Cross-stacked superaligned carbon nanotube (CSCNT) sheets drawn from CNT arrays with excellent conductivity, porosity and flexibility are used as low-cost back contacts for hole conductor-free mesoscopic CH₃NH₃PbI₃/TiO₂ heterojunction perovskite solar cells (PSCs). PSCs integrated with CSCNTs achieve a power conversion efficiency of up to 8.65% and over 10.54% by further doping the CSCNTs with iodine. Moreover, PSCs encapsulated with a layer of polymer poly(methylmethacrylate) exhibit outstanding stability in the dark and under illumination. This work represents a significant step toward the commercialization of the low-cost, stable and high-efficiency hole conductor-free PSCs.

The anechoic coating capable of absorbing sound energy in low frequencies within broadband is essential to conceal underwater vehicles. However, the geometric deformation and modification of mechanical parameters under hydrostatic pressure affect the prediction of absorption performance in deep water environments. An anechoic coating embedded with tandem resonant voids is proposed in this work to achieve quasi-perfect low-frequency and broadband absorption. The analytical method based on the effective medium approach and numerical simulation are performed to estimate the effects of hydrostatic pressure on sound absorption. When additionally considering the dynamic mechanical parameters of the compressed viscoelastic medium, the original absorption humps in low frequencies are inclined to higher band, accompanied by the expanded absorption bandwidth. Then, the tandem coating specimen is measured in a water-filled impedance tube. The experimental spectra are consistent with the analytical and numerical results under various hydrostatic pressures, demonstrating the efficient absorption (α > 0.7) in broadband low frequencies via ordinary pressure. At the same time, the absorption spectrum under higher hydrostatic pressures is also verified in the tube. Consequently, this work paves the way for a broadband low-frequency underwater absorber design and provides an efficient method to characterize the low-frequency and broadband absorption from the coupled resonant coatings in deep water environments.

A dynamic stiffness formulation is developed for both in-plane and bending vibrations of plates with two opposite edges simply supported. The bending motions of plates are described in terms of Leissa’s displacement functions while the in-plane motions take the forms take the forms that were proposed by Bercin and Langley. Using Projection Method, the forces and their corresponding displacements along plate junctions are projected onto a set of orthogonal functions, by which means the well-known spatial dependence difficulties can be overcome, and, as a result, local dynamic stiffness matrix is obtained. Classical finite element technique is utilized to assemble local stiffness matrix into global coordinates. Finally, dynamics of an L-shaped plate is addressed, within which conversion of in-plane and bending motions occurs. Our numerical results are in good agreement with those obtained from finite element method, which demonstrates that this dynamic stiffness formulation has great potential in modeling the dynamics of built-up plate structures, especially in characterizing the in-plane waves, bending waves, and their mutual conversions along plate junctions.

The dynamic stiffness method (DSM) in our recent paper, which can consider both in-plane and out-of-plane vibrations simultaneously, is formulated to investigate the power flow characteristics of built-up plate structures. Prior to power flow analysis, comprehensive validation works on our DSM are performed so as to better exhibit its numerical capabilities. Power input and power transmission within a two-plate structure are then analyzed by following the context of in-plane and out-of-plane vibrations. In addition, three vibration transmission paths within a multiple plate structure are characterized in terms of power flow densities, which can provide better physical insights in vibration transmission within complex plate structures. Compared to power flow analysis based on the well-known reception/mobility method, our approach is strongly recommended for the dynamics of built-up structures since it can assemble the overall stiffness matrix in a straightforward manner like that in the conventional finite element technique.