Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on th...Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.展开更多
Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation,leading to new ways to break efficiency limits for solar energy conve...Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation,leading to new ways to break efficiency limits for solar energy conversion.In this work,we demonstrate the observation and modulation of slow relaxation in uniformly mixed tin-lead perovskites(MASn_(x)Pb_(1-x)I_(3)and CsSn_(x)Pb_(1-x)I_(3)nanocrystals).Transient absorption measurements reveal that slow cooling mediated by a hot phonon bottleneck effect appears at carrier densities above~10^(18)cm^(−3)for tin-lead alloy nanocrystals,and tin addition is found to give rise to suppressed cooling.Within the alloy nanoparticles,the combination of a newly introduced high-energy band,screened Fröhlich interaction,suppressed Klemens decay and reduced thermal conductivity(acoustic phonon transport)with increased tin content contributes to the slowed relaxation.For inorganic nanocrystals where defect states couple strongly with carriers,sodium doping has been confirmed to benefit in maintaining hot carriers by decoupling them from deep defects,leading to a decreased energy-loss rate during thermalization and an enhanced hot phonon bottleneck effect.The slow cooling we observe uncovers the intrinsic photophysics of perovskite nanocrystals,with implications for photovoltaic applications where suppressed cooling could lead to hot-carrier solar cells.展开更多
基金X.L.and T.W.are contributed equally to this work.W.Z.acknowledges the Engineering and Physical Sciences Research Council(EPSRC)New Investigator Award(2018EP/R043272/1)+8 种基金Marie Skłodowska-Curie Actions Individual Fellowships(839136)H.L.acknowledges the Newton Advanced Fellowship(192097)X.L.acknowledges the financial support from Zhengzhou University ScholarshipT.W thanks the University of Surrey Doctoral College for financial supportS.J.S.gratefully acknowledges the support of EPSRC(UK)under grant number EP/N021037/1L.D.thanks the China Scholarship Council and the Cambridge Trusts for fundingR.C.K.and J.A.S.thank the company Xenocs for their ongoing support through the X-ray scattering user program at the University of Sheffield and the EPSRC for funding the purchase of this instrumentZ.W.,Y.S.,and G.S.thank the financial support from Zhengzhou Materials Genome InstituteS.D.S.and K.J.acknowledge the Royal Society for funding。
文摘Recent advances in heterojunction and interfacial engineering of perovskite solar cells(PSCs)have enabled great progress in developing highly efficient and stable devices.Nevertheless,the effect of halide choice on the formation mechanism,crystallography,and photoelectric properties of the lowdimensional phase still requires further detailed study.In this work,we present key insights into the significance of halide choice when designing passivation strategies comprising large organic spacer salts,clarifying the effect of anions on the formation of quasi-2D/3D heterojunctions.To demonstrate the importance of halide influences,we employ novel neo-pentylammonium halide salts with different halide anions(neoPAX,X=I,Br,or Cl).We find that regardless of halide selection,iodide-based(neoPA)_(2)(FA)_((n-1))PbnI_((3n+1))phases are formed above the perovskite substrate,while the added halide anions diffuse and passivate the perovskite bulk.In addition,we also find the halide choice has an influence on the degree of dimensionality(n).Comparing the three halides,we find that chloride-based salts exhibit superior crystallographic,enhanced carrier transport,and extraction compared to the iodide and bromide analogs.As a result,we report high power conversion efficiency in quasi-2D/3D PSCs,which are optimal when using chloride salts,reaching up to 23.35%,and improving long-term stability.
文摘Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation,leading to new ways to break efficiency limits for solar energy conversion.In this work,we demonstrate the observation and modulation of slow relaxation in uniformly mixed tin-lead perovskites(MASn_(x)Pb_(1-x)I_(3)and CsSn_(x)Pb_(1-x)I_(3)nanocrystals).Transient absorption measurements reveal that slow cooling mediated by a hot phonon bottleneck effect appears at carrier densities above~10^(18)cm^(−3)for tin-lead alloy nanocrystals,and tin addition is found to give rise to suppressed cooling.Within the alloy nanoparticles,the combination of a newly introduced high-energy band,screened Fröhlich interaction,suppressed Klemens decay and reduced thermal conductivity(acoustic phonon transport)with increased tin content contributes to the slowed relaxation.For inorganic nanocrystals where defect states couple strongly with carriers,sodium doping has been confirmed to benefit in maintaining hot carriers by decoupling them from deep defects,leading to a decreased energy-loss rate during thermalization and an enhanced hot phonon bottleneck effect.The slow cooling we observe uncovers the intrinsic photophysics of perovskite nanocrystals,with implications for photovoltaic applications where suppressed cooling could lead to hot-carrier solar cells.
