Ca-doped CuS/graphene sheet nanocomposite as a highly catalytic counter electrode for improving quantum dot-sensitized solar cell performance

Abstract

Copper sulfide (CuS) is one of the most important counter electrodes (CEs) in high-efficiency, quantum dot-sensitized solar cells (QDSSCs). In this work, we investigated the effect of Mg, Ca, Sr and Ba ion incorporation into the CuS layer on the photovoltaic performance of quantum dot-sensitized solar cells. Metal ion-doped CuS was deposited by the successive ionic layer adsorption and reaction (SILAR) method on the FTO substrate. As a result, the quantum dot photoanode with the optimized Ca-doped CuS CE exhibited power conversion efficiency (PCE) of 2.33%, which is much higher than bare CuS CE (PCE 1.68%), Ba-doped CuS (1.81%), Mg-doped CuS (1.82%) and Sr-doped CuS (1.67%). A sandwiched structural Ca-doped CuS/graphen sheet (Ca-doped CuS/GS) electrode was prepared by repeating electrophoretic deposition (EPD) of graphene sheets and deposition of Ca-doped CuS nanoparticles. When a Ca-doped CuS/graphene sheet (Ca-doped CuS/GS) was used as a CE, the QDSSC exhibited higher power conversion efficiency (2.73%) compared to cells with Ca-doped CuS (2.33%) and bare-CuS (1.68%) cathodes. A full description of reasons for efficiency enhancement are discussed in this paper by using diverse electrochemical and spectral analyses.