In situ synthesis of Ti3C2Tx MXene/CoS nanocomposite as high performance counter electrode materials for quantum dot-sensitized solar cells

Abstract Low electrocatalytic activity and/or high charge transfer resistance of counter electrodes (CEs) in quantum-dot-sensitized solar cells (QDSSCs) are the main reasons for the low photovoltaic performance. Herein, the CoS nanoparticles are anchored on the MXene (Ti3C2Tx) via a simple in-situ hydrothermal reaction process. It is the first attempt to use the MXene/CoS as a highly electrocatalytic CE for QDSSCs. The QDSSCs with a MXene/CoS CE shows a significant enhancement in cell performances and yields a promising power conversion efficiency (PCE) of 8.09% compared with that of the QDSSCs with bare CoS (5.77%) and bare MXene (4.25%) CEs. The significant enhancement of PCE value is mainly attributed to the synergistic effects of the unique layered morphology of conductive MXene nanosheets and its cocatalysis with CoS nanoparticles. The coupling of layered MXene with small CoS nanoparticles (~15 nm) provides abundant catalytic active sites. The improved mesoporous morphology contributes a high specific surface area and fast electron transfer channels for Sx2− reduction. Consequently, the MXene/CoS nanocomposite can be utilized as an effective agent to boost up the photovoltaic performance of QDSSCs.