▎ 摘　　要

Three-dimensional nitrogen doped holey reduced graphene oxide framework (NHGF) with hierarchical porosity structure was developed as high-performance metal-free counter electrodes (CEs) for dye sensitized solar cells (DSSCs). With plenty of exposed active sites, efficient electron and ion transport pathways as well as a high surface hydrophilicity, NHGF-CE exhibits good electrocatalytic performances for I-/I-3(-) redox couple and a low charge transfer resistance (R-ct). The Rct of NHGF-CE is 1.46 Omega cm(2), which is much lower than that of Pt-CE (4.02 Omega cm(2)). The DSSC with NHGF-CE reaches a power conversion efficiency of 5.56% and a fill factor of 65.5%, while those of the DSSC with Pt-CE are only 5.45% and 62.3%, respectively. The achievement of the highly efficient 3D structure presents a potential way to fabricate low-cost and metal-free counter electrodes with excellent performance. (C) 2016 Elsevier B.V. All rights reserved.