Hydrophobic carbon/Whitlockite derived from expired yogurt as a counter electrode for dye-sensitized solar cell (DSSC)

Abstract

The dye-sensitized solar cells (DSSCs) were assembled using counter electrodes (CEs) constructed of carbonized yogurt/PEDOT:PSS composites and evaluated for their efficiency. The influences of two different crucible materials used during the pyrolysis of hydrothermally treated nonfat yogurt on the structures and properties of derived carbons were compared. Carbons denoted by Aa and Ab were pyrolyzed on an aluminum alloy boat and an alumina one, respectively. Hydrophobic carbon/nano-Whitlockite (WH) composites were obtained for both crucible materials. The carbon features are primarily made up of nanocarbons, micronized carbon spheres, and carbyne nanowires. Aa and Ab have surface areas (SBET) of 1060 and 289.7 m2 g−1, respectively. Moreover, the Aa carbon has a lower degree of oxidation than the Ab sample. The electrocatalytic activity of Aa carbon is higher than that of Ab carbon but Aa is less hydrophobic than Ab. Whitelockites were also prepared from hydrothermal synthesis and oxidation of Aa and Ab samples. Notably, the electrocatalytic activities of Whitlockites/PEDOT:PSS are as good as that of Pt but it is still lower than Aa/PEDOT:PSS and Ab/PEDOT:PSS electrodes. The DSSC with an Aa/PEDOT:PSS CE has a slightly higher efficiency (7.40%) than the DSSC with an Ab/PEDOT:PSS CE (7.05%) and the one with a Pt CE (7.01%) because Aa DSSC has a slightly higher fill factor (FF) and short-circuit current density (Jsc). Note that the Whitelockites/PEDOT: PSS can not be used as counter electrodes since these films swell excessively, resulting in a short circuit. Carbon in Aa and Ab plays a very important role in preventing such swelling incidence.