Because it is able to produce desalinated water directly using solar energy with minimum carbon footprint, solar steam generation and desalination is considered one of the most important technologies to address the increasingly pressing global water scarcity. Despite tremendous progress in the past few years, efficient solar steam generation and desalination can only be achieved for rather limited water quantity with the assistance of concentrators and thermal insulation, not feasible for large-scale applications. The fundamental paradox is that the conventional design of direct absorber−bulk water contact ensures efficient energy transfer and water supply but also has intrinsic thermal loss through bulk water. Here, enabled by a confined 2D water path, we report an efficient (80% under one-sun illumination) and effective (four orders salinity decrement) solar desalination device. More strikingly, because of minimized heat loss, high efficiency of solar desalination is independent of the water quantity and can be maintained without thermal insulation of the container. A foldable graphene oxide film, fabricated by a scalable process, serves as efficient solar absorbers (>94%), vapor channels, and thermal insulators. With unique structure designs fabricated by scalable processes and high and stable efficiency achieved under normal solar illumination independent of water quantity without any supporting systems, our device represents a concrete step for solar desalination to emerge as a complementary portable and personalized clean water solution.graphene oxide | solar steam | 2D water path | solar desalination | heat localization A s water scarcity (1, 2) becomes one of most pressing global challenges of our time, efficient solar desalination could provide a promising solution to produce clean water directly out of solar energy without extra energy input, particularly urgent for developing countries and remote areas without basic infrastructures (3-5). With rapid development in the past few years (6-16), it is clear that there are two key elements to enable efficient solar desalination: broadband and efficient solar absorption and localized heat management for efficient vapor generation with minimized parasitic thermal loss. So far, significant progress has been made on both of these fronts. Absorbers with various rational designs have been demonstrated with efficient solar absorption (11,14,15). Also, from dispersed particles (6, 7, 16), to porous carbon film (8, 9), to thin metallic absorbers (10,11,14,15), there is a clear trend to confine the absorbed energy in a thinner region for localized heating and more-efficient vapor generation, to minimize dissipated heat to the environment and bulk water. Impressive high-energy transfer efficiency has been achieved, but only for a limited amount of solution, with the assistance of both concentrators and thermal insulation.Efficient and effective solar desalination independent of water quantity under normal one-sun illumination without extra supporting systems will fund...

Tin fluoride (SnF2) is widely used as an effective additive for lead‐free tin‐based perovskite solar cells. However, the function of SnF2 and the mechanism in improving the film morphology are still not clear. In this work, it is clearly demonstrated that SnF2 can play a crucial role in the crystal nucleation process. Due to the limited solubility, SnF2 creates more nucleuses for the crystal growth and therefore enables more uniform thin film with high coverage. It is confirmed that this mechanism can be applied to the growth of both thin film and single crystal. As a result of tin‐fluoride‐assisted heterogeneous nucleation, an MASnIBr2‐based perovskite solar cell with a high and stable power conversion efficiency of 3.70% is demonstrated.

Plasmonic nanostructures have been widely applied in various types of solar cells for improving light absorption and therefore energy conversion efficiency. In this work, we demonstrate that Au@SiO2 core-shell nanorods with finely tuned aspect ratios are highly beneficial for the CH3NH3PbI3 perovskite solar cell, with the simultaneous enhancement of solar absorption and external quantum efficiency across a broad range of wavelength, which can contribute to the increased cross-sectional scattering and spectrally absorbing energy density. Therefore, a 16.1% improvement (from 12.4% to 14.4%) of the maximal external quantum efficiency can be achieved by such structures, accompanied with a 13.5% improvement (from 20.0 to 22.7 mA/cm2) of the maximal short-circuit current density and little improvement of the open-circuit voltage and fill factor. Our findings also provide a general guideline to design solar cell structures with thinner absorber layers and improve the absorption in other poorly light-absorbing devices like lead free perovskite solar cells as well.

As perovskite solar cells show tremendous potential for widespread applications, we find that adding inorganic thermal-stable cesium ions into MAPbI 3 results in significantly improves thermal stability. For un-encapsulated perovskite devices, the energy conversion efficiency maintains about 75% of its original value (over 15%) in the MA 0.85 Cs 0.05 PbI 3 device under 80 min of heating at 140°C in a dry atmosphere (RH ≤ 30%). With significantly improved thermal stability achieved by a convenient process, it is expected that this type of mixed-cation perovskites can further facilitate large scale applications.

No abstract