Preparation of 3D graphene networks and a C dot grafted graphene hybrid by new methods for improving the photovoltaic performance of CdS/CdSe quantum dot sensitized solar cells

Abstract

In this paper, we firstly report the preparation of 3D graphene networks (GNs) by sonication-free liquid-phase exfoliation (LPE) and C dot grafted graphene (CD–G) hybrids. The 3D GNs and CD–G hybrids were incorporated into TiO₂ photoanodes for improving the photovoltaic performance of CdS/CdSe quantum dot sensitized solar cells (QDSSCs) due to their unique structures and excellent conductivities. When the amounts of incorporation are 1.6 wt% for GNs and 2.0 wt% for CD–G, η (photoelectric conversion efficiency) exhibited improvements from 4.04% to 4.37% and 4.69%, respectively. The remarkable improvements in η are predominantly ascribed to the fact that the electron transport from TiO₂ to graphene decreased the probability of recombination of charge carriers and ultimately improved the photoelectric conversion efficiency. For CD–G/TiO₂, the electron transport from C dots to graphene may strengthen the effect. This work demonstrates a possibility of fabricating superior photoanodes for enhancing the performances of QDSSCs by designing graphene nanoarchitectures with unique structures and morphologies as the dopants.