Highly transparent nickel and iron sulfide on nitrogen-doped carbon films as counter electrodes for bifacial quantum dot sensitized solar cells

Abstract

Semiconductors are widely used as counter electrodes in quantum dot-sensitized solar cells. However, many counter electrode materials have poor conductivity and require tedious post-treatment procedures. Here, our groups develop a highly transparent MS2@N-doped C film materials (M = Ni, Fe) derived from layer-by-layer self-assembly of a M-TCPP film as a counter electrode in bifacial CdS/CdSe quantum dot-sensitized solar cells. Devices based on the MS2@N-doped C films exhibited higher respective front- and reverse-side power conversion efficiencies (i.e., 4.57% and 3.98% for the NiS2@N-doped C film and 3.18% and 2.63% for the FeS2@N-doped C film) than those of Pt-based devices (2.39% and 1.74%). We attribute the outstanding catalytic activity and excellent stability of the MS2@N-doped C film materials to the homogeneous sulfides within the transparent nitrogen-doped C film, as confirmed by electrochemical analyses, including cycle voltammetry, impedance spectroscopy and Tafel-polarization measurements.