It is very important to understand why a small amount of alkali metal doping in Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells can improve the conversion efficiency.In this work,Na-doped CZTSSe is prepared by a simple soluti...It is very important to understand why a small amount of alkali metal doping in Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells can improve the conversion efficiency.In this work,Na-doped CZTSSe is prepared by a simple solution method,and then the effects on the surface properties of the absorber layer,the buffer layer growth,and the modifications of the solar cell performance induced by the Na doping are studied.The surface of the absorber layer is more Cu-depletion and less roughness due to the Na doping.In addition,the contact angle of the surface increases because of Na doping.As a consequence,the thickness of the CdS buffer layer is significantly reduced and the optical losses in the CdS buffer layer are decreased.The difference of quasi-Fermi levels(EFn-EFp) increases with a small amount of Na doping in the CZTSSe solar cell,so that open circuit voltage(VOC) increased significantly.This work offers new insights into the effects of Na doping on CZTSSe via a solution-based approach and provides a deeper understanding of the origin of the efficiency improvement of Na-doped CZTSSe thin film solar cells.展开更多
The application of TiO2-based devices is mainly dependent on their crystalline structure, morphology, size, and exposed facets. Two kinds of TiO2 with different structures, namely TiO2 pompons and TiO2 nanotubes, have...The application of TiO2-based devices is mainly dependent on their crystalline structure, morphology, size, and exposed facets. Two kinds of TiO2 with different structures, namely TiO2 pompons and TiO2 nanotubes, have been prepared by the hydrothermal method. TiO2 with different structures is characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and Brunauer Emmett-Teller （BET） surface area analysis. Solar cells based on poly（3-hexylthiophene） （P3HT） and TiO2 with different structures are fabricated. In the device ITO/TiO2/P3HT/Au, the P3HT is designed to act as the electron donor, and TiO2 pompons and TiO2 nanotubes act as the electron acceptor. The effects of the TiO2 structure on the performance of hybrid heterojunction solar cells are investigated. The device with TiO2 pompons has an open circuit voltage （Voc） of 0.51 V, a short circuit current （Jsc） of 0.21 mA/cm2, and a fill factor （FF） of 28.3%. Another device with TiO2 nanotubes has a Voc of 0.5 V, Jsc of 0.27 mA/cm2, and FF of 28.4%. The results indicate that the TiO2 nanotubes with a unidimensional structure have better carrier transport and light absorption properties than TiO2 pompons. Consequently, the solar cell based on TiO2 nanotubes has a better performance.展开更多
The morphology and interface of perovskite film are very important for the performance of perovskite solar cells(PSCs).The quality of perovskite film,fabricated via two-step spin-coating process,is significantly influ...The morphology and interface of perovskite film are very important for the performance of perovskite solar cells(PSCs).The quality of perovskite film,fabricated via two-step spin-coating process,is significantly influenced by the morphology and crystallinity of PbI2 film.With the addition of additive dimethyl sulfoxide(DMSO)into the PbI2 precursor,the roughness and trap-state density of perovskite film have been significantly reduced,leading to the excellent contact between perovskite layer and subsequent deposited carrier transport layer.Accordingly,the planar heterojunction PSCs with an architecture of ITO/SnO2/perovskite/PTAA/Ag show an efficiency up to 19.02%.Furthermore,PSCs exhibit promising stability in air with a humidity of ~45%,and retain 80% of initial efficiency after being exposed to air for 400 h without any encapsulation.展开更多
The Cu2ZnSnS4 thin film was prepared by a facile solution method without vacuum environment and toxic substance. The formation mechanism of the film was studied by transmission electron microscopy (TEM), X-ray diffrac...The Cu2ZnSnS4 thin film was prepared by a facile solution method without vacuum environment and toxic substance. The formation mechanism of the film was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman scattering measurements. Through cyclic voltammetry and photo-electricity tests, the electrocatalytic activity of the prepared film as the counter electrode of dye-sensitizedsolar cell was also studied. The results show that the mixed precursor solution mainly consists of Cu2SnS3 nanoparticles and Zn ions.After 550 °C annealing process on the precursor film prepared from the mixed solution, Cu2ZnSnS4 thin film is obtained. Besides, itis found that the prepared Cu2ZnSnS4 thin film has the electrocatalytic activity toward the redox reaction of I3?/I? and the dye-sensitized solar cell with the prepared Cu2ZnSnS4 thin film as the counter electrode achieves the efficiency of 1.09%.展开更多
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
基于无机CsPbI_(2)Br的碳基无空穴传输层钙钛矿太阳能电池(carbon based hole transport material freeperovskite solar cells,C-PSCs)具有成本低、易制备和稳定性好等优点而受到广泛关注。研究了空气环境下制备高效稳定的平面异质结Cs...基于无机CsPbI_(2)Br的碳基无空穴传输层钙钛矿太阳能电池(carbon based hole transport material freeperovskite solar cells,C-PSCs)具有成本低、易制备和稳定性好等优点而受到广泛关注。研究了空气环境下制备高效稳定的平面异质结CsPbI_(2)Br C-PSCs的2种制备工艺。首先,通过对反溶剂材料的种类及用量、钙钛矿前驱体溶液浓度等参数的优化,在反溶剂为800μL、钙钛矿前驱体溶液浓度为1.2 mol/L的条件下,采用一步溶液法成功制备了光电转换效率为9.87%的CsPbI_(2)Br C-PSCs。其次,为摆脱一步溶液法对有毒反溶剂的依赖,引入低温预退火工艺,通过对预退火时间及温度、钙钛矿前驱体溶液浓度等参数的优化,在空气环境下,预退火温度为80℃、钙钛矿前驱体溶液浓度为1.6 mol/L且未使用反溶剂的条件下获得了10.52%的最佳光电转化效率,同时CsPbI_(2)Br钙钛矿的退火温度可降低至240℃,并且未封装的器件在空气环境下显示出了较好的稳定性。展开更多
Designing post-formed two-dimensional(2D)perovskite on the surface of three-dimensional(3D)perovskite with matched energy levels and high stability is crucial for improving the performance and stability of perovskite ...Designing post-formed two-dimensional(2D)perovskite on the surface of three-dimensional(3D)perovskite with matched energy levels and high stability is crucial for improving the performance and stability of perovskite solar cells(PSCs).Herein,a long alkyl chain dodecylammonium bromide(DABr)was applied to react with excessive lead iodide(PbI_(2))on the grain boundary of metal halide perovskite preferentially,forming DA_(2)PbI_(4)(n=1)to constitute a clear 2D/3D heterojunction.The existence of heterojunction increases the intensity of the built-in electric field of the device to enhance carrier separation and extraction,and the amino group of dodecylammonium cation passivates defects,which jointly contribute to the improvement of the power conversion efficiency(PCE)from 20.35 to 21.81%.The long alkyl chain endows the 2D perovskite with good hydrophobic properties,improving the humidity and thermal stability of the device.The unencapsulated device can maintain 64%of its initial efficiency after 1065 h storage in ambient air.展开更多
Morphology-controllable Cu2SnS3 thin films on solvothermal process and used in dye-sensitized solar cells as Mo-glass were prepared via a facile in situ one-step counter electrodes. The effects of different solvents ...Morphology-controllable Cu2SnS3 thin films on solvothermal process and used in dye-sensitized solar cells as Mo-glass were prepared via a facile in situ one-step counter electrodes. The effects of different solvents on the morphology of films were investigated. DSC based on the porous net-like Cu2SnS3 thin film as counter electrodes showed a power conversion efficiency of 2.30%, which was improved to 3.35% after annealing.展开更多
The application of titanium dioxide(TiO_(2))in the photovoltaic(PV)field is gaining traction as this material can be deployed in doping-free heterojunction solar cells with the role of electron selective contact.For m...The application of titanium dioxide(TiO_(2))in the photovoltaic(PV)field is gaining traction as this material can be deployed in doping-free heterojunction solar cells with the role of electron selective contact.For modeling-based optimization of such contact,knowledge of the titanium oxide defect density of states(DOS)is crucial.In this paper,we report a method to extract the defect density through nondestructive optical measures,including the contribution given by small polaron optical transitions.The presence of both related to oxygen-vacancy defects and polarons is supported by the results of optical characterizations and the evaluation of previous observations resulting in a defect band fixed at 1 eV below the conduction band edge of the oxide.Solar cells employing pulsed laser deposited-TiO_(2)electron selective contacts were fabricated and characterized.The J-V curve of these cells showed,however,an S-shape,then a detailed analysis of the reasons for such behavior was carried out.We use a model involving the series of a standard cell equivalent circuit with a Schottky junction in order to explain these atypical performances.A good matching between the experimental measurements and the adopted theoretical model was obtained.The extracted parameters are listed and analyzed to shed light on the reasons behind the low-performance cells.展开更多
In this study, we report narrow-size distribution Zn_2SnO_4（ZSO） nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer（EEL） in the inverted polymer solar ce...In this study, we report narrow-size distribution Zn_2SnO_4（ZSO） nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer（EEL） in the inverted polymer solar cells（i-PSCs）. Moreover, poly[（9,9-bis（30-（N,N-dimethylamino）propyl）-2,7-fluorene）-alt-2,7-（9,9-dioctylfluorene）]（PFN） is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis（2-ethylhexyloxyl）benzo[1,2-b：4,5-b0] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl]（PTB7） blended with（6,6）-phenyl-C_（71）-butyric acid methylester（PC_（71）BM） bulk heterojunction（BHJ） composite, exhibits a power conversion efficiency（PCE） of 8.44%, which is nearly 10% enhancement as compared with that of7.75% observed from the i-PSCs by PTB7：PC_（71）BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.展开更多
Cu2ZnSnSe4 （CZTSe） thin film solar cells have been fabricated using a one-step co-evaporation technique. The structural properties of polycrystalline CZTSe films deposited at different selenium evaporation temperatu...Cu2ZnSnSe4 （CZTSe） thin film solar cells have been fabricated using a one-step co-evaporation technique. The structural properties of polycrystalline CZTSe films deposited at different selenium evaporation temperatures （TSe） have been investigated using X-ray diffraction spectra, scanning electron microscopy, and atomic force microscopy. A relationship between TSe and the secondary phases deposited in the initial stage is established to explain the experimental observations. The Se flux is not necessarily increased too much to reduce Sn loss and the consumption of Se during fabrication could also be reduced. The best solar cell, with an efficiency of 2.32%, was obtained at a medium Tse of 230 ℃ （active area 0.34 cm2）.展开更多
We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO（AZO）/n-type oxide semiconductor/p-type Cu_2O heterojunction solar cells fabricated using p-type Cu_2O sheets pre...We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO（AZO）/n-type oxide semiconductor/p-type Cu_2O heterojunction solar cells fabricated using p-type Cu_2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu_2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu_2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa_2O_4 thin-film layer. In most of the Cu_2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO–MgO and Ga_2O_3–Al_2O_3systems, higher conversion efficiencies（á/ as well as a high open circuit voltage（Voc/ were obtained by using a relatively small amount of MgO or Al_2O_3, e.g.,（ZnO）0：91–（MgO）0：09 and（Ga_2O_3/0：975–（Al_2O_3/0：025, respectively. When Cu_2O-based heterojunction solar cells were fabricated using Al_2O_3–Ga_2O_3–MgO–ZnO（AGMZO）multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Vocof 0.98 V and an á of 4.82% were obtained. In addition, an enhanced á and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu_2O heterojunction solar cells fabricated using Na-doped Cu_2O（Cu_2O：Na） sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an á of 6.25% and a Vocof 0.84 V were obtained in a Mg F2/AZO/n-（Ga_2O_3–Al_2O_3//p-Cu_2O：Na heterojunction solar cell fabricated using a Cu_2O：Na sheet with a resistivity of approximately 10 cm and a（Ga_（0：975）A_（l0：025）/2O3 thin film with a thickness of approximately 60 nm.In addition, a Vocof 0.96 V and an á of 5.4% were obtained in a Mg F_2/AZO/n-AGMZO/p-Cu_2O：Na heterojunction solar cell.展开更多
基金supported by the National Key R&D Program of China(2019YFB1503500,2018YFB1500200,2018YEE0203400)the Natural Science Foundation of China(U1902218,11774187)the 111 project(B16027)。
文摘It is very important to understand why a small amount of alkali metal doping in Cu_(2)ZnSn(S,Se)_(4)(CZTSSe)solar cells can improve the conversion efficiency.In this work,Na-doped CZTSSe is prepared by a simple solution method,and then the effects on the surface properties of the absorber layer,the buffer layer growth,and the modifications of the solar cell performance induced by the Na doping are studied.The surface of the absorber layer is more Cu-depletion and less roughness due to the Na doping.In addition,the contact angle of the surface increases because of Na doping.As a consequence,the thickness of the CdS buffer layer is significantly reduced and the optical losses in the CdS buffer layer are decreased.The difference of quasi-Fermi levels(EFn-EFp) increases with a small amount of Na doping in the CZTSSe solar cell,so that open circuit voltage(VOC) increased significantly.This work offers new insights into the effects of Na doping on CZTSSe via a solution-based approach and provides a deeper understanding of the origin of the efficiency improvement of Na-doped CZTSSe thin film solar cells.
基金Project supported by the Ministry of Science and Technology of China (Grant No. 2011CB932802)the National Natural Science Foundation of China (Grant No. 60978060)the Beijing Municipal Science & Technology Commission,China (Grant No. Z090803044009001)
文摘The application of TiO2-based devices is mainly dependent on their crystalline structure, morphology, size, and exposed facets. Two kinds of TiO2 with different structures, namely TiO2 pompons and TiO2 nanotubes, have been prepared by the hydrothermal method. TiO2 with different structures is characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and Brunauer Emmett-Teller （BET） surface area analysis. Solar cells based on poly（3-hexylthiophene） （P3HT） and TiO2 with different structures are fabricated. In the device ITO/TiO2/P3HT/Au, the P3HT is designed to act as the electron donor, and TiO2 pompons and TiO2 nanotubes act as the electron acceptor. The effects of the TiO2 structure on the performance of hybrid heterojunction solar cells are investigated. The device with TiO2 pompons has an open circuit voltage （Voc） of 0.51 V, a short circuit current （Jsc） of 0.21 mA/cm2, and a fill factor （FF） of 28.3%. Another device with TiO2 nanotubes has a Voc of 0.5 V, Jsc of 0.27 mA/cm2, and FF of 28.4%. The results indicate that the TiO2 nanotubes with a unidimensional structure have better carrier transport and light absorption properties than TiO2 pompons. Consequently, the solar cell based on TiO2 nanotubes has a better performance.
基金Project supported by the National Natural Science Foundation of China(Grant No.51673214)the National Key Research and Development Program of China(Grant No.2017YFA0206600)。
文摘The morphology and interface of perovskite film are very important for the performance of perovskite solar cells(PSCs).The quality of perovskite film,fabricated via two-step spin-coating process,is significantly influenced by the morphology and crystallinity of PbI2 film.With the addition of additive dimethyl sulfoxide(DMSO)into the PbI2 precursor,the roughness and trap-state density of perovskite film have been significantly reduced,leading to the excellent contact between perovskite layer and subsequent deposited carrier transport layer.Accordingly,the planar heterojunction PSCs with an architecture of ITO/SnO2/perovskite/PTAA/Ag show an efficiency up to 19.02%.Furthermore,PSCs exhibit promising stability in air with a humidity of ~45%,and retain 80% of initial efficiency after being exposed to air for 400 h without any encapsulation.
基金Projects(51204214,51272292,51222403)supported by the National Natural Science Foundation of China
文摘The Cu2ZnSnS4 thin film was prepared by a facile solution method without vacuum environment and toxic substance. The formation mechanism of the film was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman scattering measurements. Through cyclic voltammetry and photo-electricity tests, the electrocatalytic activity of the prepared film as the counter electrode of dye-sensitizedsolar cell was also studied. The results show that the mixed precursor solution mainly consists of Cu2SnS3 nanoparticles and Zn ions.After 550 °C annealing process on the precursor film prepared from the mixed solution, Cu2ZnSnS4 thin film is obtained. Besides, itis found that the prepared Cu2ZnSnS4 thin film has the electrocatalytic activity toward the redox reaction of I3?/I? and the dye-sensitized solar cell with the prepared Cu2ZnSnS4 thin film as the counter electrode achieves the efficiency of 1.09%.
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.
文摘基于无机CsPbI_(2)Br的碳基无空穴传输层钙钛矿太阳能电池(carbon based hole transport material freeperovskite solar cells,C-PSCs)具有成本低、易制备和稳定性好等优点而受到广泛关注。研究了空气环境下制备高效稳定的平面异质结CsPbI_(2)Br C-PSCs的2种制备工艺。首先,通过对反溶剂材料的种类及用量、钙钛矿前驱体溶液浓度等参数的优化,在反溶剂为800μL、钙钛矿前驱体溶液浓度为1.2 mol/L的条件下,采用一步溶液法成功制备了光电转换效率为9.87%的CsPbI_(2)Br C-PSCs。其次,为摆脱一步溶液法对有毒反溶剂的依赖,引入低温预退火工艺,通过对预退火时间及温度、钙钛矿前驱体溶液浓度等参数的优化,在空气环境下,预退火温度为80℃、钙钛矿前驱体溶液浓度为1.6 mol/L且未使用反溶剂的条件下获得了10.52%的最佳光电转化效率,同时CsPbI_(2)Br钙钛矿的退火温度可降低至240℃,并且未封装的器件在空气环境下显示出了较好的稳定性。
基金the National Natural Science Foundation of China(Nos.52025028,52072254,51772197,51872191,52002258)the Natural Science Foundation of Jiangsu Province(No.BK20200877)the Key University Science Research Project of Jiangsu Province(No.21KJA430005)。
文摘Designing post-formed two-dimensional(2D)perovskite on the surface of three-dimensional(3D)perovskite with matched energy levels and high stability is crucial for improving the performance and stability of perovskite solar cells(PSCs).Herein,a long alkyl chain dodecylammonium bromide(DABr)was applied to react with excessive lead iodide(PbI_(2))on the grain boundary of metal halide perovskite preferentially,forming DA_(2)PbI_(4)(n=1)to constitute a clear 2D/3D heterojunction.The existence of heterojunction increases the intensity of the built-in electric field of the device to enhance carrier separation and extraction,and the amino group of dodecylammonium cation passivates defects,which jointly contribute to the improvement of the power conversion efficiency(PCE)from 20.35 to 21.81%.The long alkyl chain endows the 2D perovskite with good hydrophobic properties,improving the humidity and thermal stability of the device.The unencapsulated device can maintain 64%of its initial efficiency after 1065 h storage in ambient air.
基金financially supported by the National Natural Science Foundation of China (No. 21203226)
文摘Morphology-controllable Cu2SnS3 thin films on solvothermal process and used in dye-sensitized solar cells as Mo-glass were prepared via a facile in situ one-step counter electrodes. The effects of different solvents on the morphology of films were investigated. DSC based on the porous net-like Cu2SnS3 thin film as counter electrodes showed a power conversion efficiency of 2.30%, which was improved to 3.35% after annealing.
文摘The application of titanium dioxide(TiO_(2))in the photovoltaic(PV)field is gaining traction as this material can be deployed in doping-free heterojunction solar cells with the role of electron selective contact.For modeling-based optimization of such contact,knowledge of the titanium oxide defect density of states(DOS)is crucial.In this paper,we report a method to extract the defect density through nondestructive optical measures,including the contribution given by small polaron optical transitions.The presence of both related to oxygen-vacancy defects and polarons is supported by the results of optical characterizations and the evaluation of previous observations resulting in a defect band fixed at 1 eV below the conduction band edge of the oxide.Solar cells employing pulsed laser deposited-TiO_(2)electron selective contacts were fabricated and characterized.The J-V curve of these cells showed,however,an S-shape,then a detailed analysis of the reasons for such behavior was carried out.We use a model involving the series of a standard cell equivalent circuit with a Schottky junction in order to explain these atypical performances.A good matching between the experimental measurements and the adopted theoretical model was obtained.The extracted parameters are listed and analyzed to shed light on the reasons behind the low-performance cells.
基金supported by National Natural Science Foundation of China (No. 51329301)
文摘In this study, we report narrow-size distribution Zn_2SnO_4（ZSO） nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer（EEL） in the inverted polymer solar cells（i-PSCs）. Moreover, poly[（9,9-bis（30-（N,N-dimethylamino）propyl）-2,7-fluorene）-alt-2,7-（9,9-dioctylfluorene）]（PFN） is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis（2-ethylhexyloxyl）benzo[1,2-b：4,5-b0] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl]（PTB7） blended with（6,6）-phenyl-C_（71）-butyric acid methylester（PC_（71）BM） bulk heterojunction（BHJ） composite, exhibits a power conversion efficiency（PCE） of 8.44%, which is nearly 10% enhancement as compared with that of7.75% observed from the i-PSCs by PTB7：PC_（71）BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.
基金supported by the Specialized Research Fund for the PhD Program of Higher Education(No.20120031110039)
文摘Cu2ZnSnSe4 （CZTSe） thin film solar cells have been fabricated using a one-step co-evaporation technique. The structural properties of polycrystalline CZTSe films deposited at different selenium evaporation temperatures （TSe） have been investigated using X-ray diffraction spectra, scanning electron microscopy, and atomic force microscopy. A relationship between TSe and the secondary phases deposited in the initial stage is established to explain the experimental observations. The Se flux is not necessarily increased too much to reduce Sn loss and the consumption of Se during fabrication could also be reduced. The best solar cell, with an efficiency of 2.32%, was obtained at a medium Tse of 230 ℃ （active area 0.34 cm2）.
文摘We describe significant improvements of the photovoltaic properties that were achieved in Al-doped ZnO（AZO）/n-type oxide semiconductor/p-type Cu_2O heterojunction solar cells fabricated using p-type Cu_2O sheets prepared by thermally oxidizing Cu sheets. The multicomponent oxide thin film used as the n-type semiconductor layer was prepared with various chemical compositions on non-intentionally heated Cu_2O sheets under various deposition conditions using a pulsed laser deposition method. In Cu_2O-based heterojunction solar cells fabricated using various ternary compounds as the n-type oxide thin-film layer, the best photovoltaic performance was obtained with an n-ZnGa_2O_4 thin-film layer. In most of the Cu_2O-based heterojunction solar cells using multicomponent oxides composed of combinations of various binary compounds, the obtained photovoltaic properties changed gradually as the chemical composition was varied. However, with the ZnO–MgO and Ga_2O_3–Al_2O_3systems, higher conversion efficiencies（á/ as well as a high open circuit voltage（Voc/ were obtained by using a relatively small amount of MgO or Al_2O_3, e.g.,（ZnO）0：91–（MgO）0：09 and（Ga_2O_3/0：975–（Al_2O_3/0：025, respectively. When Cu_2O-based heterojunction solar cells were fabricated using Al_2O_3–Ga_2O_3–MgO–ZnO（AGMZO）multicomponent oxide thin films deposited with metal atomic ratios of 10, 60, 10 and 20 at.% for the Al, Ga, Mg and Zn, respectively, a high Vocof 0.98 V and an á of 4.82% were obtained. In addition, an enhanced á and an improved fill factor could be achieved in AZO/n-type multicomponent oxide/p-type Cu_2O heterojunction solar cells fabricated using Na-doped Cu_2O（Cu_2O：Na） sheets that featured a resistivity controlled by optimizing the post-annealing temperature and duration. Consequently, an á of 6.25% and a Vocof 0.84 V were obtained in a Mg F2/AZO/n-（Ga_2O_3–Al_2O_3//p-Cu_2O：Na heterojunction solar cell fabricated using a Cu_2O：Na sheet with a resistivity of approximately 10 cm and a（Ga_（0：975）A_（l0：025）/2O3 thin film with a thickness of approximately 60 nm.In addition, a Vocof 0.96 V and an á of 5.4% were obtained in a Mg F_2/AZO/n-AGMZO/p-Cu_2O：Na heterojunction solar cell.
