CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly co...CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.展开更多
The rational design of polymer acceptors with strong and broad absorption is critical to improve photovoltaic performance.In this work,a new polymer acceptor PY9-T based on heptacyclic benzotriazole(Y9-C16)as a buildi...The rational design of polymer acceptors with strong and broad absorption is critical to improve photovoltaic performance.In this work,a new polymer acceptor PY9-T based on heptacyclic benzotriazole(Y9-C16)as a building block and thiophene unit as the linking unit was synthesized,which exhibited a low bandgap(1.37 eV)and a high extinction coefficient of the neat film(1.44×10^(5) cm^(−1)).When PY9-T was blended with the wide bandgap polymer donor PBDB-T,the all-polymer solar cells(APSCs)showed a high power conversion efficiency(PCE)of 10.45%with both high open circuit voltage of 0.881 V and short-circuit current density of 19.82 mA/cm^(2).In addition,APSCs based on PY9-T show good thermal stability,as evidenced by slight changes morphologies when annealed at 100℃.These results suggest that Y9-C16 provides a new building block to develop efficient and stable polymer acceptors.展开更多
Windbelt generators have been proposed as small, green power sources for battery charging applications. Some of the reported results lack detailed information about how key parameters influence the output power of the...Windbelt generators have been proposed as small, green power sources for battery charging applications. Some of the reported results lack detailed information about how key parameters influence the output power of the generator. In this work, we built prototypes with different architectures to study the voltage generation and power delivery as functions of belt tension, length, and electrical load at various wind speeds. We also studied the maximum power delivery conditions before the breakdown of the belt oscillation occurs. Our results are obtained from windbelt generators with two types of architectures： a conventional design with an adjustable belt that uses weight for tension control, and a revised design with a belt oscillation perpendicular to the coil axis. We have concluded that the breakdown of the belt oscillation at lower output resistances is a primary bottleneck that will limit windbelt systems to only very low power applications.展开更多
Three two-dimensional like conjugated copolymers PFSDCN,PFSDTA and PFSDCNIO,which consist of alternating fluorene and triphenylamine main chain,and different pendant acceptor groups (malononitrile,1,3-diethtyl-2-thiob...Three two-dimensional like conjugated copolymers PFSDCN,PFSDTA and PFSDCNIO,which consist of alternating fluorene and triphenylamine main chain,and different pendant acceptor groups (malononitrile,1,3-diethtyl-2-thiobarbituric acid and 2-(1,2-dihydro-1-oxoinden-3-ylidene)malononitrile) with thiophene as π-bridge,have been designed,synthesized and characterized.The structure-property relationships of the two-dimensional like conjugated copolymers were systematically investigated.The absorption spectra,band gaps,and energy levels of the polymers were effectively tuned by simply attaching different acceptor groups.As the electron-withdrawing ability of the acceptors increased,the band gaps of the polymers were narrowed from 2.05 to 1.61 eV;meanwhile,the LUMO energy levels of the polymers decreased from -3.27 to -3.75 eV,whereas their relatively deep HOMO energy levels of ～-5.35 eV were preserved.BHJ solar cells were fabricated and characterized by using the three polymers as donor materials and the highest power conversion efficiency of 2.87% was achieved for the device based on PFSDTA:(6,6)-phenyl-C71-butyric acid methyl ester blend.展开更多
Normally, it is difficult to directly measure the bandgaps of perovskite based on methylammonium(MA) or formamidinium(FA) at high temperatures due to material decomposition. We prevent the decomposition by keeping the...Normally, it is difficult to directly measure the bandgaps of perovskite based on methylammonium(MA) or formamidinium(FA) at high temperatures due to material decomposition. We prevent the decomposition by keeping the synthesized perovskite films(MAPbI_3 and MAPbI_3) in organic iodide vapors, then measure the in-situ resistance of the films at varied temperatures, and further evaluate the bandgaps of these two materials. The evaluated bandgaps are consistent with the results from ultraviolet-visible(UV-vis) absorption spectrum. The bandgap of MAPbI_3 decreases with temperature above 95 ℃, whereas that of FAPbI_3 first increases with temperature from 95 ℃ to 107 ℃ and then decreases with temperature above 107 ℃.展开更多
Narrow-bandgap tin-lead(Sn-Pb)mixed perovskite solar cells(PSCs)play a key role in constructing perovskite tandem solar cells that are potential to overpass Shockley-Queisser limit.A robust,chemically stable and lowte...Narrow-bandgap tin-lead(Sn-Pb)mixed perovskite solar cells(PSCs)play a key role in constructing perovskite tandem solar cells that are potential to overpass Shockley-Queisser limit.A robust,chemically stable and lowtemperature-processed hole transporting layer(HTL)is essential for building high-efficiency Sn-Pb solar cells and perovskite tandem solar cells.Here,we explore a roomtemperature-processed NiOx(L-NiOx)HTL based on nanocrystals(NCs)for Sn-Pb PSCs.In comparison with hightemperature-annealed NiOx(H-NiOx)film,the L-NiOx film shows deeper valence band and lower trap density,which increases the built-in potential and reduces carrier recombination,leading to a power conversion efficiency of 18.77%,the record for NiOx-based narrow-bandgap PSCs.Furthermore,the device maintains about 96%of its original efficiency after 50 days.This work provides a robust and room-temperatureprocessed HTL for highly efficient and stable narrow-bandgap PSCs.展开更多
We have combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%. By covering tra...We have combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%. By covering transparent graphene or carbon nanotube （CNT） films on selected positions along macroscopically long CdSe nanobelts, we have demonstrated the fabrication of active solar cells with many different configurations and parallel connections from individual or multiple assembled nanobelts. The graphene-CdSe nanobelt solar cells reported here show a great flexibility in creating diverse device architectures, and might be scaled up for cell integration based on assembled nanobelt arrays and patterned graphene （or CNT） films.展开更多
[020]-oriented tin sulfide nanobelts with a length/thickness ratio of 100 have been synthesized by a facile hydrothermal method without any surfactants, and the nanobelts have shown good strain-accommodating propertie...[020]-oriented tin sulfide nanobelts with a length/thickness ratio of 100 have been synthesized by a facile hydrothermal method without any surfactants, and the nanobelts have shown good strain-accommodating properties as well as good electrochemical performance as the anode for Li-ion batteries. The formation of the nanobelts results from a precipitation-dissolution-transformation mechanism, and the [020] oriented growth can be ascribed to the {010} facet family having the lowest atomic density. In particular, SnS shows clear Li-Sn alloying/de-alloying reversible reactions in the potential range 0.1-1.0 V. Based on galvanostatic measurements and electrochemical impedance spectroscopy, SnS nanobelts have shown impressive rate performance. The post-cycled SnS nanobelts were completely transformed into metallic tin, and preserved the one-dimensional structure due to their flexibility which accommodates the large volumetric expansion.展开更多
Three low bandgap non-fullerene acceptors based on thieno[3,2-b]thiophene fused core with different ending groups, named TTIC-M, TTIC, TTIC-F were designed and synthesized. Using a wide bandgap polymer PBDB-T as donor...Three low bandgap non-fullerene acceptors based on thieno[3,2-b]thiophene fused core with different ending groups, named TTIC-M, TTIC, TTIC-F were designed and synthesized. Using a wide bandgap polymer PBDB-T as donor to form a complementary absorption in the range of 300–900 nm, high efficencies of 9.97%, 10.87% and 9.51% were achieved for TTIC-M, TTIC and TTFC-F based photovoltaic devices with impressively high short circuit current over21 mA cm^-2.展开更多
A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2...A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2, The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.展开更多
文摘CdS thin films were prepared by chemical-bath-deposited method and the effect of temperature and time on the properties of CdS thin films was studied. Independent of the deposited temperature, the growth was mainly controlled by the ion-by-ion growth mechanism at the beginning of the film deposition, then the cluster-by-cluster mechanism came to be dominant. The growth rate increased faster with the increasing of temperature until the thickness reached the limitation, then thickness instead become thinner. The scanning electron micro- scope results revealed that the morphology of the CdS film changed from pinholes to rough, inhomogeneous surface with increasing deposition time and deposition temperature. The X- ray diffraction results showed the film structure was a mixture of two phases： hexagonal and cubic, and it was very important to controll deposition time to the film＇s crystal phase. All films in depth of approxilnate 100 nm existed above 65% transmittance, the absorption edge became ＂red-shift＂ with temperature rising. At 60 and 70℃, with 20 min deposited-time, the energy band gap was more than 2.42 eV and decreased with time, while at 80 and 90℃ the energy band gap was less than 2.42 eV and increased little when the time changed from 10min to 15 nfin at 80℃.
基金Project(21875286)supported by the National Natural Science Foundation of China。
文摘The rational design of polymer acceptors with strong and broad absorption is critical to improve photovoltaic performance.In this work,a new polymer acceptor PY9-T based on heptacyclic benzotriazole(Y9-C16)as a building block and thiophene unit as the linking unit was synthesized,which exhibited a low bandgap(1.37 eV)and a high extinction coefficient of the neat film(1.44×10^(5) cm^(−1)).When PY9-T was blended with the wide bandgap polymer donor PBDB-T,the all-polymer solar cells(APSCs)showed a high power conversion efficiency(PCE)of 10.45%with both high open circuit voltage of 0.881 V and short-circuit current density of 19.82 mA/cm^(2).In addition,APSCs based on PY9-T show good thermal stability,as evidenced by slight changes morphologies when annealed at 100℃.These results suggest that Y9-C16 provides a new building block to develop efficient and stable polymer acceptors.
文摘Windbelt generators have been proposed as small, green power sources for battery charging applications. Some of the reported results lack detailed information about how key parameters influence the output power of the generator. In this work, we built prototypes with different architectures to study the voltage generation and power delivery as functions of belt tension, length, and electrical load at various wind speeds. We also studied the maximum power delivery conditions before the breakdown of the belt oscillation occurs. Our results are obtained from windbelt generators with two types of architectures： a conventional design with an adjustable belt that uses weight for tension control, and a revised design with a belt oscillation perpendicular to the coil axis. We have concluded that the breakdown of the belt oscillation at lower output resistances is a primary bottleneck that will limit windbelt systems to only very low power applications.
基金supported by the National Natural Science Foundation of China (50990065,51010003,51073058 and 20904011)the National Basic Research Program of China (973 Program) (2009CB623601)+1 种基金the Fundamental Research Funds for the Central Universities,South China University of Technology (2009220012,2009220043)the supported UGC grant (#400897) of the University of Hong Kong and Hong Kong Research Grants Council (HKU#712108 and HKU#712010) from the Research Grants Council of the Hong Kong Special Administrative Region,China
文摘Three two-dimensional like conjugated copolymers PFSDCN,PFSDTA and PFSDCNIO,which consist of alternating fluorene and triphenylamine main chain,and different pendant acceptor groups (malononitrile,1,3-diethtyl-2-thiobarbituric acid and 2-(1,2-dihydro-1-oxoinden-3-ylidene)malononitrile) with thiophene as π-bridge,have been designed,synthesized and characterized.The structure-property relationships of the two-dimensional like conjugated copolymers were systematically investigated.The absorption spectra,band gaps,and energy levels of the polymers were effectively tuned by simply attaching different acceptor groups.As the electron-withdrawing ability of the acceptors increased,the band gaps of the polymers were narrowed from 2.05 to 1.61 eV;meanwhile,the LUMO energy levels of the polymers decreased from -3.27 to -3.75 eV,whereas their relatively deep HOMO energy levels of ～-5.35 eV were preserved.BHJ solar cells were fabricated and characterized by using the three polymers as donor materials and the highest power conversion efficiency of 2.87% was achieved for the device based on PFSDTA:(6,6)-phenyl-C71-butyric acid methyl ester blend.
基金supported by the National Natural Science Foundation of China(No.61504097)the Natural Science Foundation of Tianjin(No.14JCYBJC42800)+1 种基金the Scientific Developing Foundation of Tianjin Education Commission(No.20140423)the National Key Scientific Instrument and Equipment Development Project(No.2014YQ120351)
文摘Normally, it is difficult to directly measure the bandgaps of perovskite based on methylammonium(MA) or formamidinium(FA) at high temperatures due to material decomposition. We prevent the decomposition by keeping the synthesized perovskite films(MAPbI_3 and MAPbI_3) in organic iodide vapors, then measure the in-situ resistance of the films at varied temperatures, and further evaluate the bandgaps of these two materials. The evaluated bandgaps are consistent with the results from ultraviolet-visible(UV-vis) absorption spectrum. The bandgap of MAPbI_3 decreases with temperature above 95 ℃, whereas that of FAPbI_3 first increases with temperature from 95 ℃ to 107 ℃ and then decreases with temperature above 107 ℃.
基金the National Key Research and Development Program of China(2016YFA0204000)the National Natural Science Foundation of China(61935016,U1632118 and 21571129)+3 种基金start-up funding from ShanghaiTech Universitythe Center for High-resolution Electron Microscopy(C?EM)at ShanghaiTech University(EM02161943)Young 1000 Talents ProgramScience Fund for Creative Research Groups(21421004)。
文摘Narrow-bandgap tin-lead(Sn-Pb)mixed perovskite solar cells(PSCs)play a key role in constructing perovskite tandem solar cells that are potential to overpass Shockley-Queisser limit.A robust,chemically stable and lowtemperature-processed hole transporting layer(HTL)is essential for building high-efficiency Sn-Pb solar cells and perovskite tandem solar cells.Here,we explore a roomtemperature-processed NiOx(L-NiOx)HTL based on nanocrystals(NCs)for Sn-Pb PSCs.In comparison with hightemperature-annealed NiOx(H-NiOx)film,the L-NiOx film shows deeper valence band and lower trap density,which increases the built-in potential and reduces carrier recombination,leading to a power conversion efficiency of 18.77%,the record for NiOx-based narrow-bandgap PSCs.Furthermore,the device maintains about 96%of its original efficiency after 50 days.This work provides a robust and room-temperatureprocessed HTL for highly efficient and stable narrow-bandgap PSCs.
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.
文摘We have combined two planar nanostructures, graphene and CdSe nanobelts, to construct Schottky junction solar cells with open-circuit voltages of about 0.5 V and cell efficiencies on the order of 0.1%. By covering transparent graphene or carbon nanotube （CNT） films on selected positions along macroscopically long CdSe nanobelts, we have demonstrated the fabrication of active solar cells with many different configurations and parallel connections from individual or multiple assembled nanobelts. The graphene-CdSe nanobelt solar cells reported here show a great flexibility in creating diverse device architectures, and might be scaled up for cell integration based on assembled nanobelt arrays and patterned graphene （or CNT） films.
基金Acknowledgements This work was supported by the State Key Project of Fundamental Research for Nanoscience and Nano- technology （Nos. 2011CB932401 and 2011CBA00500）, and the National Natural Science Foundation of China （Nos. 20921001 and 21051001）. We are grateful to Associate Professor Jiaping Wang and lab assistant Fei Zhao in the Tsinghua-Foxconn Nanocenter for their generous help in the fabrication of batteries.
文摘[020]-oriented tin sulfide nanobelts with a length/thickness ratio of 100 have been synthesized by a facile hydrothermal method without any surfactants, and the nanobelts have shown good strain-accommodating properties as well as good electrochemical performance as the anode for Li-ion batteries. The formation of the nanobelts results from a precipitation-dissolution-transformation mechanism, and the [020] oriented growth can be ascribed to the {010} facet family having the lowest atomic density. In particular, SnS shows clear Li-Sn alloying/de-alloying reversible reactions in the potential range 0.1-1.0 V. Based on galvanostatic measurements and electrochemical impedance spectroscopy, SnS nanobelts have shown impressive rate performance. The post-cycled SnS nanobelts were completely transformed into metallic tin, and preserved the one-dimensional structure due to their flexibility which accommodates the large volumetric expansion.
基金supported by the Minstry of Science and Technology(2014CB643502)the National Natural ScienceFoundation of China(91633301,51422304 and 91433101)+1 种基金PCSIRT(IRT1257)Tianjin city(17JCZDJC31100)
文摘Three low bandgap non-fullerene acceptors based on thieno[3,2-b]thiophene fused core with different ending groups, named TTIC-M, TTIC, TTIC-F were designed and synthesized. Using a wide bandgap polymer PBDB-T as donor to form a complementary absorption in the range of 300–900 nm, high efficencies of 9.97%, 10.87% and 9.51% were achieved for TTIC-M, TTIC and TTFC-F based photovoltaic devices with impressively high short circuit current over21 mA cm^-2.
文摘A nanocomposite material of SnO2-reduced graphene oxide nanoribbons has been developed. In this composite, the reduced graphene oxide nanoribbons are uniformly coated by nanosized SnO2 that formed a thin layer of SnO2 on the surface. When used as anodes in lithium ion batteries, the composite shows outstanding electrochemical performance with the high reversible discharge capacity of 1,027 mAh/g at 0.1 A/g after 165 cycles and 640 mAh/g at 3.0 A/g after 160 cycles with current rates varying from 0.1 to 3.0 A/g and no capacity decay after 600 cycles compared to the second cycle at a current density of 1.0 A/g. The high reversible capacity, good rate performance and excellent cycling stability of the composite are due to the synergistic combination of electrically conductive reduced graphene oxide nanoribbons and SnO2, The method developed here is practical for the large-scale development of anode materials for lithium ion batteries.
