单靶磁控溅射Cu(In,Ga)Se_(2)太阳电池的背接触界面设计

通过磁控溅射单一四元靶材磁控得到的黄铜矿Cu(In,Ga)Se_(2)(CIGS)太阳电池开发的主要瓶颈是严重的载流子复合,其开路电压非常低.CIGS与钼(Mo)之间不良的缺陷环境是吸收体和界面复合严重的主要原因之一.其中,在背界面处引入的CuGaSe_(2)(CGS)低温缓冲层可以有效地抑制吸收体与背电极在高温磁控过程中的不利界面反应,从而获得高质量的晶体.通过这种背界面工程,不仅可以很好地解决吸收体和界面质量不佳的问题,而且有利于在吸收层中形成梯度带隙结构,从而使深能级InGa缺陷转换为较低能级的VCu缺陷,最终CIGS太阳电池的转换效率达到15.04%.这项工作为直接溅射高效率CIGS太阳电池的产业化提供了一种新的方法.

Interface optimization and defects suppression via Na F introduction enable efficient flexible Sb_(2)Se_(3) thin-film solar cells

Sb_(2)Se_(3) with unique one-dimensional(1D) crystal structure exhibits exceptional deformation tolerance,demonstrating great application potential in flexible devices.However,the power conversion efficiency(PCE) of flexible Sb_(2)Se_(3) photovoltaic devices is temporarily limited by the complicated intrinsic defects and the undesirable contact interfaces.Herein,a high-quality Sb_(2)Se_(3) absorber layer with large crystal grains and benign [hkl] growth orientation can be first prepared on a Mo foil substrate.Then NaF intermediate layer is introduced between Mo and Sb_(2)Se_(3),which can further optimize the growth of Sb_(2)Se_(3)thin film.Moreover,positive Na ion diffusion enables it to dramatically lower barrier height at the back contact interface and passivate harmful defects at both bulk and heterojunction.As a result,the champion substrate structured Mo-foil/Mo/NaF/Sb_(2)Se_(3)/CdS/ITO/Ag flexible thin-film solar cell delivers an obviously higher efficiency of 8.03% and a record open-circuit voltage(V_(OC)) of 0.492 V.This flexible Sb_(2)Se_(3) device also exhibits excellent stability and flexibility to stand large bending radius and multiple bending times,as well as superior weak light photo-response with derived efficiency of 12.60%.This work presents an effective strategy to enhance the flexible Sb_(2)Se_(3) device performance and expand its potential photovoltaic applications.

Enhanced efficiency of the Sb_(2)Se_(3)thin-film solar cell by the anode passivation using an organic small molecular of TCTA

Antimony selenide(Sb_(2)Se_(3))is an emerging solar cell material.Here,we demonstrate that an organic small molecule of 4,4',4''-tris(carbazol-9-yl)-triphenylamine(TCTA)can efficiently passivate the anode interface of the Sb_(2)Se_(3)solar cell.We fabricated the device by the vacuum thermal evaporation,and took ITO/TCTA(3.0 nm)/Sb_(2)Se_(3)(50 nm)/C60(5.0 nm)/Alq3(3.0 nm)/Al as the device architecture,where Alq3 is the tris(8-hydroxyquinolinato)aluminum.By introducing a TCTA layer,the open-circuit voltage is raised from 0.36 to 0.42 V,and the power conversion efficiency is significantly improved from 3.2%to 4.3%.The TCTA layer not only inhibits the chemical reaction between the ITO and Sb_(2)Se_(3)during the annealing process but it also blocks the electron diffusion from Sb_(2)Se_(3)to ITO anode.The enhanced performance is mainly attributed to the suppression of the charge recombination at the anode interface.

First-principles study on the alkali chalcogenide secondary compounds in Cu(In,Ga)Se_2 and Cu_2ZnSn(S,Se)_4 thin film solar cells

The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.

Performance improvement of CdS/Cu(In,Ga)Se_2 solar cells after rapid thermal annealing

In this paper, we investigated the effect of rapid thermal annealing （RTA） on solar cell performance. An opto-electric conversion efficiency of 11.75% （Voc = 0.64 V, Jsc = 25.88 mA/cm2, FF=72.08%） was obtained under AM 1.5G when the cell was annealed at 300℃ for 30 s. The annealed solar cell showed an average absolute efficiency 1.5% higher than that of the as-deposited one. For the microstructure analysis and the physical phase confirmation, X-ray diffraction （XRD）, Raman spectra, front surface reflection （FSR）, internal quantum efficiency （IQE）, and X-ray photoelectron spectroscopy （XPS） were respectively applied to distinguish the causes inducing the efficiency variation. All experimental results implied that the RTA eliminated recombination centers at the p-n junction, reduced the surface optical losses, enhanced the blue response of the CdS buffer layer, and improved the ohmic contact between Mo and Cu（In, Ga）Se2 （CIGS） layers. This leaded to the improved performance of CIGS solar cell.

Non-ionizing energy loss calculations for modeling electron-induced degradation of Cu(In,Ga)Se_2 thin-film solar cells

The lowest energies which make Cu,In,Ga,and Se atoms composing Cu（In,Ga）Se_2（CIGS） material displaced from their lattice sites are evaluated,respectively.The non-ionizing energy loss（NIEL） for electron in CIGS material is calculated analytically using the Mott differential cross section.The relation of the introduction rate（k） of the recombination centers to NIEL is modified,then the values of k at different electron energies are calculated.Degradation modeling of CIGS thin-film solar cells irradiated with various-energy electrons is performed according to the characterization of solar cells and the recombination centers.The validity of the modeling approach is verified by comparison with the experimental data.

Review on Alkali Element Doping in Cu（In,Ga）Se2 Thin Films and Solar Cells

This paper reviews the development history of alkali element doping on Cu（In,Ga）Se2 （CIGS） solar cells and summarizes important achievements that have been made in this field. The influences of incorporation strategies on CIG5 absorbers and device performances are also reviewed. By analyzing CIGS surface structure and electronic property variation induced by alkali fluoride （NaF and KF） post-deposition treatment （PDT）, we discuss and interpret the following issues： ① The delamination of CIGS thin films induced by Na incorporation facilitates CulnSe2 formation and inhibits Ga during low-temperature co-evaporation process- es. ② The mechanisms of carrier density increase due to defect passivation by Na at grain boundaries and the surface. ③ A thinner buffer layer improves the short-circuit current without open-circuit voltage loss, This is attributed not only to better buffer layer coverage in the early stage of the chemical bath deposition process, but also to higher donor defect （Cd^＋Cu） density, which is transferred from the acceptor defect （C^-cu） and strengthens the buried homojunction. ④ The KF-PDT-induced lower valence band maximum at the absorber surface reduces the recombination at the absorber/buffer interface, which improves the open-circuit voltage and the fill factor of solar cells.

Cu(In,Ga)Se_2薄膜电沉积制备及性能研究

采用Mo/钠钙玻璃衬底作为阴极,饱和甘汞电极(SCE)为参比电极,大面积的铂网电极作为阳极的三电极体系,以氯化铜,三氯化铟,三氯化镓和亚硒酸的水溶液为电解液,利用电沉积技术制备出黄铜矿结构Cu(In,Ga)Se2多晶薄膜。研究了不同热处理温度对C IGS多晶薄膜材料的组成、结构和表面形貌的影响以及薄膜的光电学性能。实验结果表明当热处理温度为450℃时,所制备的Cu(In,Ga)Se2薄膜的化学组成接近理想的化学计量比,薄膜具有黄铜矿结构,颗粒均匀,致密性较好,在室温下禁带宽度为1.43 eV,具有高的吸收系数。

电化学沉积太阳电池用CuInSe_2和Cu(In,Ga)Se_2薄膜的研究进展

综述了电化学沉积太阳电池用CuInSe2(CIS)和Cu(In,Ga)Se2(CIGS)薄膜的研究和发展;对CIS和CIGS预制层的电化学沉积路线,包括一步沉积、分步沉积和特种电沉积的研究进展进行了详细的评述;综述了电沉积预制层的后处理,包括退火、化学处理和PVD调整成分的研究状况。回顾了基于电化学沉积的CIS和CIGS太阳电池研究的发展过程,并介绍了目前实验室和产业化研究的最新成果,指出了存在的问题并展望了其发展趋势。

Cu(In,Ga)Se_2薄膜太阳电池二极管特性的研究

本文采用线性拟合光态和暗态J-V(电流-电压)曲线的方法计算了不同效率的Cu(In,Ga)Se2(CIGS)薄膜太阳电池的二极管性能参数。在一定范围内,CIGS薄膜电池的二极管品质因子A和反向饱和电流J0值越小,电池的转换效率越高,这说明CIGS电池的复合主要发生在PN结区内。量子效率分析表明,不同效率的CIGS电池在短波区(λ<520nm)的光谱响应相差不大,而在长波区(520～1100nm),低效率电池存在很大的吸收,这是由低质量的CIGS吸收层造成的。这进一步验证了光-暗态J-V曲线的分析结果,即高质量的吸收层是制备CIGS电池的关键。

柠檬酸钠的浓度对电沉积制备Cu(In,Ga)Se_2薄膜的影响(英文)

本文详细介绍了电沉积制备Cu(In,Ga)Se2(CIGS)薄膜的原理。电解液由CuCl2,InCl3,GaCl3和柠檬酸钠溶液组成。溶流组成通过改变柠檬酸钠的浓度,铟和镓的沉积电位接近或等于铜和硒的沉积电位。Cu(In,Ga)Se2薄膜的性能研究分别采用扫描电镜自带能谱仪(EDS)、X射线衍射(XRD)和扫描电镜分析Cu(In,Ga)Se2薄膜的化学组成、晶体结构和表面形貌。结果表明当柠檬酸钠浓度为1.0M时,所制备的Cu(In,Ga)Se2薄膜为单一的黄铜矿结构,晶粒大小均匀。

多晶Cu(In,Ga)Se_2薄膜太阳电池光强特性的研究

本文系统研究了Cu（In,Ga）Se2（CIGS）薄膜太阳电池在入射光强为10-100 mW/cm^2范围内的性能参数。结果表明,随光强的减弱,CIGS电池的转换效率、填充因子、短路电流密度和开路电压等性能参数逐步衰减;电池参数与光强的依赖关系可明显划分为两个阶段：光强高于75 mW/cm^2时,电池性能变化不大;当光强低于70 mW/cm^2时,电池性能衰减明显。这是由于随着光强的降低,RS（串联电阻）值和RSH（并联电阻）值都在升高。其中,RSH值的增大使得CIGS电池的弱光特性变好,但较小的RSH值并不能弥补RS所导致电池性能的衰退。最后,发现高Ga含量的CIGS薄膜电池（8.7%）比低Ga含量（6.9%）的电池弱光特性好。

Cu(In,Ga)Se_2太阳电池缓冲层ZnS薄膜性质及应用

在含有ZnSO4,SC(NH2)2,NH4OH的水溶液中采用CBD法沉积ZnS薄膜,XRF和热处理前后的XRD测试表明,ZnS沉积薄膜为立方相结构,薄膜含有非晶态的Zn(OH)2.光学透射谱测试表明,制备的薄膜透过率(λ>500nm)约为90%,薄膜的禁带宽度约为3·51eV.ZnS薄膜沉积时间对Cu(In,Ga)Se2太阳电池影响显著,当薄膜沉积时间在25～35min时,电池的综合性能最好.对比了不同缓冲层的电池性能,采用CBD-CdS为缓冲层的电池转换效率、填充因子、开路电压稍高于CBD-ZnS为缓冲层的无镉电池,但无镉电池的短路电流密度高于前者,两者转换效率相差2%左右.ZnS可以作为CIGS电池的缓冲层,替代CdS,实现电池的无镉化.

Interpenetrating structure for efficient Sb_(2)Se_(3) nanorod array solar cells loaded with CuInSe_(2) QDs sensitizer

The strong anisotropic electrical properties of one-dimensional(1 D) nanostructure semiconductors,especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb_(2)Se_(3) nanorod array with highly(hk1) orientation on Cd S substrate, and constructed superstrate nanorod solar cells for the first time. The Sb_(2)Se_(3) nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe_(2) quantum dots(QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe_(2) QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe_(2) / Sb_(2)Se_(3) solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb_(2)Se_(3) nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb_(2)Se_(3) nanorod arrays.

基于机器学习和器件模拟对Cu(In,Ga)Se_(2)电池中Ga含量梯度的优化分析

Cu(In,Ga)Se_(2)(CIGS)太阳能电池是一种高效薄膜太阳能电池,Ga含量(Ga/(Ga+In),GGI)梯度调控是在不损失短路电流情况下,获得高开路电压的一种有效方法.本文基于对薄膜电池效率极限的对比分析,首先评估了CIGS电池性能提升的优化空间和策略.进而,通过机器学习与电池模拟分析相结合,研究了不同类别的“V”型GGI梯度对电池性能的影响,优化了“V”型双梯度的分布,获得了高于26%的模拟效率,并探究了其内部载流子作用机理.本文的研究提供了获得高效率CIGS电池“V”型GGI梯度的优化方案,为实验优化提供了指导.

Lithium-assisted synergistic engineering of charge transport both in GBs and GI for Ag-substituted Cu2ZnSn(S,Se)4 solar cells

Although silver(Ag) substitution offers several benefits in eliminating bulk defects and facilitating interface type inversion for Cu2ZnSn(S,Se)4(CZTSSe) photovoltaic(PV) technology, its further development is still hindered by the fairly low electrical conductivity due to the significant decrease of acceptors amount.In this work, a versatile Li–Ag co-doping strategy is demonstrated to mitigate the poor electrical conductivity arising from Ag through direct incorporating Li via postdeposition treatment(PDT) on top of the Ag-substituted CZTSSe absorber. Depth characterizations demonstrate that Li incorporation increases ptype carrier concentration, improves the carrier collection within the bulk, reduces the defects energy level as well as inverts the electric field polarity at grain boundaries(GBs) for Ag-substituted CZTSSe system. Benefiting from this lithium-assisted complex engineering of electrical performance both in grain interior(GI) and GBs, the power conversion efficiency(PCE) is finally increased from 9.21% to 10.29%. This systematic study represents an effective way to overcome the challenges encountered in Ag substitution,and these findings support a new aspect that the synergistic effects of double cation dopant will further pave the way for the development of high efficiency kesterite PV technology.

Photovoltaic properties of Cu_2O-based heterojunction solar cells using n-type oxide semiconductor nano thin films prepared by low damage magnetron sputtering method

We improved the photovoltaic properties of Cu_2O-based heterojunction solar cells using n-type oxide semiconductor thin films prepared by a sputtering apparatus with our newly developed multi-chamber system. We also obtained the highest efficiency(3.21%) in an AZO/p-Cu_2O heterojunction solar cell prepared with optimized pre-sputtering conditions using our newly developed multi-chamber sputtering system. This value achieves the same or higher characteristics than AZO/Cu_2O solar cells with a similar structure prepared by the pulse laser deposition method.

Interfaces of high-efficiency kesterite Cu_2ZnSnS(e)_4 thin film solar cells

Cu2ZnSnS（e）4 （CZTS（e）） solar cells have attracted much attention due to the elemental abundance and the non- toxicity. However, the record efficiency of 12.6% for CuzZnSn（S,Se）4 （CZTSSe） solar cells is much lower than that of Cu（In,Ga）See （CIGS） solar cells. One crucial reason is the recombination at interfaces. In recent years, large amount inves- tigations have been done to analyze the interfacial problems and improve the interfacial properties via a variety of methods. This paper gives a review of progresses on interfaces of CZTS（e） solar cells, including： （i） the band alignment optimization at buffer/CZTS（e） interface, （ii） tailoring the thickness of MoS（e）2 interfacial layers between CZTS（e） absorber and Mo back contact, （iii） the passivation of rear interface, （iv） the passivation of front interface, and （v） the etching of secondary phases.

Precisely tuning Ge substitution for efficient solution-processed Cu_2ZnSn(S,Se)_4 solar cells

The kesterite Cu2ZnSn（S,Se）4 （CZTSSe） solar cells have yielded a prospective conversion efficiency among all thin- film photovoltaic technology. However, its further development is still hindered by the lower open-circuit voltage （Voc）, and the non-ideal bandgap of the absorber is an important factor affecting this issue. The substitution of Sn with Ge provides a unique ability to engineer the bandgap of the absorber film. Herein, a simple precursor solution approach was successfully developed to fabricate Cu2Zn（SnyGel_y）（SxSe~ x）4 （CZTGSSe） solar cells. By precisely adjusting the Ge content in a small range, the Voc and Jsc are enhanced simultaneously. Benefitting from the optimized bandgap and the maintained spike structure and light absorption, the 10% Ge/（Ge＋Sn） content device with a bandgap of approximately 1.1 eV yields the highest efficiency of 9.36%. This further indicates that a precisely controlled Ge content could further improve the cell performance for efficient CZTGSSe solar cells.

Boosting Cu(In,Ga)Se_(2)Thin Film Growth in Low-Temperature Rapid-Deposition Processes:An Improved Design for the Single-Heating Knudsen Effusion Cell

The Knudsen effusion cell is often used to grow high-quality Cu(In,Ga)Se_(2)(CIGS)thin film in coevaporation processes.However,the traditional single-heating Knudsen effusion cell cannot deliver complete metal selenides during the whole deposition process,particularly for a low-temperature deposition process,which is probably due to the condensation and droplet ejection at the nozzle of the crucible.In this study,thermodynamics analysis is conducted to decipher the reason for this phenomenon.Furthermore,a new single-heating Knudsen effusion is proposed to solve this difficult problem,which leads to an improvement in the quality of CIGS film and a relative increase in conversion efficiency of 29%at a growth rate of about 230 nmmin1,compared with the traditional efficiency in a lowtemperature rapid-deposition process.