• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Micro-mechanism study of the effect of Cd-free buffer layers ZnXO(X =Mg/Sn)on the performance of flexible Cu2ZnSn(S,Se)4 solar cell

    2023-03-13 09:20:30CaixiaZhang張彩霞YalingLi李雅玲BeibeiLin林蓓蓓JianlongTang唐建龍QuanzhenSun孫全震WeihaoXie謝暐昊HuiDeng鄧輝QiaoZheng鄭巧andShuyingCheng程樹英
    Chinese Physics B 2023年2期
    關(guān)鍵詞:彩霞

    Caixia Zhang(張彩霞) Yaling Li(李雅玲) Beibei Lin(林蓓蓓) Jianlong Tang(唐建龍)Quanzhen Sun(孫全震) Weihao Xie(謝暐昊) Hui Deng(鄧輝)Qiao Zheng(鄭巧) and Shuying Cheng(程樹英)

    1College of Physics and Information Engineering,and Institute of Micro-Nano Devices and Solar Cells,Fuzhou University,Fuzhou 350108,China

    2Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering,Changzhou 213164,China

    Keywords: ZnMgO/ZnSnO,numerical simulation,Cd-free buffer,heterojunction interface

    1.Introduction

    Kesterite Cu2ZnSn(S,Se)4(CZTSSe)solar cells have the potential to replace Cu(In, Ga)(S, Se)2(CIGSSe) solar cells owing to their environmentally friendly, earth-abundant, and less-toxic constituent elements.[1]CZTSSe thin-film shows ptype conductivity,high light absorption coefficients of approximately 104cm-1,and direct bandgaps of 1.0 eV-1.5 eV.Currently, the buffer layer in a high-efficiency CZTSSe device is usually CdS with the highest efficiency up to 13%.[2]The CdS layer prepared by the chemical bath deposition (CBD)method can prevent damage to the CZTSSe layer caused by the sputtering deposition method,and Cd2+incorporation into CZTSSe can greatly reduce the surface defects of the CZTSSe layer, improving the device efficiency.However, CdS buffer layers will not be conducive to long-term commercial development due to the toxicity of Cd and the hazardous waste generated during the preparation process.And the CdS layer with a 2.4-eV bandgap can cause optical absorption loss in the short wavelength, influencing the light utilization of the CZTSSe layer and the short-circuit current density(Jsc)of the device.[3]To replace the toxic CdS buffer,several researchers are investigating Cd-free CZTSSe solar cells with high efficiencies, such as In2S3,[4]ZnO,[5]Zn (O, S),[6]Zn1-xMgxO(ZnMgO),[7]and Zn1-xSnxOy(ZnSnO).[8]

    When searching for new alternative Cd-free buffer layer materials, the focus should first be on the energy band alignment between the absorber layer and the buffer layer.The conduction band offset(CBO)between the CZTSSe absorber and the buffer layer has profound effects on the transport and collection of carriers.Among those buffers, we choose the ZnMgO or ZnSnO buffer layer with a wide bandgap and tunable bandgaps, which has the advantages of alleviating the short-wavelength optical loss and environmental protection of the elements, especially, the CBO of the heterojunction interface can be controlled by adjusting the element doping ratio.[9,10]ZnMgO and ZnSnO are ternary alloys formed by ZnO with metal oxides MgO and SnO, respectively, which may be important buffer layer candidates in CZTSSe solar cells.Liuet al.[11]investigated the electronic structure characteristics of Zn1-xMgxO alloys with different Mg components, and it is found that the band gaps in Zn1-xMgxO increase with increasing Mg composition, and the conduction band arrangement and Fermi level position are related to the Mg concentration.For Zn1-xSnxOymaterials,Guoet al.confirmed that as the Sn concentration increases, the band gap of the material changes significantly, and the O 2p orbital(valence band) and Zn 3d, 4s, and 4p (conduction band) orbitals are affected simultaneously.[12]According to these reports, ZnMgO and ZnSnO can control the interfacial CBO by regulating the Mg/(Zn+Mg)and Sn/(Zn+Sn)ratios.Several experimental studies have confirmed the feasibility of replacing the traditional CdS layer with the ZnMgO and Zn-SnO layers.Hironiwaet al.fabricated CZTSSe/ZnMgO solar cell on Mo/SLG substrates with an efficiency of 2.76%.[7,13]Kimet al.reported over 11% efficiency for CZTSSe/ Zn-SnO heterojunction cells fabricated by sputtering on Mo/SLG substrates.[8]There are few reports on flexible cadmium-free CZTSSe solar cells using Mo foil substrates.Our group focuses on the study of Mo-foil-based flexible CZTSSe solar cells.Flexible solar cells have attracted wide attention because of their ability to achieve photovoltaic building integration and wearable functions.

    For the exploration and research of solar cells, numerical simulation is one of the methods for planning and designing high-performance solar cells.In our work, the SCAPS-1D software is used to simulate the photovoltaic performance of solar cell structure Mo/CZTSSe/ZnMgO or (ZnSnO)/i-ZnO/ITO/Ag.Different concentrations of Mg or Sn doped into ZnO are investigated to form a more favorable energy band matching for optimal solar cell performance.The simulation results show that the Zn1-xMgxO and Zn1-xSnxOylayers achieve the best device efficiencies at doping concentrations (x) 0.1 and 0.2, respectively.However, the efficiency of CZTSSe/Zn0.9Mg0.1O and CZTSSe/Zn0.8Sn0.2O devices is quite different.Based on the simulation results,we also study the effects of the thickness and carrier concentration of the Cd-free buffer layers on the solar cell performance and further analyze the physical mechanism of CBO between the buffer layer and the CZTSSe absorber affecting the carrier transmission.Finally,the solar cell structure is optimized and designed by numerical simulations, flexible CZTSSe/Zn0.9Mg0.1O and CZTSSe/Zn0.8Sn0.2O heterojunction solar cells are experimentally fabricated with the optimal doping ratio, and the related tests and characterizations are performed.The doping of Mg reduces the carrier concentration and mobility of the ZnMgO buffer layer and increases the resistivity, which,as demonstrated by numerical simulations, are experimentally confirmed.As a result, the electrical conductivity of the ZnMgO layer needs to be further adjusted.Some literature reported[9,14]that ZnMgO is doped with group III elements such as Al, Ga, or In to achieve high electrical conductivity.In this study,the use of a sputtering ZnSnO layer as promising buffer layer for CZTSSe-based solar cells is demonstrated.This work provides theoretical guidance for the design and fabrication of energy-efficient CZTSSe/ZnMgO and CZTSSe/ZnSnO heterojunction solar cells.

    2.Theoretical model and experimental details

    2.1.Numerical simulation and device structure

    In this paper, the one-dimensional(1D)numerical simulation package solar cell capacitance simulator (SCAPS-1D)is mainly used to explore the effect of carrier properties and interfacial energy band alignment on CZTSSe/buffer heterojunction, which is crucial to solar cell performance.SCAPS-1D is developed by Ghent University in Belgium and is widely used to simulate solar cell devices.[15-17]SCAPS-1D is one of the numerical methods used to simulate solar cells by varying electronic parameters, cell structure,etc.to predict the effect of parameter changes on solar cell performance.The software analyzes the electrical parameters of thin film solar cells by solving Poisson’s equation, the electron continuity equation,and the hole-continuity equation at a steady state.[18]These equations are considered to be some of the fundamental semiconductor equations.Poisson’s equation is expressed as

    In this equation,φis electric potential,qis the electronic charge,ε0equals vacuum permittivity,εrstand for relative permittivity,nandpare electron and hole densities,NDandNArepresent the density of ionized donors and acceptors,ρnandρpstand for electron and hole distributions.Continuity equations for electron and hole are expressed as follows:

    The parametersJnandJpare electron and hole current densities,Gis generation rate,andRstands for recombination rate.The drift and diffusion equations for electrons and holes are represented by

    In these equations,Eis an electric field,μstands for mobility,andDis diffusivity.Equations(4)and(5)are used to describe the carrier recombination mechanisms, electric field distribution,carrier transport mechanism,etc.

    After solving Eqs.(1)-(5) above, it is possible to obtain the main parameters of the solar cell,such as open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and the power conversion efficiency(PCE).It is also possible to simulate four different measurements:I-V,C-V,C-F,andEQE.

    Figure 1 visualizes the solar cell structure of the Mo/CZTSSe/buffer layer(ZnMgO,ZnSnO)/ZnO/ITO/Ag and its band diagram as reported in the article.[19]All materials in this study are set to the uniform band gap.The work function is set to 4.5 and 5.0 for the front contact point (Ag) and the back contact point (Mo), respectively.[20,21]The relevant parameters used to perform our computations are listed in Table 1,and most input parameters for the simulations are mainly collected from relevant theories, literature, or estimated in a reasonable range,etc.[22]This numerical simulation uses the solar illumination spectrum AM 1.5 and the working temperature is set to 300 K.All numerical simulation for this work uses a surface recombination velocity of 107cm/s.We have taken ZnMgO and ZnSnO materials as alternative buffer layers and investigated the effect of the buffer layer band gap,thickness,and carrier concentration on the performance of solar cells.

    Fig.1.(a) The structure of CZTSSe-based thin-film solar cell with a ZnO-based buffer layer.(b) Diagram band structure of CZTSSe/ZnObased heterojunction.

    Table 1.Simulation parameters for the models of CZTSSe/ZnMgO and CZTSSe/ZnSnO solar cells.

    2.2.Experimental details

    2.2.1.Flexible device fabrication

    Flexible solar cells with the structure Mo foil/CZTSSe/ZnMgO/ITO or Mo foil/CZTSSe/ZnSnO/ITO(as shown in Fig.S1) are fabricated.The monomers Cu, Zn,Sn, S, and Se were added to a mixture of ethylenediamine(C2H8N2)and 1,2-ethylenedithiol(C2H6S2)in a certain proportion.The precursor solution of CZTSSe was heated and stirred in a heating set at 68°C and 700 r·min-1for 90 min until it was completely dissolved, the stabilizer solution was added, and the heating was continued for 30 min to form a homogeneous and clarified CZTSSe precursor solution.The prepared precursor solution is repeatedly spin-coated onto a flexible Mo foil substrate and pre-annealed to form a CZTSSe prefabricated layer.Then, the treated samples are selenised by rapid thermal processing.A protective gas is continuously passed throughout the selenisation process to produce CZTSSe films.The ZnMgO and ZnSnO buffer layers are prepared by magnetron sputtering.The ITO film(260 nm)is prepared by radio frequency (RF) magnetron sputtering with a sputtering power of 40 W.Finally, the Ag collection grid(~600 nm) is deposited by the thermal evaporation method.The active area for solar cells is 0.21 cm2.

    2.2.2.ZnMgO and ZnSnO film deposition

    ZnMgO or ZnSnO layers are deposited on CZTSSe absorbers as buffer layers.In the sputtering system, the back pressure (BP) is below 1×10-3Pa, while the working pressure (WP) is kept constant at 2 Pa.The ZnMgO films are prepared using a 2-inch (1 inch=2.54 cm) (ZnO:MgO=90:10 at.%) target (99.99%) sputtered in an atmosphere of argon,and ion beam power of 50 W.The ZnSnO layers are prepared using 2-inch Sn(99.99%)and ZnO(99.99%)targets.The sputtering power of Sn and ZnO is 5 W and 50 W,respectively.The thickness of buffer layer is controlled to be about 100 nm by adjusting the deposition time (as shown in Fig.S2).The films deposited with buffer layer are annealed at 200°C under air atmosphere.The schematic diagram of the method for preparing ZnMgO and ZnSnO film are shown in Fig.S3.

    2.2.3.Characterizations

    The scanning electron microscope(SEM)images are carried out using an Nova Nano SEM 450 with an energy dispersive x-ray(EDX)analyzer.The current density-voltage(J-V)curve is measured using a Keithley 2400 source meter under AM 1.5-G spectrum (100 mW/cm2).The EQE is recorded on a QTest Starion500AD system ranging from 300 nm to 1350 nm.TheC-Vcharacteristics (keithley4200) are measured by using 50 mV and 100-kHz AC excitation source with a DC bias from-1.0 V to 0.4 V.The electrochemical impedance spectroscopy(EIS)spectra are measured by an electrochemical workstation(Bio-Logic SAS,VPS)at the frequency ranging from 1 Hz to 1 MHz.A system consisting of 530-nm monochromatic light,a function generator,and an oscilloscope is used to measure transient photovoltage(TPV)and transient photocurrent(TPC).

    3.Results and discussion

    3.1.Effect of the buffer layers band gap on CZTSSe solar cell performance

    ZnMgO and ZnSnO have attracted attention because of their potential to control the CBO by varying the Mg/(Zn+Mg)and Sn/(Zn+Sn).[23]In this modeling study,we have investigated the effect of different doping concentrations of ZnMgO and ZnSnO on the performance of CZTSSe solar cells.ZnO doping with Mg or Sn elements can change the position of the conductive bands and valence bands,resulting in favorable conduction band offsets(CBO)at the heterojunction interface.The appropriate alignment of the p-type CZTSSe conduction band edge with the n-type buffer layer is one of the main strategies to enhance device performance.

    Figure 2 shows the trend ofVoc,Jsc,FF, andPCEof CZTSSe/ZnMgO heterojunction solar cells as the Mg doping concentration varies from 0 to 0.175.For the Zn1-xMgxO buffer layer, the bandgap can be expressed as a function ofxby the following equation:[18]

    Fig.2.(a)-(d)Influence of the Mg concentration on the performance of CZTSSe/Zn1-xMgxO heterojunction.

    Fig.3.(a)-(d)Influence of the Sn concentration on the performance of CZTSSe/Zn1-xSnxO heterojunction.

    When the doping concentration of the ZnMgO buffer layer is in the range from 0 to 0.175, the band gap varies from 3.37 eV to 4.0 eV.These simulations show that the best performance of the CZTSSe/Zn1-xMgxO heterojunction can be achieved when the Mg doping concentration is 0.1, theVoc,Jsc, andFFare 461 mV, 30.25 mA/cm2, and 64.09%,respectively, and the conversion efficiency reaches the maximum 8.93%.For the CZTSSe/ZnSnO heterojunction structure, the Sn doping concentrations are chosen to be 0, 0.13,0.18,0.2,0.31,and 1.0 according to the ZnSnO experimental data reported by Saadatet al.[24,25]The device performance of the CZTSSe/ZnSnO heterojunction reaches a maximum atx=0.2.The results are shown in Fig.3.The best solar cell performance is obtained when the Sn doping concentration reaches 0.2,with an efficiency of 11.3%(Vocof 476 mV,Jscof 34.72 mA/cm2,andFFof 68.38%).

    From the numerical simulation results,the improved efficiency of the CZTSSe/ZnMgO and CZTSSe/ZnSnO devices is mainly attributed to the improvedVocandJsc.While the improvement inVocandJsccan be attributed to the suppression of recombination at the CZTSSe/ZnMgO and CZTSSe/ZnSnO heterojunction interface by the appropriate energy band alignment.Furthermore, It is observed that theJscof Zn0.8Sn0.2O (34.72 mA/cm2) is superior to that of Zn0.9Mg0.1O (30.25 mA/cm2) because the reduction of Zn0.8Sn0.2O interfacial recombination can significantly improve theEQE, especially in the short wavelength ranging from 400 nm to 1000 nm (see Fig.S3).This phenomenon is also confirmed in the experimental section.As can be observed in Figs.2 and 3, when the doping concentration of ZnMgO and ZnSnO increases, the efficiency of CZTSSe solar cells increases first and then decreases.This indicates that the CZTSSe/ZnMgO and CZTSSe/ZnSnO heterojunction devices can achieve optimum performance by varying the Mg/(Zn+Mg) and Sn/(Zn+Sn) ratios.Next, we will explain the changing trend of CZTSSe solar cell performance with the band gap of ZnMgO and ZnSnO from the perspective of energy band alignment.

    To understand the effect of the conduction band offsets(CBO)on solar cell performance,in the SCAPS-1D software,we choose the “electron affinity rule” (Schottky limit) to directly reflect energy band alignment.[26]The“electron affinity rule”is a way of aligning the bulk model of a semiconductor according to the distanceχ(affinity energy)between the conduction band and the vacuum level of the semiconductor.The model does not take into account Fermi level pinning(which tends to decrease the CBO)and chemical interdiffusion(which tends to increase the CBO).[26]Equation(7)is a calculation of the“ideal”interfacial energy band bias without consideration of Fermi level pinning and interfacial polarization

    whereχaandχbare the electron affinity of absorber and buffer layer,φCNL,aandφCNL,bare the charge neutrality level of absorber and buffer layer,The dimensionless screening parameterSis a bulk property of the wider bandgap semiconductor.In Eq.(7)S=1 for the electron affinity rule,it can be simplified to the following equation:

    To further analyze the intrinsic causes and mechanisms of the effect of CBO on the performance of CZTSSe devices,we plot the interface band diagrams of(a)CZTSSe/ZnO(x=0),(b)CZTSSe/Zn0.9Mg0.1O,and(c)CZTSSe/Zn0.825Mg0.175O heterojunction, as shown in Fig.4.As the doping concentration of Mg is increased from 0 to 0.1, the energy band alignment at the CZTSSe/buffer heterojunction interface changes from the“cliff”-type to the more favorable“spike”-type.However,when Mg element content further increases up to 0.175,there is a large spike at the heterojunction interface,as shown in Fig.4(c), which is like an electron barrier to impede the carrier transport.Figure 5 shows the different types of energy band alignment formed by the CZTSSe absorption layer with ZnO (x=0), ZnSnO (x=0.2), and SnO buffer layers at the interface,respectively.When the Sn doping concentration (x) increases from 0 to 0.2, the energy band alignment changes from a “cliff” type to a flat “spike” type band interface.The“spike”type band is more conducive to carrier transport than the “cliff”-like energy band alignment.Figure 5(c)shows the formation of an oversized “cliff” type CBO at the CZTSSe/SnO interface, which reduces the cell performance from 11.3%to 9.3%.

    Fig.4.Band diagrams of CZTSSe with(a)ZnO(x=0);(b)ZnMgO(x=0.10);(c)ZnMgO(x=0.175).

    Fig.5.Band diagrams of CZTSSe with(a)ZnO(x=0);(b)ZnSnO(x=0.20);(c)SnO buffer layer.

    Band alignment at CZTSSe/buffer interface has a profound effect on the performance of solar cells.The conduction band offset at the heterojunction interface can be divided into two types: cliff-like and spike-like band alignments.From the analysis of Figs.4 and 5, we can note that the CZTSSe/buffer (ZnO or SnO) shows the “cliff”-like energy level alignment because the conduction band minimum of the CZTSSe absorber is more than that of the buffer layer.Therefore, the activation energy of interface recombination(EA) is lower than the band gap of CZTSSe and leads to the interface recombination dominant path.[23]The occurrence of interface recombination results in poor overall device performance as shown in Fig.2 (x=0) and Fig.3 (x=0, 1).As CZTSSe solar cells feature numerous defect states at the interface, particularly deep defect states.After charge separation under forwarding bias, electrons and holes build up and cause severe charge recombination through deep energy level defects at the heterojunction interface with a cliff-like type.The better band alignment in Fig.4(b)CZTSSe/Zn0.9Mg0.1O and Fig.5(b) CZTSSe/Zn0.8Sn0.2O interface shows a small spike-like CBO (+0.05 eV) or an almost “flat” spike band favorable to minority carrier transport and collection.This is why Fig.2 Zn1-xMgxO (x=0.1) and Fig.3 Zn1-xSnxO(x=0.2) achieve the best device efficiency.When the spike structure is formed at the interface,the interface level structure can further create a slight barrier to prevent interface recombination.However,when the spiky conduction band offset exceeds a suitable range(0 eV-0.3 eV),it will create a substantial obstacle to blocking electron transport.The results confirm that the band conduction offset of CZTSSe/Zn1-xMgxO and CZTSSe/Zn1-xSnxO can be controlled by varying the Mg/(Zn+Mg)and Sn/(Zn+Sn).Energy band alignment at the heterojunction interface is a key factor when selecting materials to replace toxic CdS buffer layers.

    On the other hand,it is observed from Figs.4 and 5 that the difference in device performance between the Zn1-xMgxO and Zn1-xSnxO as buffer layers is great, although the doping concentration of the two is at the optimal valuesx=0.1 and 0.2, respectively.This suggests that in addition to focusing on the energy band alignment of the interface, other factors should also be considered when selecting a suitable cadmiumfree buffer layer.The following simulation will investigate the effect of carrier concentration and thickness of Zn0.9Mg0.1O and Zn0.8Sn0.2O layers on device performance.

    3.2.Effect of buffer layer carrier concentration and thickness on CZTSSe solar cell performance

    The heterojunction interface formed by the buffer and the absorber layers plays a crucial role in the collection and transport of photogenerated charge carriers,so the buffer layer carrier concentration and thickness that affect the interface performance are important parameters.The carrier concentration and thickness of the Zn0.9Mg0.1O buffer layer vary between 1015cm-3and 1018cm-3and 30 nm-150 nm respectively,then,so the efficiency of the CZTSSe/Zn0.9Mg0.1O solar cells varies from 3.04% to 11.18%, as shown in Fig.6.It is observed from Fig.6 thatJsc,FF,andPCEare almost independent of the buffer thickness when the carrier concentration is more than 1017cm-3.However, when the concentration of Zn0.9Mg.1O carrier is less than 1016cm-3, the performance of the device decreases with the increasing thickness of the Zn0.9Mg0.1O buffer layer rises.

    Therefore, choosing a proper buffer layer thickness can improve the deterioration of cell performance.When the carrier concentration is less than 1016cm-3,the resistivity of the Zn0.9Mg0.1O layer increases, thus the thicker thickness will further reduce the performance of the device.

    Fig.6.Contour plot of the effect of the thickness and carrier concentration of the ZnMgO buffer layer on the performance parameters of CZTSSe solar cells.

    Figure 7 investigates the effect of the carrier concentration and thickness of the Zn0.8Sn0.2O layer on device performance.The carrier concentration and thickness of the ZnSnO buffer layer vary from 1017cm-3to 1020cm-3and 30 nm to 150 nm,respectively.It is observed that the solar cell performance deteriorate seriously when the carrier concentration is less than 1018cm-3and the layer thickness is less than 50 nm.And when the Zn0.8Sn0.2O layer is thinner than 45 nm with the carrier concentration is 1017cm-3,the performance of the device is only 10.49%.However,when the carrier concentration is more than 1019cm-3and the thickness is less than 60 nm,the highest device efficiency is up to 11.31%.The performance of the CZTSSe/Zn0.9Mg0.1O solar cells in Fig.6 varies very significantly with the carrier concentration and thickness of the Zn0.9Mg0.1O buffer layer(PCEfrom 3.04%to 11.18%),which is due to the low Zn0.9Mg0.1O carrier concentration and the corresponding rapidly increasing resistivity, resulting in poor device performance.Therefore, the performance of the device composed of a buffer layer with low carrier concentration is more susceptible to the buffer layer thickness.Besides, the height of the interface barrier between the absorber layer and the buffer layer is affected by the buffer carrier concentration.[27]When the carrier concentration is low,the electron Fermi level is far away from the conduction band,and the interface barrier height increases significantly.For the Zn0.8Sn0.2O buffer layer, the relatively high carrier concentration saturates the device performance,thus the buffer layer thickness has relatively little effect on the performance.

    As can be seen from Figs.6 and 7, the optimum device performance can be obtained for the Zn0.9Mg0.1O and the Zn0.8Sn0.2O buffer layer with a higher carrier concentration.For ZnMgO, Mg doping (Mg content fromx=0.1 to 0.3) reduces the carrier concentration and mobility, resulting in a low conductivity of ZnMgO.This result is confirmed in the study of ZnMgO by Ginleyet al.[9]However, according to Deepak, the carrier concentration of ZnO:Sn films deposited under a high vacuum can reach the order of 1019cm-3or even higher.[28]This is why we chose 1017cm-3and 1019cm-3as the carrier concentrations for Zn0.9Mg0.1O and Zn0.8Sn0.2O, respectively.When the carrier concentration of Zn0.9Mg0.1O is 1017cm-3, the effect of thickness on device performance is not significant.While at a carrier concentration of 1019cm-3for Zn0.8Sn0.2O, it can be seen that a thinner thickness gives better device performance.However,the buffer layer is hardly controlled experimentally when the thickness is less than 50 nm.To ensure that the thickness of the buffer layer does not cause a loss of light absorption,and that its thickness is strong enough to diffuse the photogenerated carriers outside the depletion zone,this requires determining a suitable threshold thickness.[18]

    Fig.7.Contour plot of the effect of the thickness of the ZnSnO buffer layer and carrier concentration on the performance parameters of CZTSSe solar cells.

    3.3.Effect of buffer layer thickness on CZTSSe solar cell performance

    The thickness and carrier concentration of the buffer layer are the key parameters to be considered when selecting an alternative buffer layer material.They influence the transport and collection of the photogenerated carrier.To further optimize the buffer layer thickness, we investigate the effect of the cadmium-free buffer layer thickness on the device performance, as shown in Fig.8, where the thickness of the buffer layers Zn0.9Mg0.1O and Zn0.2Sn0.8O is increased from 30 nm to 150 nm.

    For the Zn0.9Mg0.1O layer,the device performance is significantly improved when the thickness increases from 30 nm to 80 nm,the open circuit voltage(Voc)increases sharply from 402 mV to 467 mV and the short circuit current(Jsc)increases from 29.25 mA/cm2to 30.95 mA/cm2, both of which reach saturation at a thickness of 80 nm.For the Zn0.9Mg0.1O layers with low carrier concentration, the thinner thickness cannot provide the width of the depletion region required for carrier transport, resulting in carrier recombination at the interface.Moreover, the Zn0.9Mg0.1O layer with low carrier concentration has low resistivity that hinders the transport of the carriers, which have been recombined even before reaching the Ag electrode, so that the device performance decreases when the buffer layer thickness is greater than 120 nm, especially theFF.We chose 80 nm as the optimum thickness for the Zn0.9Mg0.1O buffer layer.For the Zn0.2Sn0.8O,Voc,Jsc, andPCEshow a similar trend, with a slight reduction at a thickness greater than 80 nm,while theFFincreased slightly after 80 nm.This means that the Zn0.2Sn0.8O layer with high carrier concentration has high conductivity, and the carrier transport and collection are less affected by the thickness.But it causes some light absorption loss when the buffer layer thickness is greater than 80 nm.Based on the above studies of the carrier concentration and thickness,we chose 80 nm as the thickness of the Zn0.2Sn0.8O buffer layer.

    Fig.8.Open circuit voltage(Voc)and short circuit current(Jsc)as a function of(a)Zn0.9Mg0.1O and(b)Zn0.8Sn0.2O thicknesses; fill factor(FF)and efficiency(PCE)as a function of(c)Zn0.9Mg0.1O and(d)Zn0.8Sn0.2O thicknesses.

    Fig.9.(a) Current density-voltage curves and (b) EQE curve of the CZTSSe solar cells with different buffer layers Zn0.9Mg0.1O and Zn0.8Sn0.2O obtained by SCAPS simulation.

    Based on the optimal stimulation parameters,figures 9(a)and 9(b) show the comparison of theJ-Vcharacteristics and the EQE responses between the CZTSSe/Zn0.9Mg0.1O and CZTSSe/Zn0.2Sn0.8O devices,respectively.From the SCAPS simulation results, for the CZTSSe/Zn0.9Mg0.1O solar cell,thePCEof the solar cell with a thickness of 80 nm (optimal value) is 9.44% with a carrier concentration of 1017cm-3in the Zn0.9Mg0.1O buffer layer.For the CZTSSe/ Zn0.8Sn0.2O solar cell, thePCEof the solar cell with a thickness of 80-nm optimal value) is 11.28% with a carrier concentration of 1019cm-3in the Zn0.8Sn0.2O buffer layer.The ZnMgO band gap is higher than the ZnSnO layer, but the spectral response becomes worse at short wavelengths(Fig.9(b)),which may be due to the reduced carrier collection.In this study,we discover that thickness has less impact on the buffer layers with high carrier concentration(ZnSnO),and the buffer layers with low carrier concentration(ZnMgO)had significantly worse performance (VocandJsc) due to deterioration of carrier transport properties.The simulation results show that the ZnSnO buffer layer is more suitable as an alternative buffer layer, while the ZnMgO material has limitations due to its material properties.

    3.4.Experimentally fabricated CZTSSe/ZnMgO (or Zn-SnO)heterojunction solar cells

    Figures 10(a)-10(b) showJ-Vcurves and EQE spectra of CZTSSe/Zn0.8Sn0.2O and CZTSSe/Zn0.9Mg0.1O solar cells.The ratios of Mg/(Zn+Mg) and Sn/(Zn+Sn) prepared by sputtering are 0.1 and 0.2, respectively, as measured by EDX(see Fig.S4).Table 2 lists the performances of the solar cell (Voc,Jsc,FF, andPCE).The best CZTSSe/Zn0.8Sn0.2O devices achieve an efficiency of 7.58%, which is larger than that of the best CZTSSe/Zn0.9Mg0.1O devices(3.26%),mainly in theJscandFF.Hironiwaet al.reported CZTSSe/ZnMgO device efficiency of 2.75%on a rigid substrate,with the lowJsc(12 mA/cm2)being the key factor limiting its performance improvement.Since the conductivity of the Mg-doped ZnO layer is adversely reduced,the mobility is also significantly reduced,and the device performance is reflected in the smallerFFand the lowerJsc.The CZTSSe/Zn0.8Sn0.2O devices yield a higherJscthan the CZTSSe/Zn0.9Mg0.1O device,which is mainly due to higher absorption in the short wavelength range as can be seen in the external quantum efficiency (EQE) curves shown in Fig.10(b).

    Fig.10.(a) The J-V curves under standard AM 1.5 illumination; (b) external quantum efficiency (EQE); (c) d(EQE)/d(λ) curves for CZTSSe/Zn0.8Sn0.2O and CZTSSe/Zn0.9Mg0.1O devices.(d) Nyquist plot of devices with the equivalent electrical circuit model.(e) TPV decay and(f)TPC decay of typical devices.

    Table 2.The device parameters derived from J-V curves.

    The ZnMgO and ZnSnO buffer layers effectively improve the optical absorption loss caused by the traditional CdS layer in the short wavelength band.The band gaps of different layers in the device can be obtained byEQEcurves calculation.The band gaps of the absorber layer in the CZTSSe/Zn0.8Sn0.2O and CZTSSe/Zn0.9Mg0.1O devices are 1.09 eV and 1.06 eV, respectively, and the smaller band gap of CZTSSe/ Zn0.9Mg0.1O device may be due to the diffusion of Mg into the absorber layer.The narrowing of the band gap of the absorber layer leads to a smallerVocof CZTSSe/Zn0.9Mg0.1O devices (360 mV) than CZTSSe/Zn0.8Sn0.2O (397 mV) devices.[29]We calculate the diode parameters of the device through theJ-Vcurve,and the specific formula is as follows:[30]

    whereAis the ideality factor,Rsis series resistance,andGshis shunt conductance,JLandJ0are the photocurrent and reverse saturation current density,respectively.

    The conductivity of the Zn0.9Mg0.1O layer decreases due to the doping of Mg, makingRs(6.87 Ω/cm2) andGsh(24.92 mS/cm2) increase, while the Zn0.8Sn0.2O layer has a relatively high carrier concentration and high conductivity,reducingRs(0.33 Ω/cm2)andGsh(6.39 mS/cm2).Jscis mainly affected byRsandGsh, so theJscof the Zn0.9Mg0.1O device is smaller than that of the Zn0.8Sn0.2O device in both theoretical simulations and experiments.As shown in Table 3,Gsh,A,andJare associated with the recombination in the depletion zone of the heterojunction interface, indicating that the heterojunction quality formed by Zn0.9Mg0.1O is worse than that formed by Zn0.8Sn0.2O.By using the SCAPS-1D simulation,we find that the carrier concentration has a significant effect on the device performance.

    To investigate the carrier transport and recombination properties of CZTSSe/Zn0.8Sn0.2O and CZTSSe/Zn0.9Mg0.1O heterojunction devices,EIS,TPC,and TPV measurements are performed.The EIS impedance diagram is obtained by fitting the simple equivalent circuit model in Fig.10(d).The equivalent circuit model consists of a resistorRsin series,a resistorRjand capacitorCein parallel.The diameter of the semicircle in the impedance diagram is equal to the value of the recombination resistanceRj.[31]From the EIS spectra(Fig.10(d)),it is clear that CZTSSe/Zn0.8Sn0.2O device shows higherRjvalues compared to the CZTSSe/Zn0.9Mg0.1O device, which means that the interface recombination of CZTSSe/Zn0.8Sn0.2O heterojunction device is less.This is further proven by the TPV and TPC measurements of the heterojunction quality.A charge recombination lifetime value (τr) can be obtained from TPV measurements in Fig.10(e), which is used to characterize the charge recombination and defect density in the solar cell.The CZTSSe/Zn0.9Mg0.1O device shows a smaller charge recombination lifetime (τr= 140 μs) than CZTSSe/Zn0.8Sn0.2O device (τr=360 μs), which also confirms that the CZTSSe/Zn0.9Mg0.1O heterojunction has a large defect density and severe interfacial recombination, resulting in a lowJscandFF.The charge transfer lifetimes (τt) of the CZTSSe/Zn0.8Sn0.2O devices and CZTSSe/Zn0.9Mg0.1O devices measured at the condition of the short circuit are shown in Fig.10(f).Theτtcharacterizes the ability of the device to extract and transfer charges.It can be seen that the CZTSSe/Zn0.8Sn0.2O devices(4μs)decay faster than the CZTSSe/Zn0.9Mg0.1O devices(8.8μs).This indicates that the charge extraction and transport of the CZTSSe/Zn0.8Sn0.2O device are better than that of the CZTSSe/Zn0.9Mg0.1O device, which is one of the reasons for the higherJscof CZTSSe/Zn0.8Sn0.2O device.From the TPC,TPV,and EIS,it is shown that the CZTSSe/Zn0.9Mg0.1O device has severe interfacial charge recombination and poor charge extraction and transport,which is in agreement with the previous theoretical simulations.

    In order to further investigate the band bending of CZTSSe/Zn0.9Mg0.1O and CZTSSe/Zn0.8Sn0.2O devices,capacitance-voltage(C-V)measurements are performed(see Fig.S5).[32]The carrier concentration in the absorber layer(Nc-v),depletion width(Wd),and built-in voltage(Vbi)can be calculated from theC-Vcurve, as shown in Table 3.After the photogenerated electron-hole pairs reach the depletion region, they are collected by electrodes under the separation of the built-in electric field.It can be seen that the wider the width of the depletion region, the more the separated electron-hole pairs, and the larger the photocurrent that is generated.TheVbiandWdof the CZTSSe/Zn0.8Sn0.2O device (0.410 V and 0.181 μm) are higher than that of the CZTSSe/Zn0.9Mg0.1O device (0.233 V and 0.104 μm).This is consistent with the higherVoc,FF, andJscobtained by the CZTSSe/Zn0.8Sn0.2O device in numerical simulations of the experimental results,indicating that Zn0.8Sn0.2O material may be a promising and inexpensive buffer layer alternative to CdS.

    Table 3.The device parameters derived from J-V curves and C-V curves.

    4.Conclusions

    In conclusion, we used numerical modeling and experimental results to examine the potential of the widebandgap non-toxic materials ZnMgO and ZnSnO as alternative buffer layers.To investigate the impacts of interfacial CBO, carrier concentration, and thickness on device performance, SCAPS modeling of ZnO-based buffer layer devices is carried out.The simulation results show that the best device performance is obtained for CZTSSe/Zn0.9Mg0.1O and CZTSSe/Zn0.8Sn0.2O devices.This is due to the small“spikelike” CBO (+0.05 eV) or almost “flat band” formed at the heterojunction interface of these two devices that facilitate the transport and collection of minority carriers.It is observed that the Zn0.8Sn0.2O devices with high carrier concentration obtain more than 11%PCEwith a small effect of thickness on device performance.The Zn0.9Mg0.1O devices display inferiorPCE.For Zn0.9Mg0.1O material, Mg doping causes a decrease in carrier concentration and an increase in resistivity.It further leads to inefficient carrier transport and increased interfacial recombination.Our experimental results show that the devicePCEvalues of the Zn0.9Mg0.1O and Zn0.8Sn0.2O thin films prepared by sputtering as buffer layers are 3.26% (the most efficient flexible CZTSSe/ZnMgO solar cells currently available)and 7.58%,respectively.The simulation results indicate that the Zn0.9Mg0.1O material has largeGshandRs, resulting in reducedJscandFF.It is further supported by our experimental data.The poor quality of the CZTSSe/Zn0.9Mg0.1O PN junction can also be confirmed byC-V, EIS, TPV, and TPC.Through both numerical simulations and experimental tests,it is proved that the ZnSnO buffer layer has the potential to replace the toxic CdS layer.The process of preparing ZnSnO by the sputtering method is more suitable for large-scale commercial development.We believe that further optimization of the cadmium-free buffer layer production process can greatly improve the efficiency of environmentally friendly kesterite solar cells.

    Acknowledgements

    Project supported by the National Natural Science Foundation of China (Grant Nos.62074037 and 52002073) and the Fund from the Fujian Science & Technology Innovation Laboratory for Optoelectronic Information of China (Grant No.2021ZZ124).The authors also thank Testing Center of Fuzhou University for facility access.

    猜你喜歡
    彩霞
    《流失》之《歲月》國畫
    沒有愛不能到達的地方
    做人與處世(2022年4期)2022-05-26 21:50:38
    Time-Consistent Investment and Reinsurance Problems for Mean-Variance Insurers with Default Risk Under Variance Premium Principle
    《云岡石窟》油畫 張彩霞
    安其的田地
    清而不俗 妍而不媚 馮彩霞制蓮子壺
    Frequency-SPeed Control Model Identification of Ultrasonic Motor Using SteP ResPonse
    繞轉(zhuǎn)小舌頭
    Graphene Based Electrochemical Sensor for the Detection of Volatile Organic Compounds
    A Teaching Plan for Lesson 3, Unit 16
    日韩大码丰满熟妇| 久久久国产欧美日韩av| 高清黄色对白视频在线免费看| 你懂的网址亚洲精品在线观看| 久久人妻福利社区极品人妻图片 | 国产精品三级大全| 啦啦啦在线观看免费高清www| www.精华液| 亚洲精品久久午夜乱码| 脱女人内裤的视频| 亚洲欧洲精品一区二区精品久久久| 男女边吃奶边做爰视频| 又粗又硬又长又爽又黄的视频| 高清av免费在线| 成人三级做爰电影| 日韩av免费高清视频| 各种免费的搞黄视频| 在线av久久热| www.精华液| 成人18禁高潮啪啪吃奶动态图| 高潮久久久久久久久久久不卡| 国精品久久久久久国模美| www.熟女人妻精品国产| 99热全是精品| 亚洲男人天堂网一区| 99国产精品一区二区蜜桃av | 国产亚洲av片在线观看秒播厂| 国产三级黄色录像| 午夜老司机福利片| 国精品久久久久久国模美| 超碰97精品在线观看| 久久天堂一区二区三区四区| 大香蕉久久成人网| 校园人妻丝袜中文字幕| 亚洲国产成人一精品久久久| 视频区欧美日本亚洲| 亚洲一卡2卡3卡4卡5卡精品中文| 啦啦啦视频在线资源免费观看| 黄网站色视频无遮挡免费观看| 精品人妻在线不人妻| 国产成人精品无人区| 国产成人欧美在线观看 | 天天操日日干夜夜撸| 18禁裸乳无遮挡动漫免费视频| 女人爽到高潮嗷嗷叫在线视频| 中文字幕亚洲精品专区| 国产男女超爽视频在线观看| 亚洲国产av新网站| 久久精品亚洲熟妇少妇任你| 精品一品国产午夜福利视频| 伊人亚洲综合成人网| 啦啦啦在线观看免费高清www| 热99国产精品久久久久久7| 涩涩av久久男人的天堂| 亚洲七黄色美女视频| 日韩大片免费观看网站| 超碰成人久久| 成人午夜精彩视频在线观看| 国产黄频视频在线观看| 国精品久久久久久国模美| 纯流量卡能插随身wifi吗| 亚洲精品美女久久av网站| 后天国语完整版免费观看| 丰满迷人的少妇在线观看| 亚洲精品日本国产第一区| 男女午夜视频在线观看| 国产成人精品久久久久久| 一本色道久久久久久精品综合| 欧美乱码精品一区二区三区| 亚洲欧美色中文字幕在线| 免费观看av网站的网址| 国产亚洲欧美精品永久| 亚洲午夜精品一区,二区,三区| 一区福利在线观看| 电影成人av| 超碰成人久久| 国产xxxxx性猛交| 欧美xxⅹ黑人| 99热国产这里只有精品6| e午夜精品久久久久久久| 精品一区二区三区四区五区乱码 | 久久ye,这里只有精品| 男女高潮啪啪啪动态图| 成人18禁高潮啪啪吃奶动态图| av网站在线播放免费| 欧美另类一区| 日本wwww免费看| 国产精品一区二区在线不卡| 久久精品久久精品一区二区三区| 中文字幕精品免费在线观看视频| 五月天丁香电影| 久久国产精品影院| 韩国精品一区二区三区| 午夜影院在线不卡| 男女床上黄色一级片免费看| av网站免费在线观看视频| 亚洲一卡2卡3卡4卡5卡精品中文| 久久久久久亚洲精品国产蜜桃av| 国产一区亚洲一区在线观看| 50天的宝宝边吃奶边哭怎么回事| 天天躁日日躁夜夜躁夜夜| 免费看av在线观看网站| 黄色 视频免费看| 十八禁高潮呻吟视频| 丰满饥渴人妻一区二区三| 亚洲国产成人一精品久久久| 婷婷色av中文字幕| h视频一区二区三区| 精品少妇黑人巨大在线播放| 叶爱在线成人免费视频播放| 欧美激情高清一区二区三区| 国产福利在线免费观看视频| 成在线人永久免费视频| 欧美精品av麻豆av| 少妇人妻久久综合中文| cao死你这个sao货| 丝袜人妻中文字幕| 成年人黄色毛片网站| 十分钟在线观看高清视频www| 大码成人一级视频| 国产精品一区二区在线不卡| 中文字幕高清在线视频| 下体分泌物呈黄色| 亚洲精品国产av蜜桃| 亚洲第一青青草原| 性高湖久久久久久久久免费观看| 国产福利在线免费观看视频| 日韩伦理黄色片| 国产精品三级大全| 好男人视频免费观看在线| 精品久久久精品久久久| 人妻人人澡人人爽人人| 久久久精品区二区三区| 波多野结衣av一区二区av| 尾随美女入室| 纵有疾风起免费观看全集完整版| 免费在线观看黄色视频的| 一级片'在线观看视频| 丝袜美足系列| 亚洲三区欧美一区| 日韩 欧美 亚洲 中文字幕| 亚洲久久久国产精品| 日本a在线网址| 99热国产这里只有精品6| www.熟女人妻精品国产| 美国免费a级毛片| 亚洲 欧美一区二区三区| 亚洲中文日韩欧美视频| 五月天丁香电影| 伊人久久大香线蕉亚洲五| 亚洲男人天堂网一区| 人成视频在线观看免费观看| 久久这里只有精品19| 国产激情久久老熟女| 国语对白做爰xxxⅹ性视频网站| 少妇粗大呻吟视频| 无遮挡黄片免费观看| 一本一本久久a久久精品综合妖精| 精品免费久久久久久久清纯 | 夫妻性生交免费视频一级片| 国产成人精品久久二区二区91| 菩萨蛮人人尽说江南好唐韦庄| 青青草视频在线视频观看| 性色av一级| 18禁国产床啪视频网站| 99国产综合亚洲精品| 18禁裸乳无遮挡动漫免费视频| 欧美日韩精品网址| 十八禁网站网址无遮挡| 日韩大码丰满熟妇| 亚洲欧洲精品一区二区精品久久久| 国产1区2区3区精品| 丁香六月欧美| 国产亚洲av高清不卡| 精品视频人人做人人爽| 亚洲人成77777在线视频| 欧美精品一区二区免费开放| 亚洲国产av新网站| 一级毛片电影观看| 91九色精品人成在线观看| 99热全是精品| 国产野战对白在线观看| 日韩,欧美,国产一区二区三区| 中文字幕亚洲精品专区| 啦啦啦啦在线视频资源| 在线观看免费视频网站a站| 欧美精品亚洲一区二区| 在线观看免费午夜福利视频| 在线观看免费午夜福利视频| 一边亲一边摸免费视频| 午夜免费鲁丝| 热99国产精品久久久久久7| 蜜桃国产av成人99| 亚洲欧美一区二区三区国产| 中文字幕制服av| 性高湖久久久久久久久免费观看| 亚洲欧美成人综合另类久久久| 欧美大码av| 男人爽女人下面视频在线观看| 欧美av亚洲av综合av国产av| 蜜桃在线观看..| 精品久久久久久久毛片微露脸 | 丝袜喷水一区| 国产欧美日韩精品亚洲av| 日韩一卡2卡3卡4卡2021年| 亚洲一区中文字幕在线| 在线精品无人区一区二区三| 一本色道久久久久久精品综合| 国产精品一二三区在线看| 成人免费观看视频高清| 亚洲欧美成人综合另类久久久| 中文字幕av电影在线播放| www日本在线高清视频| 每晚都被弄得嗷嗷叫到高潮| 在线观看人妻少妇| 人人妻人人爽人人添夜夜欢视频| 日韩av不卡免费在线播放| 亚洲国产欧美在线一区| av不卡在线播放| 人人妻,人人澡人人爽秒播 | 这个男人来自地球电影免费观看| 黄色片一级片一级黄色片| 国产1区2区3区精品| 欧美人与性动交α欧美软件| 久久久久国产精品人妻一区二区| 青春草视频在线免费观看| 最新的欧美精品一区二区| 777米奇影视久久| www日本在线高清视频| 一区福利在线观看| 国产成人精品无人区| 一级毛片 在线播放| 亚洲精品久久午夜乱码| 纯流量卡能插随身wifi吗| 国产欧美亚洲国产| 麻豆国产av国片精品| 50天的宝宝边吃奶边哭怎么回事| 亚洲精品成人av观看孕妇| 午夜福利乱码中文字幕| 肉色欧美久久久久久久蜜桃| 爱豆传媒免费全集在线观看| 国产在视频线精品| 国产xxxxx性猛交| 国产成人精品久久二区二区91| 大片电影免费在线观看免费| 女性被躁到高潮视频| 99国产精品免费福利视频| 成人三级做爰电影| 在线观看人妻少妇| 亚洲av成人精品一二三区| 亚洲欧美日韩另类电影网站| 欧美xxⅹ黑人| 真人做人爱边吃奶动态| 亚洲精品美女久久久久99蜜臀 | 国产免费又黄又爽又色| 亚洲欧洲国产日韩| 晚上一个人看的免费电影| 男的添女的下面高潮视频| 真人做人爱边吃奶动态| 捣出白浆h1v1| 夫妻午夜视频| 亚洲国产精品国产精品| 69精品国产乱码久久久| 亚洲欧美精品综合一区二区三区| 色网站视频免费| 91老司机精品| 久久亚洲国产成人精品v| 首页视频小说图片口味搜索 | 欧美黄色淫秽网站| 999久久久国产精品视频| 久久天躁狠狠躁夜夜2o2o | 久久久久精品人妻al黑| 欧美 日韩 精品 国产| 热re99久久国产66热| 精品少妇一区二区三区视频日本电影| 国产免费又黄又爽又色| 成人亚洲欧美一区二区av| 大片电影免费在线观看免费| 亚洲国产最新在线播放| 极品少妇高潮喷水抽搐| 看免费成人av毛片| 亚洲av成人精品一二三区| 精品一区二区三区av网在线观看 | 国产亚洲av片在线观看秒播厂| www.av在线官网国产| 超色免费av| 日韩免费高清中文字幕av| h视频一区二区三区| 1024香蕉在线观看| 亚洲成av片中文字幕在线观看| 久久九九热精品免费| 啦啦啦视频在线资源免费观看| 黑人巨大精品欧美一区二区蜜桃| 国产主播在线观看一区二区 | 日韩免费高清中文字幕av| 一个人免费看片子| 精品福利永久在线观看| 久久久久精品国产欧美久久久 | 一二三四在线观看免费中文在| 国产真人三级小视频在线观看| 男女下面插进去视频免费观看| 免费av中文字幕在线| 无限看片的www在线观看| 少妇精品久久久久久久| 99香蕉大伊视频| 中文字幕av电影在线播放| 日韩av免费高清视频| 黄色毛片三级朝国网站| 在线亚洲精品国产二区图片欧美| 久久人妻福利社区极品人妻图片 | 建设人人有责人人尽责人人享有的| 19禁男女啪啪无遮挡网站| av福利片在线| 国产在视频线精品| 国产真人三级小视频在线观看| 最近中文字幕2019免费版| 18禁裸乳无遮挡动漫免费视频| 精品卡一卡二卡四卡免费| 男女无遮挡免费网站观看| 十八禁人妻一区二区| 亚洲欧美日韩高清在线视频 | av网站免费在线观看视频| 黄色毛片三级朝国网站| 少妇被粗大的猛进出69影院| 国产极品粉嫩免费观看在线| 欧美成人午夜精品| a级毛片在线看网站| 丰满少妇做爰视频| 国产熟女欧美一区二区| 一本大道久久a久久精品| 精品久久久久久久毛片微露脸 | 人人妻人人添人人爽欧美一区卜| 美女中出高潮动态图| 99久久精品国产亚洲精品| 欧美性长视频在线观看| 亚洲av在线观看美女高潮| 亚洲欧美一区二区三区黑人| 又粗又硬又长又爽又黄的视频| 亚洲精品成人av观看孕妇| 最黄视频免费看| 亚洲精品国产色婷婷电影| 亚洲精品av麻豆狂野| 看免费av毛片| 久久人人97超碰香蕉20202| 性色av乱码一区二区三区2| 一本色道久久久久久精品综合| 少妇 在线观看| 性高湖久久久久久久久免费观看| av网站在线播放免费| 悠悠久久av| 亚洲九九香蕉| 亚洲欧美一区二区三区久久| 色网站视频免费| 大片免费播放器 马上看| 国产精品.久久久| 久久青草综合色| 久久精品aⅴ一区二区三区四区| 精品国产一区二区久久| 下体分泌物呈黄色| 18禁国产床啪视频网站| 美女主播在线视频| 欧美日韩av久久| 久久久国产精品麻豆| www.熟女人妻精品国产| 久久精品国产a三级三级三级| 久久人妻熟女aⅴ| 久久热在线av| 国产免费又黄又爽又色| 99精品久久久久人妻精品| 下体分泌物呈黄色| 久久女婷五月综合色啪小说| svipshipincom国产片| 亚洲国产成人一精品久久久| 亚洲七黄色美女视频| 脱女人内裤的视频| av欧美777| 免费在线观看黄色视频的| 亚洲欧美一区二区三区国产| 久久国产精品大桥未久av| 制服人妻中文乱码| 日韩视频在线欧美| 成人黄色视频免费在线看| 99国产精品一区二区三区| 国产xxxxx性猛交| 性少妇av在线| 久久久久久免费高清国产稀缺| 男女床上黄色一级片免费看| 又大又黄又爽视频免费| 亚洲国产精品成人久久小说| 国产一区二区三区综合在线观看| 成年女人毛片免费观看观看9 | 99九九在线精品视频| 亚洲精品一二三| 日本色播在线视频| 欧美国产精品va在线观看不卡| 国产成人一区二区在线| 精品一区二区三区四区五区乱码 | 男女床上黄色一级片免费看| 日韩av免费高清视频| 999精品在线视频| 最近最新中文字幕大全免费视频 | 亚洲久久久国产精品| 七月丁香在线播放| 亚洲精品成人av观看孕妇| 亚洲人成77777在线视频| 欧美日韩国产mv在线观看视频| 老司机影院毛片| 中文精品一卡2卡3卡4更新| 999精品在线视频| 日韩一本色道免费dvd| 人人澡人人妻人| 一个人免费看片子| 亚洲一卡2卡3卡4卡5卡精品中文| 国产视频一区二区在线看| 欧美老熟妇乱子伦牲交| 99热网站在线观看| 久久国产精品影院| 大香蕉久久网| 久久午夜综合久久蜜桃| 亚洲人成77777在线视频| 欧美黑人欧美精品刺激| 国产高清videossex| 午夜福利一区二区在线看| 久久久精品94久久精品| 欧美激情 高清一区二区三区| 国产一区二区 视频在线| 亚洲精品美女久久av网站| 亚洲中文日韩欧美视频| 亚洲七黄色美女视频| 水蜜桃什么品种好| 如日韩欧美国产精品一区二区三区| 中文字幕亚洲精品专区| 极品人妻少妇av视频| 在线观看一区二区三区激情| 夫妻午夜视频| 91精品三级在线观看| 一区二区三区四区激情视频| 国产有黄有色有爽视频| 国产精品久久久久久精品电影小说| 亚洲精品日韩在线中文字幕| 婷婷成人精品国产| 国产国语露脸激情在线看| 久久久国产欧美日韩av| 丰满人妻熟妇乱又伦精品不卡| 日日爽夜夜爽网站| 高潮久久久久久久久久久不卡| 日韩制服丝袜自拍偷拍| 中文欧美无线码| 久久久久网色| 国产高清不卡午夜福利| 丁香六月欧美| a级片在线免费高清观看视频| 青春草亚洲视频在线观看| 精品少妇黑人巨大在线播放| 色播在线永久视频| 亚洲国产精品一区二区三区在线| 亚洲中文字幕日韩| av福利片在线| 日本欧美视频一区| 久久ye,这里只有精品| 久久鲁丝午夜福利片| 女人爽到高潮嗷嗷叫在线视频| 天天操日日干夜夜撸| 久久精品久久久久久久性| 亚洲欧美成人综合另类久久久| 国产精品久久久av美女十八| 在线观看国产h片| 日本黄色日本黄色录像| 女人爽到高潮嗷嗷叫在线视频| av网站免费在线观看视频| 妹子高潮喷水视频| 久久久精品国产亚洲av高清涩受| 免费少妇av软件| 久久影院123| 国产免费现黄频在线看| 丝袜脚勾引网站| 午夜av观看不卡| 丝袜在线中文字幕| 亚洲五月婷婷丁香| 在线观看www视频免费| 久久99精品国语久久久| 777久久人妻少妇嫩草av网站| 最近最新中文字幕大全免费视频 | 亚洲第一青青草原| 多毛熟女@视频| 久久精品熟女亚洲av麻豆精品| www.熟女人妻精品国产| 五月开心婷婷网| 国产精品熟女久久久久浪| 十八禁人妻一区二区| www.自偷自拍.com| 夫妻午夜视频| 性高湖久久久久久久久免费观看| 亚洲午夜精品一区,二区,三区| 两性夫妻黄色片| 男女午夜视频在线观看| 欧美精品av麻豆av| 亚洲av电影在线进入| a 毛片基地| 制服诱惑二区| 免费黄频网站在线观看国产| 国产高清videossex| 亚洲中文av在线| 国产片特级美女逼逼视频| 久久性视频一级片| 亚洲国产精品国产精品| 国产片内射在线| 19禁男女啪啪无遮挡网站| 在现免费观看毛片| 日本色播在线视频| 欧美97在线视频| 一级毛片女人18水好多 | 又紧又爽又黄一区二区| 国产麻豆69| 国产av一区二区精品久久| 一级毛片女人18水好多 | 另类精品久久| 中文字幕色久视频| 十八禁网站网址无遮挡| www日本在线高清视频| 亚洲熟女精品中文字幕| av在线老鸭窝| 校园人妻丝袜中文字幕| 亚洲av日韩在线播放| 免费在线观看影片大全网站 | 亚洲av在线观看美女高潮| √禁漫天堂资源中文www| 国产一区二区激情短视频 | 少妇被粗大的猛进出69影院| 大片免费播放器 马上看| 日韩av在线免费看完整版不卡| 黑人巨大精品欧美一区二区蜜桃| 丰满人妻熟妇乱又伦精品不卡| 久久精品人人爽人人爽视色| 亚洲专区国产一区二区| 亚洲伊人久久精品综合| 久久精品熟女亚洲av麻豆精品| 高清不卡的av网站| 母亲3免费完整高清在线观看| 欧美 日韩 精品 国产| 久久久国产一区二区| 啦啦啦 在线观看视频| 亚洲午夜精品一区,二区,三区| 99精品久久久久人妻精品| 久久精品熟女亚洲av麻豆精品| 亚洲精品av麻豆狂野| 亚洲av欧美aⅴ国产| 好男人电影高清在线观看| 免费av中文字幕在线| 夫妻性生交免费视频一级片| 亚洲精品第二区| 国产一区二区在线观看av| 亚洲精品一二三| 婷婷色综合www| 后天国语完整版免费观看| 美女午夜性视频免费| 丁香六月欧美| 中国美女看黄片| 日本五十路高清| 人人澡人人妻人| 满18在线观看网站| 好男人电影高清在线观看| 伦理电影免费视频| 你懂的网址亚洲精品在线观看| 亚洲精品中文字幕在线视频| 高清av免费在线| 90打野战视频偷拍视频| 午夜两性在线视频| 日韩中文字幕视频在线看片| 岛国毛片在线播放| 97精品久久久久久久久久精品| 两人在一起打扑克的视频| 亚洲,欧美精品.| 无限看片的www在线观看| 国产熟女午夜一区二区三区| 一区二区日韩欧美中文字幕| 精品卡一卡二卡四卡免费| 免费人妻精品一区二区三区视频| 天天影视国产精品| av在线播放精品| 麻豆av在线久日| av在线app专区| 久久久久久久精品精品| 老鸭窝网址在线观看| 女人高潮潮喷娇喘18禁视频| 成人18禁高潮啪啪吃奶动态图| 成年美女黄网站色视频大全免费| 丝袜在线中文字幕| 黑人猛操日本美女一级片| 国产有黄有色有爽视频| 国产高清视频在线播放一区 | 黄色怎么调成土黄色| 色94色欧美一区二区| 亚洲国产最新在线播放| 亚洲av日韩在线播放| 国产视频一区二区在线看| 超色免费av| 在线亚洲精品国产二区图片欧美| 菩萨蛮人人尽说江南好唐韦庄| 人妻 亚洲 视频| 天堂8中文在线网| 最近中文字幕2019免费版| 欧美精品亚洲一区二区| 日本午夜av视频| 欧美精品高潮呻吟av久久| 欧美日韩亚洲国产一区二区在线观看 | 久久久久久久久免费视频了| 久久久国产精品麻豆| 老司机影院成人| 在线观看免费日韩欧美大片| 国产成人欧美| 国产激情久久老熟女| 叶爱在线成人免费视频播放| 晚上一个人看的免费电影| 亚洲精品国产色婷婷电影|