[en] Well-crystallized Cu₂ZnSnS₄ (CZTS) nanoparticles contain ultrasmall nanocrystals (~ 10 nm) have been grown directly on three-dimensional (3D) transparent porous reduced graphene oxide (rGO) thin films by a facile and scalable solution-based strategy. Few-layer rGO prepared by modified Hummers’ method was used to fabricate hierarchical ultraporous 3D rGO thin films (3DGTFs) with high transmittance (> 75% for 200-nm thick). Single-phase kesterite CZTS nanocrystalline particles were grown uniformly on the surface active sites within the 3D rGO network by hydrothermal method. The as-prepared CZTS/rGO composite thin films exhibited excellent electrocatalytic ability by taking advantages of the high conductivity and high surface area of 3DGTFs and the high catalytic activity of CZTS nanoparticles. As expected, the composite thin films demonstrate more than one order of magnitude lower in electrical resistivity and in charge transfer resistance than the individual CZTS thin films. The conversion efficiency of dye-sensitized solar cells using CZTS/rGO thin films as the counter electrode (CE) approached 6.12%, comparable to that using Pt CE (6.45%) and superior to those using individual CZTS CE (1.07%) and rGO CE (0.18%).

[en] This paper aims at developing an elementary theory of two-dimensional (2D) parameter-induced stochastic resonance (PSR) to contribute to nonlinear image processing. In order to tackle the application of SR in image processing, where adding noise may not be an easy task, we propose to generalize the concept of PSR from the one-dimensional (1D) case to the 2D case. An interesting feature of this paper is that a rigorous analytical framework is developed based on the Fokker-Planck equation (FPE). Some applications to image processing are performed to demonstrate the effectiveness of the approaches based on the proposed theory of 2D PSR. It is believed that the PSR-based methodology as advocated in this paper provides a different, but promising perspective for applying SR techniques to nonlinear image processing