High-performance SiO_(x)/MgO_(x)electron-selective contacts for crystalline silicon solar cells

High carrier recombination loss at the metal and silicon contact regions is one of the dominant factors constraining the power conversion efficiency(PCE)of crystalline silicon(c-Si)solar cells.Metal compound-based carrier-selective contacts are being intensively developed to address this issue.In this work,we present a high-performance electron-selective SiO_(x)/MgO_(x)contact for c-Si solar cells.The SiO_(x)/MgO_(x)stack is prepared by thermally-grown SiO_(x)(∼0.7 nm)and thermally-evaporated MgO_(x)(~1.0 nm).The electron selectivity of SiO_(x)/MgO_(x)contact is investigated by measuring the surface passivation and the contact resistivity(ρ_(c))on the c-Si surface.The results demonstrate that optimized SiO_(x)/MgO_(x)contact displays a very lowρ_(c)(3.4 mΩcm^(2))and a good surface passivation on an n-type c-Si surface simultaneously.A high PCE of 21.1%is achieved on an n-type c-Si solar cell featuring a full-area SiO_(x)/MgO_(x)rear contact.

Potential risk of colonization of Bulinus globosus in the mainland of China under climate change

Background: Bulinus globosus,the main intermediate snail host of Schistosoma haematobium.The increased contacts between Africa and China could even lead to large-scale dissemination of B.globosus in China.Temperature is the key factor affecting fresh-water snail transmission.This study predicted potential risk of colonization of B.globosus in the mainland of China under climate change.Methods: We investigated minimum and maximum temperatures for B.globosus eggs,juveniles and adult snails kept under laboratory conditions to find the most suitable range by pinpointing the median effective temperatures(ET50).We also assessed the influence of temperature on spawning and estimated the accumulated temperature(AT).The average air temperatures between 1955 and 2019 in January and July,the coldest and hottest months in China,respectively,were collected from national meteorological monitoring stations and investigated in a geographic information system(GIS)using empirical Bayesian Kriging to evaluate the theoretical possibility for distribution of B.globosus in southern China based on temperature.Results: The effective minimum temperature(ET50min)for eggs,juveniles,adult snails and spawning were 8.5,7.0,7.0,14.9℃,respectively,with the corresponding maximum values(ET50max)of 36.6,40.5,40.2 and 38.1℃.The AT was calculated at 712.1±64.9℃·d.In 1955,the potential B.globosus distribution would have had a northern boundary stretching from the coastal areas of Guangdong Province and Guangxi Autonomous Region to southern Yunnan Province.Since then,this line has gradually moved northward.Conclusions: Annual regeneration of B.globosus can be supported by the current climate conditions in the mainland of China,and a gradual expansion trend from south to north is shown in the study from 2015 to 2019.Thus,there is a potential risk of colonization of B.globosus in the mainland of China under climate change.