Perovskite solar cells (PSC) are considered promising next generation photovoltaic devices due to their low cost and high-power conversion efficiency (PCE). The perovskite material in the photovoltaic devices plays the fundamental role for the unique performances of PSC. Formamidinium based perovskite materials have become a hot-topic for research due to their excellent characteristics, such as a lower band gap (1.48 V), broader light absorption, and better thermal stability compared to methylammonium based perovskite materials. There are four phases of perovskite materials, named the cubic α-phase, tetragonal β-phase, orthorhombic γ-phase, and δ-phase (yellow). Many research focus on the transition of α-phase and δ-phase. α-Phase FA-based perovskite is very useful for photovoltaic application. However, the phase stability of α-phase FA-based perovskite materials is quite poor. It transforms into its useless δ-phase at room temperature. This instability will lead the degradation of PCE and the other optoelectronic properties. For the practical application of PSC, it is urgent to understand more about the mechanism of this transformation and boost the stability of α-Phase FA-based perovskite materials. This review describes the strategies developed in the past several years, such as mixed cations, anion exchange, dimensions controlling, and surface engineering. These discussions present a perspective on the stability of α-phase of FA-based perovskite materials and the coming challenges in this field.

No abstract

Aqueous zinc-ion hybrid supercapacitors (AZHSs) are promising candidates for powering mobile devices due to their intrinsically high safety, the high theoretical capacity of zinc anodes, and the wide range of sources of raw materials for activated carbon (AC) cathodes. Here, we report that there is a synergistic effect between the anions of an AZHS electrolyte, which can significantly improve the specific capacity and rate capability of an AC cathode. The results showed that the specific capacities of the AC cathode//2 M ZnSO4(aq)//Zn anode energy storage system were 115 and 41 mAh g−1 at 0.1 and 5 A g−1 current densities, respectively. The specific capacity at a 0.1 A g−1 current density was enhanced to 136 mAh g−1 by doping 0.5% ZnCl2 and 0.5% Zn(CF3SO3)2 in the 2 M ZnSO4 electrolyte. The specific capacity at a 5 Ag−1 current density was enhanced to 69 mAh g−1 by doping 1% ZnCl2 and 0.5% Zn(CF3SO3)2 in the 2 M ZnSO4 electrolyte. In addition, the co-doped electrolyte increased the energy consumption of the binding of the AC surface groups with H+ and inhibited the precipitation of Zn4SO4(OH)6·5H2O. This provides an important perspective for improving the performance of AZHSs.

Due to the potential use in the energy storage and next generation of water-purification devices, neutral aqueous supercapacitors (NASC) have attracted significant attention from researchers. MnO2 is the well-known cathode...