (V-oc) of 557 mV, and a fill factor (ff) of 0.61, corresponding to an overall conversion efficiency of 4.76% under standard global AM 1.5G solar light conditions. Our research demonstrates that Bodipy based D-A-pi-A molecular architecture is a highly promising class for the improvement of the performance of DSSCs in the future. (C) 2017 Elsevier Ltd. All rights reserved.