Effect of Defects at the Buffer Layer CdS/Absorber CIGS Interface on CIGS Solar Cell Performance

This scientific paper presents a study investigating the effects of defects at the CdS/CIGS and CdS/SDL interfaces on the performance of CIGS solar cells. The objective of this study is to analyze the influence of defects at the interface between the CdS buffer layer and the CIGS absorber, as well as the surface defect layer (SDL), on CIGS solar cell performance. The study explores three key aspects: the impact of the conduction band offset (CBO) at the CdS/CIGS interface, the effects of interface defects and defect density on performance, and the combined influence of CBO and defect density at the CdS/ SDL and SDL/CIGS interfaces. For interface defects not exceeding 1013 cm-2, we obtained a good efficiency of 22.9% when -0.1 eV analyzing the quality of CdS/SDL and SDL/CIGS junctions, it appears that defects at the SDL/CIGS interface have very little impact on the performances of the CIGS solar cell. By optimizing the electrical parameters of the CdS/SDL interface defects, we achieved a conversion efficiency of 23.1% when -0.05 eV < CBO < 0.05 eV.

Lattice structures and electronic properties of CIGS/CdS interface:First-principles calculations

Using first-principles calculations within density functional theory, we study the atomic structures and electronic properties of the perfect and defective （2VCu＋ Incu） CulnGaSe2/CdS interfaces theoretically, especially the interface states. We find that the local lattice structure of （2VCu＋ InCu） interface is somewhat disorganized. By analyzing the local density of states projected on several atomic layers of the two interfaces models, we find that for the （2VCu＋InCu） interface the interface states near the Fermi level in CulnGaSe2 and CdS band gap regions are mainly composed of interracial Se-4p, Cu-3d and S-3p orbitals, while for the perfect interface there are no clear interface states in the CulnGaSe2 region but only some interface states which are mainly composed of S-3p orbitals in the valance band of CdS region.

Peanut-chocolate-ball-inspired construction of the interface engineering between CdS and intergrown Cd:Boosting both the photocatalytic activity and photocorrosion resistance

Interface engineering can improve the charge separation efficiency and inhibit photocorrosion is an emerging direction of developing more efficient and cost-effective photocatalytic systems.Herein,we report the sulfur-confined intimate Cd S intergrown Cd(Cd S/Cd)Ohmic junction(peanut-chocolate-ball like)for high-efficient H2production with superior anti-photocorrosion ability,which was fabricated from in-situ photoreduction of CdS intergrown Cd2SO4(OH)2(CdS/Cd2SO4(OH)2)prepared through a facile space-controlled-solvothermal method.The ratios of CdS/Cd can be effectively controlled by tunning that of CdS/Cd2SO4(OH)2which were prepared by adjusting the volume of reaction liquid and the remaining space of the reactor.Experiments investigations and density functional theory(DFT)calculations reveal that the Cd S intergrown Cd Ohmic junction interfaces(with appropriate content Cd intergrown on Cd S(19.54 wt%))are beneficial in facilitating the transfer of photogenerated electrons by constructing an interfacial electric field and forming sulfur-confined structures for preventing the positive holes(h+)oxidize the Cd S.This contributes to a high photocatalytic H2production activity of 95.40μmol h-1(about 32.3 times higher than bare Cd S)and possesses outstanding photocatalytic stability over 205 h,much longer than most Cd S-based photocatalysts previously reported.The interface engineering design inspired by the structure of peanut-chocolate-ball can greatly promote the future development of catalytic systems for wider application.

Reduced Recombination Current Due to Sputtered CdO Nanolayer at CdS/CdTe Interface

In this paper, interface engineering via sputtering of CdO nanolayer at the buffer-CdS/CdTe-absorber interface is demonstrated as an efficient approach to improve the performance of solar cell device. The i-CdO interfacial layer with various thicknesses from 5 nm to 35 nm was deposited by DC magnetron sputtering. Comparative studies on TCO/CdS/CdTe and TCO/CdS/CdO/CdTe interfaces have been conducted by current-voltage, capacitance-voltage and admittance spectroscopy measurements. The current-voltage characteristics of the devices with an area of 0.45 cm2 under 100 mW/cm2 illumination, at the optimum thickness of CdO intermediate layer in the proposed structures, show increases of the short circuit current density and the open circuit voltage by 5% and 25%, respectively. The efficiency improvement of 3.1% of p-i-n cell over p-n cell is observed. Results of the temperature-dependent current-voltage and admittance measurements revealed the removing of the deep level defect with the activation energy of 0.43 eV and the reducing of the ideality factor from 1.9 to 1.8 via buffer/absorber interfacial passivation method. Interface passivation appears to be critical to improve the short circuit current density and the open circuit voltage, and CdO thin film is clearly effective for this purpose.

CIGS电池缓冲层CdS的制备工艺及物理性能

在含有醋酸镉、醋酸氨、硫脲和氨水的水溶液中，化学沉积CdS半导体薄膜，薄膜的厚度与搅拌强度有很大关系，表明薄膜的生长速度是由OH^-和SC（NH2）2的扩散传质为控制步骤。CAS薄膜的电阻率在10^4-- 10^5Ω·Cm之间。CAS薄膜的品格在乙酸胺浓度较小时，为六方晶和立方晶混合结构；乙酸胺浓度较大时，为立方晶结构。利用六方晶与立方晶混合的CAS制备的CIGS太阳电池，光电转换效率最大可达12．1％，3．5×3．6cm^3小面积组件为6．6％。立方相CAS制备的最佳电池效率达到12．17％。两种晶相结构的CAS薄膜对CIGS太阳电池的性能影响没有明显的差别。

CdS薄膜的真空热蒸发制备及在CIGS薄膜太阳电池中的应用

采用真空热蒸发（VTE）的方法制备了CdS多晶薄膜，研究了不同衬底温度对其微观结构与光电性能的影响。结果显示，不同衬底温度下制备的CdS薄膜均属于六方相多晶结构且具有（002）择优取向；随着衬底温度的升高，（002）特征衍射峰强度增加，半高宽变小，相应薄膜结晶度增大；由CdS薄膜的透射光谱可知，在5001000nm波段平均透过率均超过80％，光学带隙随着衬底温度的升高而增大（2．44～2．56eV），表明真空热蒸发方法制备的CdS薄膜可以作为CIGS薄膜太阳电池的缓冲层。将真空热蒸发法制备CdS薄膜与磁控溅射法制备CIGS薄膜太阳电池相结合，在同一真空室内得到了CIGS薄膜太阳电池器件，为CIGS薄膜太阳电池的工业化推广提供了新途径。

A 9% efficiency of flexible Mo-foil-based Cu2ZnSn(S,Se)4 solar cells by improving CdS buffer layer and heterojunction interface

Flexible Cu2ZnSn(S,Se)4(CZTSSe)solar cells show great potential applications due to low-cost,nontoxicity,and stability.The device performances under an especial open circuit voltage(VOC)are limited by the defect recombination of CZTSSe/CdS heterojunction interface.We improve the deposition technique to obtain compact CdS layers without any pinholes for flexible CZTSSe solar cells on Mo foils.The efficiency of the device is improved from 5.7%to 6.86%by highquality junction interface.Furthermore,aiming at the S loss of CdS film,the S source concentration in deposition process is investigated to passivate the defects and improve the CdS film quality.The flexible Mo-foil-based CZTSSe solar cells are obtained to possess a 9.05%efficiency with a VOC of 0.44 V at an optimized S source concentration of 0.68 mol/L.Systematic physical measurements indicate that the S source control can effectively suppress the interface recombination and reduce the VOCdeficit.For the CZTSSe device bending characteristics,the device efficiency is almost constant after1000 bends,manifesting that the CZTSSe device has an excellent mechanical flexibility.The effective improvement strategy of CdS deposition is expected to provide a new perspective for promoting the conversion efficiency of CZTSSe solar cells.

Forward and reverse electron transport properties across a CdS/Si multi-interface nanoheterojunction

The electron transport behavior across the interface plays an important role in determining the performance of op- toelectronic devices based on heterojunctions. Here through growing CdS thin film on silicon nanoporous pillar array, an untraditional, nonplanar, and multi-interface CdS/Si nanoheterojunction is prepared. The current density versus voltage curve is measured and an obvious rectification effect is observed. Based on the fitting results and model analyses on the forward and reverse conduction characteristics, the electron transport mechanism under low forward bias, high forward bias, and reverse bias are attributed to the Ohmic regime, space-charge-limited current regime, and modified Poole-Frenkel regime respectively. The forward and reverse electrical behaviors are found to be highly related to the distribution of inter- facial trap states and the existence of localized electric field respectively. These results might be helpful for optimizing the preparing procedures to realize high-performance silicon-based CdS optoelectronic devices.

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.

Comparative Study of the Effect of Shading Rate on the Electrical Parameters of CIGS and CdTe/CdS Solar Modules

In this paper, a comparative study of the maximum power on the shading rate on the maximum power of thin film PV modules. Thus two thin film PV modules of type Copper indium gallium selenide, CIGS, of 90W power and a CdTe (Cadmium telluride)/CdS (Cadmium sulfide) module, of maximum power 75 W. These modules, reference SN-CIGS90 and CX3 75 were tested under the conditions of the installation site to ensure their proper functioning and to determine the initial values of electrical parameters before shading. The results obtained are as follows: for the CIGS: Pm (80.717 W);Vco (23.06 V), Icc (3.5 A) and for the CdTe:Pm (54.914 W);Vco (35.52 V), Icc (1.546 A). After this characterization test, the modules are exposed to real operating conditions at the Center for Study and Research on the renewable energy (CERER), Cheikh Anta Diop University in Dakar. Four types of shading are performed on each module with the same mask: partial shading at 25%, 50%, 75% and complete shading at 100%. The comparison of the variation rates obtained on the experimental values of the 4 types of shading carried out on each module, shows that, the phenomenon of shading constitutes an environmental factor which influences negatively the maximum power of the thin film PV modules. But this reduction depends on the surface of the shaded module, the nature of the mask but also the technology used. Indeed, for a shading of 25% of the surface of the two modules, we note a reduction of 21.32% of power for the CIGS, against 40.53% for the CdTe/CdS, that is to say a difference which approaches 20%.

Photoelectrochemical Studies at CdS/PTTh Nanoparticles Interfaces

Photo-activities at Inorganic/Organic/Interfaces (IOI) consisting of CdS/ Polyterthiophine (PTTh) assemblies were investigated in nanoparticle suspension and in thin solid film forms. The effects PTTh modifier cause on the photoelec-trochemical behavior of the IOI were investigated using [Fe(CN)6]4- as photoactive hydrated electron donor agent. Results show that the adsorption process of [Fe(CN)6]3- (photolysis product) control the photoactivity outcome of IOI assemblies. CdS/PTTh shows lower heterogeneous photochemical response than native CdS. Native CdS amorphous nanoparticles adsorb more [Fe(CN)6]3- with very steady adsorption /desorption process than the modified ones. The interface activities were explained by analyzing the IOI junctions’ characteristics, such as electron affinity, work function and hole/electrons barrier heights. The aqueous nano-systems retained moderate stability as indicated by the reproducibility of their photocatalytic activities. Both [Fe(CN)6]4- and PTTh contributed to the stability of native CdS surfaces.

Lattice structures and electronic properties of WZ-CuInS2/WZ-CdS interface from first-principles calculations

Using the first-principles plane-wave calculations within density functional theory, the perfect bi-layer and monolayer terminated WZ-CIS （100）/WZ-CdS （100） interfaces are investigated. After relaxation the atomic positions and the bond lengths change slightly on the two interfaces. The WZ-CIS/WZ-CdS interfaces can exist stably, when the interface bonding energies are -0.481 J/m2 （bi-layer terminated interface） and -0.677 J/m2 （monolayer terminated interface）. Via analysis of the density of states, difference charge density and Bader charges, no interface state is found near the Fermi level. The stronger adhesion of the monolayer terminated interface is attributed to more electron transformations and orbital hybridizations, promoting stable interfacial bonds between atoms than those on a bi-layer terminated interface.

CIGS薄膜太阳能电池缓冲层CdS薄膜的制备研究

目前CdS材料的制备方法有很多种,但是最常用的是化学水浴法。本文研究了浓度、反应溶液pH值、温度、沉积时间对CdS缓冲层薄膜的影响,对CIGS薄膜太阳能电池缓冲层CdS薄膜的制备方法进行了论述。

Required CIGS and CIGS/Mo Interface Properties for High-Efficiency Cu(In, Ga)Se<SUB>2</SUB>Based Solar Cells

In this work, we have modeled and simulated the electrical performance of CIGS thin-film solar cell using one-dimensional simulation software (SCAPS-1D). Starting from a baseline model that reproduced the experimental results, the properties of the absorber layer and the CIGS/Mo interface have been explored, and the requirements for high-efficiency CIGS solar cell were proposed. Simulation results show that the band-gap, acceptor density, defect density are crucial parameters that affect the performance of the solar cell. The best conversion efficiency is obtained when the absorber band-gap is around 1.2 eV, the acceptor density at 1016 cm−3 and the defect density less than 1014 cm−3. In addition, CIGS/Mo interface has been investigated. It appears that a thin MoSe2 layer reduces recombination at this interface. An improvement of 1.5 to 2.5 mA/cm2 in the current density (Jsc) depending on the absorber thickness is obtained.

The Effect of Lymphocyte Immunotherapy on CD80^+ Cells at the Fetomaternal Interface and Cyesis Result of Mice Model of Spontaneous Abortion

Objectives To explore the relationship between CD80 expression on lymphocytes at the fetomaternal interface and the fertility characteristics in CBA/J×DBA/2 mice as a model of recurrent spontaneous abortion (RSA) and to investigate the effects of lymphocyte immunotherapy (LIT) on the level of CD80 expression. Materials & Methods The characteristics of fertility in CBA/J×DBA/2 mice were observed in a 120 day period and compared with four normal fertile groups. In another 15 pairs of CBA/J×DBA/2 breedings, resorption rate on day 13 of pregnancy were calculated and the proportion of CD80 + cells at the fetomaternal interface were determined by using two color flow cytometric analysis, mainly stained with CD80 FITC and CD45 PE. In order to determine the identity of CD80 + cells, the expression levels of CD3(T cell marker), DX5(NK cell marker), and MHC II(antigen presenting cell marker) were detected in this cell population. Furthermore, the resorption rate and the proportion of CD80 + cells among CBA/J×DBA/2 breedings with and without immunotherapy were also determined and compared with normal fertile controls. Results The characteristics of abortion in CBA/J×DBA/2 mice were recurrent abortion on about day 10 of gestation. The resorption rate in CBA/J×DBA/2 mice was significantly higher than that in BALB/c×DBA/2 mice (30.8%±16.6% vs. 7.7%±6.7%, P<0.01). Accordingly, the proportion of CD80 + cells evaluated at the fetomaternal interface in CBA/J×DBA/2 mice was also significantly higher (11.7% ±5.8% vs. 3.9%±1.8%, P<0.01). Resorption rate of CBA/J×DBA/2 mice underwent of LIT was significantly lower than that without LIT, and this decreased rate was correlated with decreased proportion of CD80 + cells. Conclusion In CBA/J×DBA/2 mice model, the characteristics of abortion seem to be peri implantation embryo resorption. A correlation between early embryonic waste and higher CD80 proportion at the fetomaternal interface suggests that CD80 + cells may be an important determinant in recurrent peri implantation abortion.

纳米颗粒墨水法制备的CIGSSe太阳能电池Cu含量调控与仿真模拟

利用实验加仿真模拟的方法探究了纳米颗粒墨水中Cu含量(Cu/In+Ga,CGI)对铜铟镓硫硒(CIGSSe)太阳能电池性能的影响。首先,通过不同CGI墨水制备了CIGSSe太阳能电池器件,并对其吸收层进行了SEM,霍尔效应,以及拉曼光谱表征。表征结果表明:随着铜含量上升,吸收层晶体生长状况逐渐改善,且载流子浓度也逐步增大,但吸收层表面却存在越发明显的Cu2-xSe杂相。实验得出当吸收层的CGI为1.03时,器件的能量转换效率(PCE)最高,达10.09%。随后建立了对应的器件仿真模型,获得了具有不同CGI的CIGSSe器件的能量转换效率、器件能带与复合率分布情况,模拟结果表明:随着铜含量提高,载流子浓度上升,器件的开路电压有所提升,但当载流子浓度超过1018 cm-3时,吸收层表面出现了陡峭的能带弯曲现象,这增大了隧穿界面复合的发生,从而影响了器件的能量转换效率。因此,由实验与仿真模拟表明:制备CIGSSe薄膜太阳能电池时,有必要对Cu含量进行调控,从而达到促进晶体生长,减少界面复合,提升器件能量转换效率的目的。

化学水浴沉积CdS薄膜晶相结构及性质

采用CBD法在醋酸镉溶液体系中制备CdS半导体薄膜,研究了溶液组份的浓度对CdS结晶结构的影响.增加乙酸胺的浓度、提高溶液的pH值有利于生成立方晶CdS,反之则易于生成六方晶CdS.无论立方相还是六方相CdS薄膜,电阻率均在104～105Ω·cm范围,结晶均匀细致.用六方晶为主和立方晶为主的CdS制备的CIGS太阳电池最高效率分别达到12.10%和12.17%.

化学水浴沉积时间对CdS薄膜性质的影响

采用CBD法在醋酸镉溶液体系中制备CdS半导体薄膜,通过XRD、XRF、SEM和光学透过率谱等测试手段研究了沉积时间对CdS薄膜沉积过程和性质的影响。结果表明,随着沉积时间的增加,薄膜增厚;S/Cd原子比增加,但都为富Cd的CdS薄膜;XRD研究表明,薄膜结构由立方、六方混合相向立方相转变,(111)方向成为择优生长方向;SEM研究表明,随沉积时间增加,薄膜变致密,薄膜表面出现的白色附着颗粒增多,尺寸增大;沉积时间对薄膜的光学性质也有很大的影响,随着沉积时间的增加薄膜透过率减小,而禁带宽度值增大。

衬底温度对PLD法沉积CdS及ZnS薄膜材料的影响

以ITO玻璃为衬底,利用脉冲激光沉积(PLD)法在温度为50、200和400℃下制备了CdS、ZnS薄膜。测量分析了温度对CdS及ZnS薄膜的透射光谱特性、光学带隙、Raman光谱特性等的影响。结果显示,在实验温度范围内:①ZnS薄膜比CdS薄膜透射性能好,光学带隙大;②ZnS薄膜的Raman光谱复杂,Raman特征峰较弱;CdS薄膜的Raman特征峰明显;③随温度升高,CdS与ZnS相比禁带宽度增加明显、Raman特征峰增高变窄。对此现象进行了解释,为利用CdS或ZnS薄膜作为CIGS薄膜太阳电池缓冲层提供了参考。

CIGS薄膜太阳能电池缓冲层的研究及其发展

本论述简要介绍了CIGS薄膜太阳能电池缓冲层的发展,重点阐述了CdS和ZnS缓冲层的研究现状,指出缓冲层的制备工艺上以化学水浴法居多,从成膜机理到工艺参数的优化都做了充分的研究,对真空蒸发法的制备工艺研究则相对较少,而且大部分都集中在蒸发温度、衬底温度和沉积温度对薄膜性能的影响上。最后指出了发展过程中遇到的两个问题:一Cd对环境的污染,二化学水浴法不利于工业化大生产。