Pseudo-bulk heterojunction(BHJ)fabricated by sequential casting of donor and acceptor layers has been recently demonstrated as a superior structure to prepare organic solar cells(OSCs)with enhanced efficiency compared...Pseudo-bulk heterojunction(BHJ)fabricated by sequential casting of donor and acceptor layers has been recently demonstrated as a superior structure to prepare organic solar cells(OSCs)with enhanced efficiency compared to the conventional BHJ OSCs cast from a common solution of donors and acceptors.However,molecular diffusion and aggregation within the pseudo-BHJ layer bring great challenges to fully realize the advantage of pseudo-BHJ structure.Herein,a solution-incubated pre-aggregation strategy is employed to tune the nanoscale aggregates of non-fullerene acceptor(NFA)BTP-e C11 and N3 to substantially enhance device power-conversion efficiency(PCE).NFA pre-aggregates are incubated in solutions via aging or adding antisolvent,and then sequentially cast onto D18 fibrillar network,which then penetrate to form a pseudo-BHJ structure with appropriate domain sizes to ensure superior charge mobilities.While the conventional pseudo-BHJ OSCs obtain inferior PCEs below 17%compared with normal BHJ OSCs,NFA pre-aggregates help to achieve remarkable PCEs of 17.7%and 17.5%for D18/BTP-e C11 and D18/N3 pseudo-BHJ OSCs.This work demonstrates that the solution-incubated nanoscale pre-aggregation is an efficient approach to regulate molecular diffusion and aggregation to guarantee high performance pseudo-BHJ OSCs.展开更多
Carbon nanodots （CDs） formed by hydrothermal dehydration occur as mixtures of differently sized nanoparticles with different degrees of carbonization. Common ultracentrifugation has failed in sorting them, owing to ...Carbon nanodots （CDs） formed by hydrothermal dehydration occur as mixtures of differently sized nanoparticles with different degrees of carbonization. Common ultracentrifugation has failed in sorting them, owing to their extremely high colloidal stability. Here, we introduce an ultracentrifugation method using a hydrophilicity gradient to sort such non-sedimental CDs. CDs, synthesized from citric acid and ethylenediamine, were pre-treated by acetone to form clusters. Such clusters ＂de-clustered＂ as media comprising gradients of ethanol they were forced to sediment through and water with varied volume ratios. Primary CDs with varied sizes and degrees of carbonization detached from the clusters to become well dispersed in the corresponding gradient layers. Their settling level was highly dependent on the varied hydrophilicity and solubility of the environmental media. Thus, the proposed hydrophilicity-triggered sorting strategy could be used for other nanoparticles with extremely high colloidal stability, which further widens the range of sortable nanoparticles. Furthermore, according to careful analysis of the changes in size, composition, quantum yield, and transient fluorescence of typical CDs in the post-separation fractions, it was concluded that the photoluminescence of the as-prepared hydrothermal carbonized CDs mainly arose from the particles＇ surface molecular state rather than their sizes.展开更多
基金supported by the National Natural Science Foundation of China(52073221,21774097)the Fundamental Research Funds for the Central Universities(WUT:2021III016JC,2020YB-004)of China。
文摘Pseudo-bulk heterojunction(BHJ)fabricated by sequential casting of donor and acceptor layers has been recently demonstrated as a superior structure to prepare organic solar cells(OSCs)with enhanced efficiency compared to the conventional BHJ OSCs cast from a common solution of donors and acceptors.However,molecular diffusion and aggregation within the pseudo-BHJ layer bring great challenges to fully realize the advantage of pseudo-BHJ structure.Herein,a solution-incubated pre-aggregation strategy is employed to tune the nanoscale aggregates of non-fullerene acceptor(NFA)BTP-e C11 and N3 to substantially enhance device power-conversion efficiency(PCE).NFA pre-aggregates are incubated in solutions via aging or adding antisolvent,and then sequentially cast onto D18 fibrillar network,which then penetrate to form a pseudo-BHJ structure with appropriate domain sizes to ensure superior charge mobilities.While the conventional pseudo-BHJ OSCs obtain inferior PCEs below 17%compared with normal BHJ OSCs,NFA pre-aggregates help to achieve remarkable PCEs of 17.7%and 17.5%for D18/BTP-e C11 and D18/N3 pseudo-BHJ OSCs.This work demonstrates that the solution-incubated nanoscale pre-aggregation is an efficient approach to regulate molecular diffusion and aggregation to guarantee high performance pseudo-BHJ OSCs.
文摘Carbon nanodots （CDs） formed by hydrothermal dehydration occur as mixtures of differently sized nanoparticles with different degrees of carbonization. Common ultracentrifugation has failed in sorting them, owing to their extremely high colloidal stability. Here, we introduce an ultracentrifugation method using a hydrophilicity gradient to sort such non-sedimental CDs. CDs, synthesized from citric acid and ethylenediamine, were pre-treated by acetone to form clusters. Such clusters ＂de-clustered＂ as media comprising gradients of ethanol they were forced to sediment through and water with varied volume ratios. Primary CDs with varied sizes and degrees of carbonization detached from the clusters to become well dispersed in the corresponding gradient layers. Their settling level was highly dependent on the varied hydrophilicity and solubility of the environmental media. Thus, the proposed hydrophilicity-triggered sorting strategy could be used for other nanoparticles with extremely high colloidal stability, which further widens the range of sortable nanoparticles. Furthermore, according to careful analysis of the changes in size, composition, quantum yield, and transient fluorescence of typical CDs in the post-separation fractions, it was concluded that the photoluminescence of the as-prepared hydrothermal carbonized CDs mainly arose from the particles＇ surface molecular state rather than their sizes.
