As smart electronic products are increasingly applied in our daily life, there is not only an increasing demand for high-performance photovoltaic power generation devices, but also strong need for in-situ energy storage functions in these devices. The integration of energy generating components and energy storage components into one device has become an attractive challenging technology. The basic idea is that by integration design and engineering the assembly of the photoelectric conversion layer and the energy storage layer into one in-situ energy conversion and storage system could not only offer multiple functions, such as self-powered ability, weak light buffer and portability, but reduce sunlight fluctuation effect on energy output. This review summarizes the research progress in novel in-situ integrative photovoltaic-storage tandem cells, classified by silicon solar cell, sensitized solar cell and perovskite solar cell. Evaluation of methodology, operational principle, construction feature, and performance parameter are also discussed and critically reviewed, and the further development of in-situ integrative photovoltaic-storage tandem cell is also prospected.

In thermoelectric (TE) devices, the interfacial reliability greatly influenced devices’ durability and power output. For skutterudites (SKD) devices, TE legs and electrodes are bonded together with diffusion barrier layer (DBL). At elevated temperatures, DBL react with SKD matrix or electrode to generate complex interfacial microstructures, which often accompanies evolutions of the thermal, electrical and mechanical properties at the interfaces. In this work, a finite element model containing the interfacial microstructure characteristics based on the experimental results was built to analyze the interfacial stress state in the skutterudite-based TE joints. A single-layer model was applied to screen out the most important parameters of the coefficient of thermal expansion (CTE) and the modulus of DBL on the first principle stress. The multilayer model considering the interfacial microstructures evolution was built to quantitively simulate the stress state of the TE joints at different aging temperatures and time. The simulation results show that the reactive CoSb₂ layer is the weakest layer in both SKD/Nb and SKD/Zr joints. And by prolonging the aging time, the thickness of the reaction layer continuously increased, leading to a significant raising of the interfacial stress. The tensile testing results of the SKD/Nb joints match the simulation results well, consolidating accuracy and feasibility of this multilayer model. This study provides an important guidance on the design of DBL to improve the TE joints’ mechanical reliability, and a common method to precisely simulate the stress condition in other coating systems.

As a type of environmental benign secondary battery with high power density, Ni-Zn battery is often limited by the weakness of negative electrode materials in the applications. In this work, ZnO nanorods (NRs) with high performance were synthesized by Sol-Gel process with hexamethylenetetramine (HMT) as template and subsequent thermal annealing treatment. Morphology, crystalline structure and surface functional groups of ZnO NRs were characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD) and Fourier-transform infrared spectroscope (FT-IR), respectively. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) measurements reveal that ZnO NRs have carbon layers on the surface and vacancies in the lattice. Tafel tests and electrochemical impedance spectroscopy (EIS) show that the corrosion current and charge transfer resistance of ZnO NRs-based electrodes are reduced by 40% and 62%, respectively, compared with commercial ZnO. Further investigation show that Ni-Zn batteries fabricated with ZnO NRs have better cycling performances. After 100 cycles at a current density of 1 A·g^-1, the capacity retention rate of ZnO NRs is 92%, which is significantly higher than that of commercial ZnO powder (32%).

New intercalated compounds Pd_xNbSe₂ (x=0-0.17) were synthesized via solid-state reaction. They possess the parent structure of 2H-NbSe₂ and crystalize in the hexagonal space group of P6₃/mmc. The intercalated Pd occupies the octahedral position in the van der Waals gaps of 2H-NbSe₂. Unit cell parameter c increases linearly with the Pd content, while a is nearly unchanged. The lattice parameter of Pd_0.17NbSe₂ (a=b=0.34611(2) nm, c= 1.27004(11) nm) is identified by single crystal X-ray diffraction. The intercalated Pd stabilizes the crystal structure of NbSe₂ by connecting the adjacent Nb-Se layers with [PdSe₆] octahedra and leads to the enhanced thermostability in air. Temperature dependence of electric resistivity reveals that the residual resistivity ratio of Pd_xNbSe₂ monotonically decreases with addition of the intercalated Pd content. The decreased superconducting critical temperature of Pd_xNbSe₂ indicates the suppression effect of Pd intercalation on the superconductivity in the host NbSe₂.

La_0.3Y_0.7Ni_3.4-xMn_xAl_0.1(x=0-0.5) hydrogen storage alloys were prepared by vacuum arc melting followed by homogenized annealing. Effect of Mn element on the microstructure, hydrogen storage behavior and electrochemical properties were systematically investigated via different methods. The results show that the microstructure of the annealed alloys closely relates to the Mn content. Higher Mn content facilitates the formation of Ce₂Ni₇ type phase until single phase structure of Ce₂Ni₇- type forms in the alloys with x≥0.3. With the increment of Mn content, the unit cell parameters (a, c) and unit cell volume (V) of Ce₂Ni₇- type phase increase, resulting in the hydrogen absorption platform pressure of the alloys decreasing from 0.079 MPa to 0.017 MPa and the hydrogen storage capacities reaching 1.268wt%-1.367wt%. The electrochemical properties are significantly improved with the addition of Mn. La_0.3Y_0.7Ni_3.25Mn_0.15Al_0.1 alloy exhibits the highest discharge capacity (390.4 mAh·g ^-1). The capacity retention S₁₀₀ of the alloys with x=0.15 and 0.5 are 86.03% and 88.01%, respectively, presenting good cycle stability. Meanwhile, high rate discharge ability (HRD₉₀₀) of the as-prepared alloys is 71.53%-87.73%. It is shown that electrochemical reaction kinetics of the alloy electrodes is controlled by both the electron transfer at the electrode/ solution interface and the diffusion of hydrogen atoms in the alloy bulk.

Wearable sensors which can evaluate the health status of the human body by conveniently monitoring human’s pH of sweat and body temperature have attracted wide attention. Here, sensors for sweat pH and skin temperature monitoring were developed. ZnO/polyaniline (PAni) micro-nano structure which sensitivity reaches 120 mV/pH realized pH sensing by monitoring the change of surface potential in solutions under different pH conditions. A layer of ZnO/rGO on surface of polyethylene glycol terephthalate/indium tin oxid (PET/ITO) was constructed for temperature monitoring by a simple drop-casting method. With the temperature increasing, the resistance of ZnO/rGO composite decreases, and the sensitivity of its resistance variation reaches -0.67%/℃. Two sensors are integrated into one sensor chip which shows high stability. Therefore, the new sensor with practical and commercial potential is promising in the field of pH and temperature detection.