Ethylene-propene copolymers have been synthesized by three C1-symmetric metallocene molecules(1,2,and 3),having tert-butyl substituents on the Cp moiety,on the fluorenyl moiety,or on both moieties,and methylaluminoxan...Ethylene-propene copolymers have been synthesized by three C1-symmetric metallocene molecules(1,2,and 3),having tert-butyl substituents on the Cp moiety,on the fluorenyl moiety,or on both moieties,and methylaluminoxane(MAO)at different polymerization temperatures and monomer concentrations.Copolymers were investigated by 13 C-NMR,1 H-NMR,and SEC analyses.A relationship was found between[EEE]/[E]ratios and copolymer molar masses in each series:the higher the[EEE]/[E]ratio,the lower the copolymer molar mass.At parity of[EEE]/[E]ratio,copolymer molar mass follows the order 1>>3>2.Chain end group analysis reveals that copolymers mainly terminate when propene is the last inserted unit,confirming that it is the greater facility of Mt-P-E-poly(E-co-P)to terminate that influences the copolymer molar mass.Among the catalysts considered,catalyst 1,which gives syndiospecific polypropene,gives greater activities,comonomer incorporation,and molar masses.Catalyst 3,which gives isospecific polypropene,in copolymerization performs better than 2,having the same bridge,with respect to activities,ethylene content,and molar masses.The good performance of this catalyst arises from the not necessity of polymer chain to back skip when ethylene is the last inserted unit.展开更多
Mixed cation strategy greatly benefits the enhancement of device performance and chemical stability.However,adverse impact also accompanies the mixed cation system simultaneously.It brings the compositional instabilit...Mixed cation strategy greatly benefits the enhancement of device performance and chemical stability.However,adverse impact also accompanies the mixed cation system simultaneously.It brings the compositional instability,wherein the homogeneous film is likely to segregate into multi-phases during the fabrication and ageing process,thus resulting in the efficiency reduction of perovskite solar cells(PSCs)devices.This review focuses on the cation induced phase segregation,and elucidates the segregation mechanisms from the perspectives of film formation and ageing process,respectively.Furthermore,the influence of cation segregation on device performance and operational stability are discussed.And based on these understandings,viable strategies are proposed for the design of phase-stable mixed composition halide perovskites and for suppressing segregation to benefit its development towards commercial applications.展开更多
基金financially supported by Total. We thank G. Zannoni and D. Piovani (ISMAC) for their valuable cooperation in NMR and SEC analysis
文摘Ethylene-propene copolymers have been synthesized by three C1-symmetric metallocene molecules(1,2,and 3),having tert-butyl substituents on the Cp moiety,on the fluorenyl moiety,or on both moieties,and methylaluminoxane(MAO)at different polymerization temperatures and monomer concentrations.Copolymers were investigated by 13 C-NMR,1 H-NMR,and SEC analyses.A relationship was found between[EEE]/[E]ratios and copolymer molar masses in each series:the higher the[EEE]/[E]ratio,the lower the copolymer molar mass.At parity of[EEE]/[E]ratio,copolymer molar mass follows the order 1>>3>2.Chain end group analysis reveals that copolymers mainly terminate when propene is the last inserted unit,confirming that it is the greater facility of Mt-P-E-poly(E-co-P)to terminate that influences the copolymer molar mass.Among the catalysts considered,catalyst 1,which gives syndiospecific polypropene,gives greater activities,comonomer incorporation,and molar masses.Catalyst 3,which gives isospecific polypropene,in copolymerization performs better than 2,having the same bridge,with respect to activities,ethylene content,and molar masses.The good performance of this catalyst arises from the not necessity of polymer chain to back skip when ethylene is the last inserted unit.
基金National Natural Science Foundation of China(22109057,21805010,21975028,52172182,22011540377,22005035)Beijing Municipal Science and Technology Project(Z181100005118002)+2 种基金Beijing Municipal Natural Science Foundation(JQ19008)the China Postdoctoral Science Foundation(Grant No.2020TQ0043,2020M680012)Research Foundation of Jiangxi Educational Committee(GJJ200836).
文摘Mixed cation strategy greatly benefits the enhancement of device performance and chemical stability.However,adverse impact also accompanies the mixed cation system simultaneously.It brings the compositional instability,wherein the homogeneous film is likely to segregate into multi-phases during the fabrication and ageing process,thus resulting in the efficiency reduction of perovskite solar cells(PSCs)devices.This review focuses on the cation induced phase segregation,and elucidates the segregation mechanisms from the perspectives of film formation and ageing process,respectively.Furthermore,the influence of cation segregation on device performance and operational stability are discussed.And based on these understandings,viable strategies are proposed for the design of phase-stable mixed composition halide perovskites and for suppressing segregation to benefit its development towards commercial applications.
