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Recently, the inherent piezoelectric properties of the 2D transition-metal dichalcogenides (TMDs) tin monosulfide (SnS) and tin disulfide (SnS2) have attracted much attention. Thus the piezoelectricity of these materials has been theoretically and experimentally investigated for energy-harvesting devices. However, the piezoelectric output performance of the SnS2- or SnS-based 2D thin film piezoelectric nanogenerator (PENG) is still relatively low, and the fabrication process is not suitable for practical applications. Here we report the formation of the SnS2/SnS heterostructure thin film for the enhanced output performance of a PENG using atomic layer deposition (ALD). The piezoelectric response of the heterostructure thin film was increased by ∼40% compared with that of the SnS2thin film, attributed to large band offset induced by the heterojunction formation. Consequently, the output voltage and current density of the heterostructure PENG were 60 mV and 11.4 nA/cm2at 0.6% tensile strain, respectively. In addition, thickness-controllable large-area uniform thin-film deposition viaALD ensures that the reproducible output performance is achieved and that the output density can be lithographically adjusted depending on the applications. Therefore, the SnS2/SnS heterostructure PENG fabricated in this work can be employed to develop a flexible energy-harvesting device or an attachable self-powered sensor for monitoring pulse and human body movement.

In this study, eco-friendly Pb-free Bi2O3--B2O3--ZnO glass frits were chosen as an inorganic additive for the Al paste used in Si solar cells. The effects of the molar ratio of Bi2O3to B2O3in the glass composition on the electrical resistance of the Al electrode and on the cell performance were investigated. The results showed that as the molar ratio of Bi2O3to B2O3increased, the glass transition temperature and softening temperature decreased because of the reduced glass viscosity. In Al screen-printed Si solar cells, as the molar ratio of Bi2O3to B2O3increased, the sheet electrical resistance of the Al electrode decreased and the cell efficiency increased. The uniformity and thickness of the back-surface field was significantly influenced by the glass composition.

The effect of high pressure pure hydrogen annealing (HPHA) on the conversion efficiency of multicrystalline silicon solar cells was investigated at various temperatures and pressures. HPHA led to a better supply of hydrogen near the interface between the Ag electrode and the SiN antireflection layer of a solar cell, resulting in increased cell conversion efficiency. As compared with an as-fabricated sample, the postannealed samples in pure hydrogen ambient under optimum process conditions exhibited the improved cell conversion efficiency by 2% absolute. HPHA is a useful method to enhance the conversion efficiency of low grade multicrystalline silicon solar cells.