Making fully printed perovskite solar cells stable outdoor with inorganic superhydrophobic coating

Outdoor environment including moisture, dust, UV, oxygen and thermal stress(repeated heating-cooling)is devastating to perovskite solar cells(PSCs). Here, we demonstrate a new strategy to make fully printed PSCs stable with maximum power output in outdoor environment by coating them with a porous hydrophobic inorganic layer. After coating, the PSCs can maintain superior stability of more than 150 days of outdoor storage, 240 h of continuous operation at the maximum power output point in ambient air with relative humidity as high as ~80%, and stable operation for more than 10 h under raining condition. ANSYS simulation shows that the thin and porous nature of the inorganic coating layer offers much better heat dissipation than conventional encapsulation methods using glasses attached by photocurable epoxy. A similar thermal expansion coefficient of the inorganic encapsulation material with the solar cell substrate can also prevent it from cracking after repeated heating-cooling cycles. All of these merits resulted from our encapsulation method endow the perovskite solar cells with the real outdoor working capability.

Progress in ceramic materials and structure design toward advanced thermal barrier coatings

Thermal barrier coatings(TBCs)can effectively protect the alloy substrate of hot components in aeroengines or land-based gas turbines by the thermal insulation and corrosion/erosion resistance of the ceramic top coat.However,the continuous pursuit of a higher operating temperature leads to degradation,delamination,and premature failure of the top coat.Both new ceramic materials and new coating structures must be developed to meet the demand for future advanced TBC systems.In this paper,the latest progress of some new ceramic materials is first reviewed.Then,a comprehensive spalling mechanism of the ceramic top coat is summarized to understand the dependence of lifetime on various factors such as oxidation scale growth,ceramic sintering,erosion,and calcium–magnesium–aluminium–silicate(CMAS)molten salt corrosion.Finally,new structural design methods for high-performance TBCs are discussed from the perspectives of lamellar,columnar,and nanostructure inclusions.The latest developments of ceramic top coat will be presented in terms of material selection,structural design,and failure mechanism,and the comprehensive guidance will be provided for the development of next-generation advanced TBCs with higher temperature resistance,better thermal insulation,and longer lifetime.

In-situ synthesis,microstructure,and properties of NbB_(2)-NbC-Al_(2)O_(3)composite coatings by plasma spraying

The high melting point and strong chemical bonding of NbB_(2)pose a great challenge to the preparation of high-density nanostructured NbB_(2)composite coating.Herein,we report a novel,simple,and efficient method to fabricate in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating by plasma spraying Nb_(2)O_(5)–B_(4)C–Al composite powder,aiming at realizing the higher densification and ultra-fine microstructure of NbB_(2)composite coating.The microstructure and properties of in-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating were studied comparatively with ex-situ NbB_(2)–NbC–Al_(2)O_(3)composite coating(plasma spraying NbB_(2)–NbC–Al_(2)O_(3)composite powder).The reaction mechanism of Nb_(2)O_(5)–B_(4)C–Al composite powder in plasma jet was analyzed in detail.The results showed that the in-situ nanostructured NbB_(2)–NbC–Al_(2)O_(3)composite coating presented a lower porosity and superior performance including higher microhardness,toughness and wear resistance compared to the plasma sprayed ex-situ NbB_(2)–NbC–Al_(2)O_(3)coating and other boride composite coatings.Densification of the in-situ NbB_(2)–NbC–Al_(2)O_(3)coating was attributed to the low melting point of Nb_(2)O_(5)–B_(4)C–Al composite powder and the exothermic effect of in-situ reaction.The superior performance was ascribed to the density improvement and the strengthening and toughening effect of the nanosized phases.The in-situ reaction path could be expressed as:Nb_(2)O_(5)+Al®Nb+Al_(2)O_(3),and Nb+B_(4)C®NbB_(2)+NbC.