High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coat...High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH_3NH_3PbI_3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.展开更多
The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target.The precursors are selenized in the H_(2)Se-containing atmosphere to prepare(Ag,Cu)(In,Ga)Se...The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target.The precursors are selenized in the H_(2)Se-containing atmosphere to prepare(Ag,Cu)(In,Ga)Se_(2)(ACIGS)absorbers.The beneficial effects of Ag doping are demonstrated and their mechanism is explained.It is found that Ag doping significantly improves the films crystallinity.This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping.This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity.The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing.It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films.Therefore,carrier recombination is reduced and carrier transport is improved.The negative effects of excessive Ag are also demonstrated and their origin is revealed.Because the atomic size of Ag is different from that of Cu,for the Ag/(Ag+Cu)ratio(AAC)≥0.030,lattice distortion is aggravated,and significant micro-strain appears.The atomic radius of Ag is close to those of In and Ga,so that the continued increase in AAC will give rise to the Ag;or Ag;defects.Both the structural and compositional defects degrade the quality of the absorbers and the device performance.An excellent absorber can be obtained at AAC of 0.015.展开更多
Enhancing the mechanical strength of highly conductive pure metals usually causes significant reduction in their electrical conductivity.For example,introducing phase/matrix interfaces or more grain boundaries,are com...Enhancing the mechanical strength of highly conductive pure metals usually causes significant reduction in their electrical conductivity.For example,introducing phase/matrix interfaces or more grain boundaries,are common and effective methods to strengthen metals.But it simultaneously increases the electron scattering at the interface,thus reducing the electrical conductivity.In this study,we demonstrate that pure aluminum(Al)/carbon nanotubes(CNTs)nanocomposites prepared by friction stir processing have successfully broken through these limitations.The yield strength and tensile strength of Al/CNTs nanocomposites have improved by 104.7%and 51.8%compared to pure Al,while the electrical conductivity remained comparable to that of pure Al.To explore the potential mechanisms,the interface between CNTs and Al was examined and characterized by transmission electron microscopy(TEM)and Raman spectroscopy.Little interfacial reaction compounds were present and no visible physical gaps were observed at CNTs and Al interfaces.We defined it as a clean and tightly bonded interface.Although the quantity of phase interface has increased,the electrical conductivity of the nanocomposite remains approximately unchanged.We attribute the preserved electrical conductivity to the clean and tightly bonded CNTs/Al interface in the nanocomposite.展开更多
Carbon nanotube-silicon(CNT-Si)solar cells represent one of the alternative photovoltaic techniques with potential for low cost and high efficiency.Here,we report a method to improve solar cell performance by depositi...Carbon nanotube-silicon(CNT-Si)solar cells represent one of the alternative photovoltaic techniques with potential for low cost and high efficiency.Here,we report a method to improve solar cell performance by depositing conventional transitional metal oxides such as WO_(3)and establishing a collaborative system,in which CNTs are well-embedded within the WO_(3)layer and both of them are in close contact to Si substrate.This unique collaborative system optimizes the overall energy conversion process including the light absorption(antireflection by WO_(3)),carrier separation(forming quasi p-n junction)and charge collection(CNT conductive network throughout the oxide layer).Combining with our previous TiO_(2)-coating and HNO_(3)-doping techniques,a solar cell efficiency of>18%at an active area of 0.09 cm 2(air mass 1.5,100 mW/cm^(2))was achieved.The oxide-enhanced CNT-Si solar cells which integrate the advantages of traditional semiconductors and novel nanostructures represent a promising route toward next-generation high-performance silicon-based photovoltaics.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.21463002)Startup Funding of Distinguished Professorship of "1000 Talents Program"(31370086963030)+4 种基金Shenzhen Jiawei Photovoltaic Lighting Co.,Ltd.Tsinghua University Initiative Scientific Research Program(20161080165)Natural Science Foundation of Xinjiang Uygur Autonomous Region(No.2016D01C008)Opening Project of State Key laboratory of Crystal Material(No.KF1610)Scientific Research Program of the Higher Education Institution of Xinjiang(XJEDU2017M038)
文摘High quality perovskite films with large columnar grains are greatly desired for efficient perovskite solar cells. Here, low volatility N-methyl-2-pyrrolidone(NMP) was added in MAI/IPA solution in a two-step spin-coating method, which promoted the conversion of lead iodide to perovskite. The perovskite films were annealed by a closed-steam annealing method to prolong the recrystallization process of perovskite films assisted by the residual NMP. It leaded to high quality CH_3NH_3PbI_3 perovskite films with large columnar grains due to its enhancement of the Oswald ripening. The large grain perovskite film leaded to efficient carrier transformation and injection, and low recombination. The photovoltaic performance of the perovskite solar cells was improved significantly.
基金supported by the analysis support of the State Key Laboratory of New Ceramics and Fine Processing。
文摘The AgCuInGa alloy precursors with different Ag concentrations are fabricated by sputtering an Ag target and a CuInGa target.The precursors are selenized in the H_(2)Se-containing atmosphere to prepare(Ag,Cu)(In,Ga)Se_(2)(ACIGS)absorbers.The beneficial effects of Ag doping are demonstrated and their mechanism is explained.It is found that Ag doping significantly improves the films crystallinity.This is believed to be due to the lower melting point of chalcopyrite phase obtained by the Ag doping.This leads to a higher migration ability of the atoms that in turn promotes grain boundary migration and improves the film crystallinity.The Ga enrichment at the interface between the absorber and the back electrode is also alleviated during the selenization annealing.It is found that Ag doping within a specific range can passivate the band tail and improve the quality of the films.Therefore,carrier recombination is reduced and carrier transport is improved.The negative effects of excessive Ag are also demonstrated and their origin is revealed.Because the atomic size of Ag is different from that of Cu,for the Ag/(Ag+Cu)ratio(AAC)≥0.030,lattice distortion is aggravated,and significant micro-strain appears.The atomic radius of Ag is close to those of In and Ga,so that the continued increase in AAC will give rise to the Ag;or Ag;defects.Both the structural and compositional defects degrade the quality of the absorbers and the device performance.An excellent absorber can be obtained at AAC of 0.015.
基金This work is supported by Beijing Natural Science Foundation （No. 2122027）, the National Basic Research Program of China （No. 2011CB013000）, the National Natural Science Foundation of China （No. 51372133）, and the Tsinghua University Initiative Scientific Research Program （No. 2012Z02102）.
基金This work was supported by the National Natural Science Foundation of China （NSFC, No. 91127004） and the Beijing City Science and Technology Program （No. Z121100001312005）.
基金This work was supported by the National Natural Science Foundation of China （No. 51172122）, the Foundation for the Author of National Excellent Doctoral Dissertation （No. 2007B37） and the Program for New Century Excellent Talents in University, the Tsinghua University Initiative Scientific Research Pro-gram （No. 20111080939）, and the China Postdoctoral Science Foundation （No. 2011M500310）. We thank Prof. Yonggang Zhao and Dr. Xingli Jiang for their help in testing the capacitors.
文摘Enhancing the mechanical strength of highly conductive pure metals usually causes significant reduction in their electrical conductivity.For example,introducing phase/matrix interfaces or more grain boundaries,are common and effective methods to strengthen metals.But it simultaneously increases the electron scattering at the interface,thus reducing the electrical conductivity.In this study,we demonstrate that pure aluminum(Al)/carbon nanotubes(CNTs)nanocomposites prepared by friction stir processing have successfully broken through these limitations.The yield strength and tensile strength of Al/CNTs nanocomposites have improved by 104.7%and 51.8%compared to pure Al,while the electrical conductivity remained comparable to that of pure Al.To explore the potential mechanisms,the interface between CNTs and Al was examined and characterized by transmission electron microscopy(TEM)and Raman spectroscopy.Little interfacial reaction compounds were present and no visible physical gaps were observed at CNTs and Al interfaces.We defined it as a clean and tightly bonded interface.Although the quantity of phase interface has increased,the electrical conductivity of the nanocomposite remains approximately unchanged.We attribute the preserved electrical conductivity to the clean and tightly bonded CNTs/Al interface in the nanocomposite.
基金Acknowledgements This work was supported by National Science Foundation of China （Nos. 51372133 and 91323304）, Beijing Science and Technology Program （No. D141100000514001）, and Beijing Natural Science Foundation （No. 2122027）.
基金This work was supported by the National Science Foundation of China （NSFC） under grant number 51072005. H. W. Zhu acknowledges the support by theNational Science Foundation of China （No. 50972067）, Tsinghua National Laboratory for Information Science and Technology （TNList） Cross-discipline Foundation and Foundation for the Authors of National Excellent Doctoral Dissertations （No. 201038）. We acknowledge Yan Li from College of Chemistry in Peking University for help in Raman measurement.
基金This work is supported by the National Natural Science Foundation of China （No. 51372133）, the Beijing Science and Technology Program （No. D141100000514001）, the National Program on Key Basic Research Projects （Nos. 2013CB934201, 2011CB013000）, and the Tsinghua University Initiative Scientific Research Program （No. 2012Z02102）.
基金This work is supported by the National Natural Science Foundation of China （NSFC, Grant No.50972067） and the 863 Program （No. 2009AA05Z423）. A. Cao acknowledges the support by the National Science Foundation of China （NSFC, No. 51072005） and C. Huang acknowledges NSFC No. 90922004 for financial support.
基金the Natural Science Foundation of Beijing(No.2212028)the Natural Science Foundation of Henan province(No.202300410371)+1 种基金the National Natural Science Foundation of China(Nos.51325202 and 51872267)the National Key Research and Development Program(No.2020YFA0210702).
文摘Carbon nanotube-silicon(CNT-Si)solar cells represent one of the alternative photovoltaic techniques with potential for low cost and high efficiency.Here,we report a method to improve solar cell performance by depositing conventional transitional metal oxides such as WO_(3)and establishing a collaborative system,in which CNTs are well-embedded within the WO_(3)layer and both of them are in close contact to Si substrate.This unique collaborative system optimizes the overall energy conversion process including the light absorption(antireflection by WO_(3)),carrier separation(forming quasi p-n junction)and charge collection(CNT conductive network throughout the oxide layer).Combining with our previous TiO_(2)-coating and HNO_(3)-doping techniques,a solar cell efficiency of>18%at an active area of 0.09 cm 2(air mass 1.5,100 mW/cm^(2))was achieved.The oxide-enhanced CNT-Si solar cells which integrate the advantages of traditional semiconductors and novel nanostructures represent a promising route toward next-generation high-performance silicon-based photovoltaics.
